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  • Articles  (144)
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  • Column liquid chromatography  (124)
  • nitric oxide
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  • Articles  (144)
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  • Springer  (144)
  • American Geophysical Union
  • Cell Press
  • International Union of Crystallography
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  • 1
    Electronic Resource
    Electronic Resource
    Catalytic disruption and volatilization of rhodium particles on silica in NO + CO (1992)
    Springer
    Catalysis letters 14 (1992), S. 141-148 
    Details
    ISSN: 1572-879X
    Keywords: Rhodium ; silica ; catalyst microstructure ; disruption ; carbon monoxide ; nitric oxide ; model catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Initially reduced ≈ 100 Å diameter Rh metal particles on SiO2 are found by TEM to be dispersed into an amorphous metal film by treatment in 5% NO + 5% CO in He at 260 °C, leaving thin rings around the perimeter of the original particles. Electron diffraction shows that Rh is amorphous while XPS shows that the Rh is approximately zero valent in the dispersed state. Continued heating in this mixture resulted in irreversible volatilization of the Rh even at these low temperatures. Subsequent heating in H2 at 650 °C caused sintering and the reformation of crystalline Rh particles, but with a lower loading than observed initially. Treatment of Rh particles in 5% NO at 260 °C causes Rh particles to shrink in diameter and to form thin shells around their perimeters. The only change observed after treatment in 5% CO alone at 260 °C was slight sintering of adjacent Rh particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765228
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  • 2
    Electronic Resource
    Electronic Resource
    Composition of Pd-La/α-Al2O3 catalysts (1992)
    Springer
    Catalysis letters 16 (1992), S. 323-334 
    Details
    ISSN: 1572-879X
    Keywords: Palladium ; lanthanum ; lanthanum oxide ; lanthanum aluminum oxide ; α-alumina ; X-ray diffraction (XRD) ; temperature-programmed reduction (TPRd) ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The objective of this study is to investigate the structure of the Pd-La/α-Al2O3 catalyst. X-ray diffraction (XRD) and temperature-programmed reduction (TPRd) were used as characterization techniques. Contrary to the assertions in the literature, XRD studies conducted on La/α-Al2O3 composite oxides and Pd-La/α-Al2O3 catalysts show that Pd catalyzes the solid state reaction between A12O3 and Al2O3 to form LaAlO3. TPRd studies conducted on Pd/α-Al2O3, Pd/La2O3, Pd/LaAlO3, and Pd-La/α-Al2O3 catalysts suggest that Pd in the Pd-La/α-Al2O3 catalyst interacts more strongly with LaAlO3 than with α-Al2O3. Reaction studies were conducted to investigate the activity of Pd/α-Al2O3, Pd/La2O3, Pd/LaA103, and Pd-La/α-Al2O3 catalysts for nitric oxide (NO) reduction. These studies show that Pd/LaAlO3 catalysts are most active for NO removal at stoichiometric and under net reducing conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764344
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  • 3
    Electronic Resource
    Electronic Resource
    Simultaneous catalytic reduction of sulfur dioxide and nitric oxide (1999)
    Springer
    Catalysis letters 62 (1999), S. 127-130 
    Details
    ISSN: 1572-879X
    Keywords: simultaneous reduction ; sulfur dioxide ; nitric oxide ; carbon monoxide ; carbonyl sulfide ; lanthanum oxysulfide ; cobalt disulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The present work reports a catalytic system for the simultaneous reduction of SO2 and NO using CO as a reducing agent. The catalyst contains lanthanum oxysulfide and cobalt sulfides. Experimental results showed that at temperature above 450°C, SO2 and NO conversions are greater than 98 and 99%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019075828527
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  • 4
    Electronic Resource
    Electronic Resource
    Selective catalytic reduction of nitric oxide with ammonia on Mn‐promoted carbonized used silica–alumina sorbents (1999)
    Springer
    Catalysis letters 63 (1999), S. 107-111 
    Details
    ISSN: 1572-879X
    Keywords: selective catalytic reduction ; nitric oxide ; ammonia ; Mn‐promoted silica–alumina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Deactivated (waste) silica–alumina sorbents were carbonized and used as supports. The introduction of manganese led to active and selective SCR catalysts at low temperatures. Two methods of Mn promoting were compared: wet impregnation and adsorption. They influenced the distribution of Mn and N2O production. The catalysts behaved similarly to Mn‐promoted active carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019056718957
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  • 5
    Electronic Resource
    Electronic Resource
    Changes of sodium and ATP affinities of the cardiac (Na,K)-ATase during and after nitric oxide deficient hypertension (1999)
    Springer
    Molecular and cellular biochemistry 202 (1999), S. 141-147 
    Details
    ISSN: 1573-4919
    Keywords: (Na,K)-ATPase ; Na+-binding site ; nitric oxide ; hypertension ; L-NAME ; cardiac sarcolemma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In the cardiovascular system, NO is involved in the regulation of a variety of functions. Inhibition of NO synthesis induces sustained hypertension. In several models of hypertension, elevation of intracellular sodium level was documented in cardiac tissue. To assess the molecular basis of disturbances in transmembraneous transport of Na+, we studied the response of cardiac (Na,K)-ATPase to NO-deficient hypertension induced in rats by NO-synthase inhibition with 40 mg/kg/day NG-nitro-L-arginine methyl ester (L-NAME) for 4 four weeks. After 4-week administration of L-NAME, the systolic blood pressure (SBP) increased by 36%. Two weeks after terminating the treatment, the SBP recovered to control value. When activating the (Na,K)-ATPase with its substrate ATP, no changes in Km and Vmax values were observed in NO-deficient rats. During activation with Na+, the Vmax remained unchanged, however the KNa increased by 50%, indicating a profound decrease in the affinity of the Na+-binding site in NO-deficient rats. After recovery from hypertension, the activity of (Na,K)-ATPase increased, due to higher affinity of the ATP-binding site, as revealed from the lowered Km value for ATP. The KNa value for Na+ returned to control value. Inhibition of NO-synthase induced a reversible hypertension accompanied by depressed Na+-extrusion from cardiac cells as a consequence of deteriorated Na+-binding properties of the (Na,K)-ATPase. After recovery of blood pressure to control values, the extrusion of Na+ from cardiac cells was normalized, as revealed by restoration of the (Na,K)-ATPase activity. (Mol Cell Biochem 000: 000-000, 1999)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007097617502
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  • 6
    Electronic Resource
    Electronic Resource
    Role of nitric oxide in the induction of apoptosis by smokeless tobacco extract (1999)
    Springer
    Molecular and cellular biochemistry 200 (1999), S. 51-57 
    Details
    ISSN: 1573-4919
    Keywords: smokeless tobacco ; apoptosis ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Smokeless tobacco usage is, a growing public health concern in the United States. Lesions of the oral cavity have been clearly linked to smokeless tobacco use. The objective of this study was to determine the biochemical effects of smokeless tobacco extract (STE) exposure upon hamster cheek pouch cell (HCPC-1) cultures. HCPC-1 cells were exposed to a 5 -fold dose-range of STE (0.5, 1.0 and 2.5%) over a time-course of 24-96 h. Following each exposure we measured various biochemical parameters of cell proliferation and cell death. Cell viability, cell cycle progression and S-phase DNA synthesis were measured as markers of cell proliferation. We measured lactate dehydrogenase leakage as a marker of cell membrane damage and cell death due to necrosis. No significant alterations were observed in cell cycle progression and cell proliferation as a result of exposure to STE. LDH measured colorimetrically indicated no significant effect with the lower doses (0.5, 1.0 and 2.5% STE). Apoptosis measured as the A0 peak and by the TUNEL procedure revealed that STE caused significant rates of apoptosis. Maximal apoptosis was noted between 48-96 h. In order to probe the mechanism further we measured the levels of nitrites as an indicator of nitric oxide (NO) in the media. NO levels were significantly elevated at the doses that caused an induction of apoptosis. The results from this study indicate that STE causes a dose-dependent induction of apoptosis and that this is mediated by nitric oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006985700851
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  • 7
    Electronic Resource
    Electronic Resource
    Nitric oxide inhibits wound collagen synthesis (1999)
    Springer
    Molecular and cellular biochemistry 200 (1999), S. 27-33 
    Details
    ISSN: 1573-4919
    Keywords: skin ; wound ; nitric oxide ; collagen ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Nitric oxide (NO) is a messenger molecule which regulates many physiological functions like immunity, vascular tone and serves as a neurotransmitter. Although it is known to participate in healing process, its role in collagen synthesis is not clear. Therefore, the present investigation was done to study the role of NO in wound collagen synthesis. Rats received full thickness, circular (8 mm), transdermal wounds which were treated with NO releaser, sodium nitroprusside (SNP, 0.001 100 μM) topically for 5 days. Wound collagen content estimated in terms of hydroxyproline (HP) and confirmed histochemically was decreased significantly by all SNP doses. L-Arginine, a substrate for nitric oxide synthase (NOS) when applied topically decreased collagen content of the wounded tissues. N-Nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of NOS, increased wound collagen content significantly as compared to untreated and SNP treated animal wounds when administered intraperitoneally at the doses 3, 10 and 30 mg/kg. Furthermore, histological findings also demonstrated laying down of thick collagen bundles and proliferation of fibroblasts together with prominent angiogenesis in L-NAME treated wound tissues as compared to untreated and SNP treated tissues. N-nitro-D-arginine methyl ester, an inactive isomer, was found to have no effect on wound collagen levels. When L-arginine was administered in L-NAME pretreated rats, it significantly elevated wound HP content. The results indicate that NO plays an important role in regulating the collagen biosynthesis in skin model of a healing wound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006977513146
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  • 8
    Electronic Resource
    Electronic Resource
    Myocardial preconditioning: Basic concepts and potential mechanisms (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 3-12 
    Details
    ISSN: 1573-4919
    Keywords: ischemia ; preconditioning ; adenosine ; protein kinase C ; KATP channel ; free radicals ; heat shock proteins ; antioxidants ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Preconditioning is a phenomenon, where brief periods of stress such as ischemia, heat shock or certain pharmacological agents make the heart tolerant to subsequent lethal ischemic injury. Preconditioning seems to involve a variety of stress signals which include activation of membrane receptors and signaling molecules such as protein kinase C, mitogen-activated protein kinases, opening of ATP-sensitive potassium channel and expression of a number of protective proteins. In this review, the potential role of these mechanisms is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006949626070
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  • 9
    Electronic Resource
    Electronic Resource
    Fever: An integrated response of the central nervous system to oxidative stress (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 125-132 
    Details
    ISSN: 1573-4919
    Keywords: fever ; E. coli lipopolysaccharide ; dithiothreitol ; methylene blue ; nitric oxide ; malondialdehyde ; biothiols ; glutamate ; NMDA-receptor ; oxidative stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Immediately after bacterial endotoxin (LPS) enters the circulatory system there is increased production of free oxygen radicals by cells of the reticulo-endothelial system, followed by the release of cytokines considered as putative endogenous pyrogens. Fever originates by central nervous system activities, but neither exogenous nor endogenous pyrogens are able to cross the blood-brain barrier and the true signal which is transmitted to structures inside the blood-brain barrier is still unknown. To study the role of oxygen radicals in fever, we pretreated rats with methylene blue, an inhibitor of superoxide and hydroxyl radical production and investigated the febrile response to LPS in conscious rats by measuring malondialdehyde formation as an index of lipid peroxidation by oxygen radicals. Methylene blue lowered resting malondialdehyde levels to near detection level and significantly suppressed its rise which was regularly found following LPS in the untreated state. Pretreatment with methylene blue completely blocked the febrile response. Since fever is a central nervous system-mediated response these results indicate that the brain is able to sense oxidative stress and vicinal thiol groups of the redox-modulatory site of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor-channel complex could function as a possible receptive structure. To test this hypothesis we injected rabbits with the disulfide reducing agent dithiothreitol (DTT), known to penetrate the blood-brain barrier, and monitored its effect on normal and febrile body temperatures. DTT induced, independently of ambient temperature, within minutes and dose-dependently the full pattern of heat loss responses causing a fall of core temperature, indicative of a lowered thermoregulatory setpoint. Pretreatment with a bolus dose of 5 mg/kg DTT, followed by a continuous infusion of 5 mg/kg/h for 3 h completely prevented LPS-induced fever. A bolus dose of 20 mg/kg DTT, starting 30 min after LPS, immediately reversed the febrile cold defense pattern and lowered body temperature. We conclude that DTT reduces in the central nervous system oxidized vicinal thiol groups of NMDA receptors, thereby augmenting glutamate-induced nitric oxide synthase activation, and, thus, enhanced formation of NO, which, in turn, lowers the thermoregulatory setpoint. Reduction of other disulfide-containing molecules, especially oxidized glutathione and thiol-containing enzymes, by DTT by might additionally contribute to preventing fever.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006936111474
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  • 10
    Electronic Resource
    Electronic Resource
    2-Bromoacetyl-6-methoxynaphthalene: A useful fluorescent labelling reagent for HPLC analysis of carboxylic acids (1992)
    Springer
    Chromatographia 33 (1992), S. 13-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fatty acids and bile acids ; Fluorogenic precolumn derivatization ; 2-Bromoacetyl-6-methoxynaphthalene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 2-bromoacetyl-6-methoxynaphthalene as a fluorogenic labelling reagent in pre-column derivatization for the HPLC separation of biologically active carboxylic acids (fatty acids and bile acids) has been investigated. The compound reacts (30 min. at 70°C) with carboxylic acids to give fluorescent esters that can be separated by reversedphase HPLC and detected at λ ex. 300 nm, λ em. 460 nm. The experimental conditions for the derivatization and chromatographic separation are discussed. Applications to the determination of valproic acid and chenodeoxycholic acid in pharmaceutical formulations are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276844
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  • 11
    Electronic Resource
    Electronic Resource
    HPLC method for the simultaneous analysis of valproic acid and other common anticonvulsant drugs in human plasma or serum (1992)
    Springer
    Chromatographia 33 (1992), S. 37-40 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Valproic acid ; Simultaneous determination of anticonvulsants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The derivatizing procedure of Moody et al. [20] for valproic acid has been simplified and applied to the simultaneous HPLC determination of valproic acid (VPA), barbital (B), primidone (PRM), phenobarbital (PB) and carbamazepine (CBZ) in serum or plasma of epileptic patients. The sample is deproteinized with acetonitrile containing esterification agents and an aliquot of the supernatant is heated to 70°C for 15 min with 4-bromophenacyl bromide. The reaction mixture is analysed on a C18 column at ambient temperature, with gradient elution and with detection at 205 nm. The time required for the chromatographic analysis is 13 min; identification is based on retention time and quantification is by peak area determination with an internal standard. The calibration curves show good linearity in the range 6.25 to 100 mg/L. The detection limits at a signal: noise ratio ≥3, ranged from 1 mg/L for B and CBZ to 2–3 mg/L for PRM, PB and VPA. The method described for the simultaneous determination of the five drugs in the same plasma pool, correlated well with isocratic HPLC methods specific for each drug. The simultaneous procedure described allows a reproducible (CVs≤6.5% within run) and rapid (25 min for sample preparation: 13 min for chromatographic run) therapeutic monitoring of patients treated with VPA and two or more antiepileptic drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276848
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  • 12
    Electronic Resource
    Electronic Resource
    Porous polymer packings from vinyl ether derivatives for reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 19-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous polymer spherical packings ; Vinyl ether ; Alkali resistance ; No abnormal adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Spherical, porous-polymer particles for column packing in high-performance liquid chromatography were prepared by suspension copolymerization of alkylvinyl ether with triethyleneglycol divinyl ether. The hydrophobicity of the packings was easily adjusted by changing the monomer ratio. The packings showed the usual reversed-phase liquid chromatographic properties, but did not sho abnormal retention, tailing and broadening of peaks and irreversible adsorption of ionic and aromatic substances, owing to the lack of ionic or aromatic groups. In addition, the packings were stable in alkaline solutions because of the relative alkali stability of C−O−C bonds as compared with CO−O and Si−O−C bonds in conventional packings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276845
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  • 13
    Electronic Resource
    Electronic Resource
    Comparison study between indirect photometric and direct conductivity detection for anion exchange chromatography using naphthalenesulfonate derivatives as mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 25-31 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange ; Indirect photometric and direct conductivity detection ; Naphthalenesulfonate ; Inorganic anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Indirect photometric and unsuppressed direct conductivity detection modes are examined using naphthalene mono-, di-, and tri-sulfonate as mobile phases for the separation of several anions such as F−, Cl−, NO2 −, Br−, NO3 −, SO4=,I−, and SCN− using a commercial anion exchange column. With all three mobile phases, conductivity detection shows better sensitivities and detection limits than indirect photometry. Conductivity detection is 5 to 16 times more sensitive than indirect photometry for all analytes. Detection limits achieved using these mobile phases are, for example, 0.04 ng and 0.1 ng for chloride ion with conductivity and indirect photometry, respectively. Both detection modes give wide linear ranges extending from at least 100 ppm to the detection limit of each anion which is generally about 0.02 ppm. Sulfur oxide anions such as dithionate and tetrathionate are separated using flow programming with naphthalenetrisulfonate as the mobile phase in less than 20 minutes. With both detection modes, desired chromatographic performance of these three eluents is achieved without pH adjustment of the mobile phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276846
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  • 14
    Electronic Resource
    Electronic Resource
    An enhanced liquid chromatographic method for 5-hydroxymethylfurfural determination in UHT milk (1992)
    Springer
    Chromatographia 33 (1992), S. 45-48 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heat-treated milk ; Milk quality indicators ; 5-Hydroxymethyl-2-furfuraldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An enhanced method of HPLC for the determination of 5-Hydroxymethyl-2-furfuraldehyde (HMF) in fluid milk was perfected. Its resolving capacity permitted the specific separation of this compound. The real concentration (μmol/l) of HMF was determined and not the HMF value, as in the colorimetric analysis, where an intermediary coloured compound (HMF-TBA) is utilised. The optimum pH condition (pH=4.0–4.2) for the mobile phase to prevent overlapping between the HMF peak and the peaks of the other compound (α and β) that coeluted with the HMF and also the optimum organic solvent content (3% or 7%) were established. This is a sensitive, quick and safe method for the determination of HMF in fluid milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276850
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  • 15
    Electronic Resource
    Electronic Resource
    Ion-pair reversed-phase liquid chromatography of arsenic species on polymeric styrene-divinylbenzene packed columns with an alkaline aqueous mobile phase (1992)
    Springer
    Chromatographia 33 (1992), S. 581-585 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Arsenic compounds ; Polymeric styrene divinylbenzene phase ; Ion-pairing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolving power of an ion-pair reversed-phase liquid chromatography method, on a polymeric stationary phase (PRP-1) with an alkaline aqueous mobile phase (pH=9) containing tetrabutylammonium cation as ion-pairing agent, is compared with a traditional ion-pairing system using an octadecyl-modified silica column and a neutral aqueous mobile phase (pH=7.3). This chromatographic system (PRP-1 column) provides a rapid means for the determination of two of the most important arsenic species, arsenobetaine and arsenite. Addition of methanol (5%) to the aqueous mobile phase allows the differentation of arsenobetaine from the system peak when using UV detection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262252
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  • 16
    Electronic Resource
    Electronic Resource
    Comparison of provitamin A determination by normal-phase gravity-flow column chromatography and reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 133-137 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gravity-flow column chromatography ; Provitamin A determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The provitamin A content of some food samples was determined by methods involving MgO: Hyflosupercel gravityflow column chromatography (GFCC) and reversed phase high performance liquid chromatography (HPLC), the quantitation being done by external standardization (HPLC-ES) or internal standardization (HPLC-IS) with Sudan. The results obtained with α- and β-carotene in carrots, β-carotene and β-cryptoxanthin in papaya and β-carotene in tomato and kale agreed well, showing that any of the these techniques can be used, provided the analysis is done under optimum conditions. Good separation of the different provitamins using GFCC depends on the analyst's skill and visual acuity. HPLC-ES required a constant supply of provitamin standards, thus the varying purity of commercially available standards and the high instability of these compounds could pose grave problems. Due to the stability of Sudan, HPLC-IS appeared to be the method of choice although passage of the extract through a MgO: Hyflosupercel minicolumn was required prior to injection to separate chlorophylls, dihydroxy- and polyoxycarotenoids which would otherwise elute with Sudan. Nonconformity of the Sudan structure to those of the provitamins did not effect the quantitative results. The chromatographic separation, identity and quantification of the provitamins could be more easily established by using HPLC-IS, complemented with GFCC.
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    URL: http://dx.doi.org/10.1007/BF02275893
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  • 17
    Electronic Resource
    Electronic Resource
    Diastereoselective and enantioselective chromatography of the pyrethroid insecticides allethrin and cypermethrin (1992)
    Springer
    Chromatographia 33 (1992), S. 103-112 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275888
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  • 18
    Electronic Resource
    Electronic Resource
    Estimation of diuretic drugs in biological fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 177-185 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diuretics ; Screening and determination of diuretics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275902
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  • 19
    Electronic Resource
    Electronic Resource
    Peak recognition technique by a computer program copying the human judgement (1992)
    Springer
    Chromatographia 33 (1992), S. 218-224 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Peak ; Pattern recognition ; Prediction interval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is still difficult to determine peaks and peak boundaries properly, though peak recognition is very important for the precision of quantitative data. A new computer program overcomes these problems using a method which is adapted from human judgements. The algorithm was developed for HPLC but can also be used in other fields of analytical chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276186
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  • 20
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    High performance liquid chromatography of raw sugars and polyols using bonded silica gels (1992)
    Springer
    Chromatographia 33 (1992), S. 325-330 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diol silica gels ; Carbohydrates ; Evaporative light scattering detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bonded silica columns have been evaluated for their ability to separate carbohydrates and polyols. Mobile phases consisting of dichloromethane/methanol produced the best separations in comparison with the acetonitrile/water mixtures commonly used with amino columns. Of all the bonded phases tested, LiChrospher Diol silica provided the best separations, and selectivities were not very different from those obtained on the most popular system using an amino bonded phase and acetonitrile/water as eluent. In addition, diol columns with a dichloromethane/methanol eluent offer excellent stability with no Schiff’s base formation of reducing sugars. Using an evaporative light scattering detector, low limit detection is obtainable (20 ng of glucose from a column) and gradient elution is quite feasible.
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    URL: http://dx.doi.org/10.1007/BF02275911
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    Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters (1992)
    Springer
    Chromatographia 33 (1992), S. 356-360 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitized carbon ; Ring-substituted aniline derivatives ; Electronic interactions ; Principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention characteristics of 22 aniline derivatives were determined on a porous, graphitized-carbon column in unbuffered acetonitrile-water and methanol-water mixtures. Each aniline derivative gave symmetrical peaks in each eluent without buffers. Good linear correlations were found between the log k′ and the concentration of the organic component in the eluent. The slope and intercept values differed according to the type of organic modifier and the charcter, number and position of substituents, indicating the different selectivities of methanol and acetonitrile and the good separating power of the column. Multivariate mathematical-statistical calculations proved that the retention of ring-substituted aniline derivatives is mainly governed by electronic parameters and the hydrogen acceptor capacity of substituents.
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    URL: http://dx.doi.org/10.1007/BF02275918
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    Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 374-376 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pairing ; Furosine ; Pyridosine ; Milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r〉0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.
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    URL: http://dx.doi.org/10.1007/BF02275921
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    Optimisation of data handling and detection conditions for automated chromatographic assay software (1992)
    Springer
    Chromatographia 33 (1992), S. 361-368 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Automated peak detection ; Discrete Fourier transform ; Frequency acquisition and filtering ; Peak detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The principle of automated chromatographic peak detection and analysis software is summarized, and critical steps are systematically studied. As the only parameter to be entered is the acquisition frequency, evaluation of its effect on software performance is discussed. In the case of relatively noisy chromatograms, it is shown experimentally that numerous points per peak have to be taken, leading to quite fast computer acquisition procedures. The use of discrete Fourier transform filtration techniques can modify peak shapes and a comparative study evaluates the relative errors induced in the shapes and characteristics of the chromatographic profiles. Optimisation of filtering conditions is achieved and it is shown that for a filter position only 2% of the Nyquist frequency no deformation occurs in the chromatographic profile. Detection of the start and finish of chromatographic peaks is optimized according to a simple four step iterative procedure. In the case of simulations, the difference between the values used to simulate peaks and those calculated by the software are less than 1%.
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    URL: http://dx.doi.org/10.1007/BF02275919
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    Simultaneous determination of 5′-deoxy-5-fluorouridine, 5-fluorouracil and its main metabolites in body fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 413-417 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluoropyrimidine drugs ; Pharmacokinetics of doxifluridine ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase high performance liquid chromatographic method has been developed for the simultaneous determination of the pro-drug 5′-deoxy-5-fluorouridine (5′-dFUR), its metabolite 5-fluorouracil (5-FU) and some fluorinated pyrimidines involved in the metabolic activation process of 5-FU. The method has been used to monitor the bioavailability of 5′-dFUR and 5-FU in patients undergoing anticancer chemotherapy. Serum sample treatment involves addition of internal standard (5-bromouracil), protein precipitation with saturated ammonium sulphate solution and liquid-liquid extraction with ethyl acetate-isopropanol (90 ∶ 10 v/v). Urine is simply diluted with mobile phase and injected. The average recovery from serum (at 0.5 μg/mL level) was 95.0%±1.4 for 5′-dFUR and 86.3%±3.5 for 5-FU. A linear response extending over four decades of concentration was observed. Detection limits in the low ng/ mL range were obtained using a 250 μL sample size and a 20 μL injection volume. Within-day and between-day coefficients of variation were below 4 and 10%, respectively.
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    URL: http://dx.doi.org/10.1007/BF02262320
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    Total and individual determination of carbamate pesticides by use of an integrated flow-injection/HPLC system (1992)
    Springer
    Chromatographia 33 (1992), S. 449-453 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined flow injection/HPLC ; Carbamate pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An integrated flow injection (FI)/HPLC system for the total and individual determination of carbamate pesticides (propoxur, carbofuran and carbaryl) is proposed. The determination is based on the alkaline hydrolysis of the analytes and subsequent coupling with diazotized sulphanilic acid to yield the monitored dyes with or without a prior separation step by HPLC in a C18 column. The calibration curves obtained are linear in the μg/ml range and r.s.d. values are between 0.5 and 3.7% in all instances. Injection of the sample into the FI manifold allows the total pesticide content in the sample to be screened. The manifold thus acts as a post-column reactor/detector of the chromatograph for samples with high overall carbamate content, which are also injected into the HPLC instrument. The performance was checked with contaminated water samples.
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    URL: http://dx.doi.org/10.1007/BF02262326
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    Evaluation of the enantioselectivity towards β-blocking agents of the α1 glycoprotein type chiral stationary phase: Chiral AGP®glycoprotein type chiral stationary phase: Chiral AGP® (1992)
    Springer
    Chromatographia 33 (1992), S. 454-462 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantioselectivity of the α1 glycoprotein chiral stationary phase, Chiral AGP® has been evaluated for a number of β-blocking agents. A correlation has been found between the retention behaviour on this stationary phase and the hydrophobicity of the compounds. The separation factor α is higher for compounds that are well retained. Retention, and thus α, are also controlled by pH and the percentage of organic modifier in the mobile phase.
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    Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings (1992)
    Springer
    Chromatographia 33 (1992), S. 473-477 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Perfluoroalkylated polymer-gel packings ; Aromatic and fluorine-containing compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Porous, perfluoroalkylated polymer-gels for column packings in high-performance liquid chromatography (HPLC) were prepared by suspension polymerization of heptadecafluorodecyl arcylate and ethylene glycol dimethacrylate. The packings showed no abnormal retention for ionic or aromatic compounds, due to the lack of ionic or aromatic groups. In addition, the packings showed no excessive retention for strongly hydrophobic compounds which is often the case with long-chain, alkylated silica gels and polymer gels. This is due to the extremely low surface energy of perfluoroalkyl groups. Therefore, perfluoroalkylated polymer gels enable isocratic HPLC separation of solutes with significantly different hydrophobicity.
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    URL: http://dx.doi.org/10.1007/BF02262330
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    Comments on the paper “correlation between retention in liquid chromatography and the adsorption energy” by J. Kloubek (1992)
    Springer
    Chromatographia 33 (1992), S. 485-486 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1007/BF02262332
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    Correlation between retention in liquid chromatography and the adsorption energy (1992)
    Springer
    Chromatographia 33 (1992), S. 478-484 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass adsorbents ; Surface free energy ; Oriented adsorption of hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the specific capacity factor (k/S, where k is the capacity and S is the surface area of the sorbent, in m2) in the liquid chromatography of aromatic hydrocarbons and the adsorption energy (-°GA) has been investigated. The previously published results, based on the calculation of the work of adhesion (WSA) from contact angles, were re-examined and a new hypothesis on interactions at interfaces was employed. Direct proportionality has been found between k/S and-°GA, which allows prediction of the chromatographic behavior of adsorbates on sorbents. The surface free energy components were calculated in order to determine-°GA in terms of the work of adhesion. The dispersion component of the surface free energy of glass was obtained from the adsorption isotherm of n-octane and it was found that the hydrocarbon molecules are adsorbed in an oriented position. The contact angles of liquids on the outer surface of porous solids do not yield reliable values of WSA and of the surface free energy components. A higher intermolecular attraction increases WSA and decreases the contact angle in pores.
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    A high-performance liquid chromatographic method for the analysis of adenosine and some metabolites in the brain tissue of rats (1992)
    Springer
    Chromatographia 34 (1992), S. 563-567 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine and some metabolites ; Extraction from brain tissue ; Quantitative determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the assay of adenosine and some metabolites in brain tissue extracts of rats. This paper reports the extraction method, the technique adopted to avoid enzymatic transformations and the chromatographic conditions for the identification and quantitation of these nucleosides and bases. Peaks in the chromatograms of brain tissue extracts were identified by retention times, absorbance ratios of reference compounds and by enzymatic peak-shift.
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    Influence of silica gel surface purity on the coverage density of chemically bonded phases (1992)
    Springer
    Chromatographia 34 (1992), S. 573-580 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases (CBP) ; Surface heterogenity ; Surface purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The surface chemistry of eight silica-gels with different siliceous matrix structures have been described. The influence of surface impurities on the chemical modification process (coverage density) with monooctadecylsilane has been studied. The surfaces of the adsorbents, before chemical modification, were cleaned by extraction with 20% HCl. Bare and modified materials were characterized using different physico-chemical methods e.g.: SIMS, CP/MAS NMR, porosimetry, pH measurement, elemental analysis and chromatography (GC & HPLC). The presence of trace amounts of different metallic elements creating new adsorption centers on the surfaces of the packings, have been demonstrated. Moreover, it has been shown that washing of silica gel adsorbents increases the coverage density of alkylsilyl ligands and improves the chromatographic properties of prepared packings.
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    Zone electrophoretic sample treatment coupled on-line with column liquid chromatography for the determination of basic and acidic compounds in biological samples (1992)
    Springer
    Chromatographia 34 (1992), S. 581-588 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified valve arrangement for zone-electrophoretic sample treatment (ZEST)-which is coupled on-line with column liquid chromatography — is used to pretreat biological (plasma) samples. Carry-over of plasma proteins depends on the pH of the electrophoresis buffer. The determination of propranolol, metoprolol, cromolyn and salicylic acid demonstrates that both basic and acidic analytes can be isolated from the plasma matrix with high selectivity. Analogous piperazines, with different protein binding properties, were used to study the influence of protein binding on the recovery. It is shown that high protein can cause a decreased recovery.
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    HPLC analysis of the main oxindole alkaloids fromUncaria tomentosa (1992)
    Springer
    Chromatographia 34 (1992), S. 597-600 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxindole alkaloids ; Uncaria tomentosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The main oxindole alkaloids from the root bark ofUncaria tomentosa were separated by reversed phase HPLC with an acetonitrile/methanol/phosphate buffer solvent gradient. UV detection was carried out at 245 nm. The chromatographic parameters for the separation of the alkaloids were optimized by studying the impact of the pH value of the mobile phase and the column temperature on the separation efficiency of the analytical system. The best separation was achieved with a mobile phase pH of 6.6 and a column temperature of 15°C. The method developed is suitable for the qualitative characterisation and quantitative determination of oxindole alkaloids in crudeUncaria tomentosa extracts and phytopharmaceuticals.
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    Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 618-620 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomers of furprofen ; Human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and stereoselective liquid chromatographic (HPLC) assay for the S and R enantiomers of furprofen in human plasma has been developed. The assay is based on derivatization with S(−)-1-phenylethylamine with formation of two diastereoisomeric derivatives and on their separation and quantitation using HPLC with uv detection. The method is linear from 25 to 600 ng ml−1 of both enantiomers, with a variation coefficient below 10.8%, and a detection limit of 20 ng ml−1. This procedure is suitable for pharmacokinetic studies.
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    Solute-micelle association constants and correlation of octanol-water coefficients with hydrophobicity for polycyclic aromatic hydrocarbons by micellar chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 627-635 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micelle-solute association constants ; Polynuclear aromatic hydrocarbons ; Octanol/water partition coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sodium dodecyl sulphate, hexadecyltrimethylammonium bromide and polyoxyethylene(23) lauryl ether were investigated as mobile phases in the micellar liquid chromatography of polycyclic aromatic hydrocarbons of environmental concern. A wide range of surfactant concentrations were used and the retention parameters and distribution coefficients calculated. The trends in the retention data for the PAHs are discussed and several conclusions are presented concerning the partition coefficients when these surfactants are present in the mobile phase. Comparisons are made between the structural features of the compounds and their capacity factors, and the octanol/water partition coefficients are correlated with hydrophobicity for the PAHs studied.
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    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs (1992)
    Springer
    Chromatographia 34 (1992), S. 115-120 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
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    A column switching technique for the determination of lidocaine and its metabolites in horse urine (1992)
    Springer
    Chromatographia 34 (1992), S. 143-145 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method is described for the determination of lidocaine and its metabolites in horse urine using a column switching technique and HPLC analysis. This procedure offers a sensitive assay without the need for time consuming extractions.
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    URL: http://dx.doi.org/10.1007/BF02276127
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    Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates (1992)
    Springer
    Chromatographia 34 (1992), S. 132-136 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cysteine, cystine ; Phenylthiocarbamyl derivatives ; Protein hydrolyzates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new approach is described, and a novel explanation presented, for the high performance liquid chromatographic analysis of cystine and cysteine as their phenylthiocarbamyl derivatives. PTC cystine and cysteine have been eluted with the same retention times and molar responses, most probably due to electrophilic attack of phenylisothiocyanate on cystine resulting in the scission of the disulfide bond yielding two moles of cysteine. Further, total PTC cystine and cysteine have been measured both in model solutions and in standard protein hydrolyzates (lysozyme, bovine albumin, ribonuclease) with the same linearity as the other ineteen amino acids. The reproducibility of the measurements, at the 250–750 pmole level, proved to be 4.1% (Relative Standard Deviation %) or less.
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    Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 155-158 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na+] and not on [K+] at concentrations of K+ from 5×10−7 to 10−1 mol l−1. Hence, actinomycin D may be classified as an ionophore-antibiotic.
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    Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns (1992)
    Springer
    Chromatographia 34 (1992), S. 146-154 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isocratic column liquid chromatographic systems with UV absorbance detection at 280 nm have been developed for the separation of 29 phenolics and related compounds. The selectivity was investigated on silica-, carbon- and polymer-based separation columns for the separation of phenolic type of components. The effects of various acetonitrile/buffer mixtures, and pH of the mobile phase, and their impact on the retention of the phenols was assessed. Tables of retention times on the four columns for the 29 phenols with two different acetonitrile/buffer mixtures, together with the retention times at three pHs from 6.5 to 2.3 with varying levels of organic modifier on the LiChrospher RP 18 column are presented. As an application, the analysis of real river water samples from the Ebro river is described using a solid phase extraction step prior to injection into the chromatographic system.
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    Microcolumn liquid chromatography on carbon sorbents (1992)
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    Chromatographia 34 (1992), S. 173-176 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention volume dependences on the molar volume were found for aromatic compounds using liquid microcolumn chromatography. The contributions of the functional groups in molecules of these compounds to the total retention value were calculated from the capacity factor values. The comparison of capacity factor values for carbon sorbents and octadecyl-silicagel has shown that for several microcolumn separations the carbon sorbent column has a better selectivity and resolution than the octadecyl-silicagel column.
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    Synthesis of acceptor bonded phases for donor-acceptor liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 177-181 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of several electron-acceptor stationary phases has been reviewed the materials evaluated for their capacity to separate polyaromatic hydrocarbons (PAHs). Chemically bonded phases were obtained by the same procedure; the organosilane moiety is monofunctional and the HPLC behaviour is compared under identical conditions. Examples of PAHs separations are given.
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    Silanol group effect in C18 bonded phases in HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 182-184 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary If any residual (free) silanol groups remain at the surface of silica gel after bonding treatment, they may affect the retention of solutes since the dissociated groups (≡SiO−) will attract cations. The silanol group effect on the retention of cationic solutes will increase with increasing pH of the mobile phase but the effect will decrease with increasing hydrophobic-ion concentration at the C18 surface because such ions can mask the residual silanol groups. A method for the separation of metal complexes with 2-(5-bromo-2-pyridylazo)-diethylaminephenol (5-Br-PADAP) has been developed. The hydrophobic ion in the MeOH/H2O mobile phase was tetrabutylammonium (TBA).
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    Michael Tswett's columns: Facts and speculations (1992)
    Springer
    Chromatographia 34 (1992), S. 342-346 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Although Michael Tswett is the originator of chromatography, little is known about the performance of his chromatographic systems. His descriptions of the separation of plant pigments are detailed but nevertheless difficult to interprete by today's chromatographic theory. By our own experiments with the system calcium carbonate/benzene it was found that the separation factor of chlorophyll a and b is approx. 1.6 which means that less than 100 theoretical plates are necessary for separation. Tswett's columns with 50 μm particles and 2–3 cm of bed height presumably exceeded this plate number. His separations could have been impaired by mass overload and by a volume flow rate which was two orders of magnitude faster than the optimum.
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    Factors influencing retention and resolution of substituted alkylbenzenes in reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 347-356 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention data of isomeric xylenes, ethyltoluenes and diethylbenzenes, and of mesitylene, benzene, toluene and ethylbenzene were obtained on a reversedphase column using methanol-water and ethanol-water mobile phases at four different temperatures. This database was used to relate the dependence of solute retention and resolution on the polarity of the mobile phase, solute dipole moment, and column temperature. The additivity of the free energy of the transfer of solute molecules or solute segments from the stationary phase to the mobile phase, was examined for the isomeric compounds. For this, the logarithm of the net retention volume was substituted for the free energy. Deviations from the additivity of free energies indicate that the separation of isomeric substituted alkylbenzenes is governed by their differential interactions with both the polar mobile phase and nonpolar stationary phase. Among the disubstituted alkylbenzenes,ortho-isomers favor the mobile phase more andpara-isomers tend to prefer the stationary phase more. Themeta-isomers are found to follow the additivity rule closely. These trends are amplified as the polarity of the mobile phase is increased indicating that these isomers are resolved better in water-rich mobile phases. These findings are substantiated by analogous results from gas-liquid chromatographic retention data, estimation of dipole moment effects, and examination of the entropic and enthalpic contributions to the net retention volume.
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    Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching (1992)
    Springer
    Chromatographia 34 (1992), S. 376-380 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.
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    URL: http://dx.doi.org/10.1007/BF02268371
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    Gradient high performance liquid chromatography of block copolymers of styrene andt-butyl methacrylate II. Association phenomena in mixtures of block copolymer with polystyrene (1992)
    Springer
    Chromatographia 34 (1992), S. 363-368 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Block copolymers of styrene andt-butyl methacrylate can be analysed by methanol/tetrahydrofuran gradients on C18 or phenyl bonded phase columns. On both of these columns, retention increases with styrene content of the samples. At 50°C, the retention of PS or a block copolymer containing 45% styrene was longer on the phenyl than the C18 columns. This indicates the contribution of adsorption to retention on phenyl bonded phase columns. Lowering the temperature from 50 to 30°C caused earlier elution of part of the sample from the phenyl phase. On a C18 phase the same drop in temperature improved the shape of the peak, which also started later than at 50°C. This effect of temperature is generally observed in polymer retention due to an adsorption mechanism, whereas increasing retention with decrease in temperature is characteristic of a precipitation mechanism. The block copolymer investigated contained 15% free polystyrene precursor which could not be separated from the block copolymer under the conditions employed. The addition of 20% PS homopolymer with a molecular weight similar to that of the styrene block in the copolymer showed that the polystyrene eluted together with the block copolymer, whereas the addition of PS homopolymer with a much higher molecular weight caused an extra peak at the expected elution time.
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    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary New multidentate phenyl-bonded phases (MPBPs) were synthesized and evaluated the chromatographic retention behaviour with polycyclic aromatic hydrocarbons as sample probes in high-performance liquid chromatography. The new MPBPs show different retention characteristics from the previously synthesized MPBP, designated TP. Nevertheless, the results indicate that the retention mechanism is still the same as the TP phase: the size and shape of the solute molecule can be recognized by a cavity-like space formed by the methyl groups and phenyl rings of MPBPs.
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    Comparison and evaluation of HIC columns of different hydrophobicity (1992)
    Springer
    Chromatographia 34 (1992), S. 391-397 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log kw values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (kg) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.
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    Chromatographic characteristics of porphyrine ether glycerides (1992)
    Springer
    Chromatographia 34 (1992), S. 431-432 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Efficient TLC and HPLC conditions for the separation of a newly synthesized class of compounds, porphyrine ether glycerides, have been established. Supplementary physico-chemical characteristics are given for this group of solutes.
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    Integrated FIA/HPLC method for preconcentration and determination of transition metal ions (1992)
    Springer
    Chromatographia 34 (1992), S. 445-449 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automatic method based on the combination of a flow injection (FI) manifold with a liquid chromatograph has been developed for the enrichment and determination of transition metal ions in water samples. Alternatively, the FI configuration can be used as a screening system for the determination of the total concentration of heavy metals. Two-parameter expressions for calibration graphs involving preconcentration time and concentration of the analytes were established for both the FIA and the integrated FIA/HPLC methods. The preconcentration time depends on the concentration level of the analytes in the samples. The method is linear in the range 2–200 ng/ml, with r.s.d. values between 1.5 and 5.0. It has been applied to the determination of copper, lead, zinc, nickel, cobalt, cadmium and manganese in synthetic water samples.
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    Comparison of HPLC and solid phase clean-up methods for identification of PCBs in cod-liver oil by HRGC/MS-SIM technique (1992)
    Springer
    Chromatographia 34 (1992), S. 421-430 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A group of non-planar PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) was identified in a cod-liver oil product by using high resolution gas chromatography-mass spectrometry (HRGC/MS) in electron impact (EI) and negative chemical ionization (NCI) modes. The cod-liver oil samples were prepared either in a cyano column by high performance liquid chromatography (HPLC) or by a solid phase extraction (SPE) clean-up procedure that included e.g. purified charcoal treatment. The two methods of sample preparation were evaluated on the basis of the detectabilities of the congeners. The GC/MS-SIM method allowed quantitative monitoring of congeners nos. 52, 101, 118, 138, 153, and 180 at low concentration levels. Detection limits were 1.2 pg and 130 fg (m/z 292.00) in EI and NCI modes, respectively. The determination levels in EI and NCI were 1.8 pg and 290 fg in HPLC followed by HRGC/MS and 170 pg and 27 pg in SPE followed by HRGC/MS. The linear range was from 5.0 pg/μl to 1.0 ng/μl and from 1.0 pg/μl to 1.0 ng/μl in EI and NCI modes, respectively. In addition, the co-planar PCBs, PCDDs, and PCDFs were also screened and two of the chlorinated furanes were identified by HRGC/MS-NCI after separation from non-planar PCBs by SPE. In this case the only congeners that could be quantified were 2,3,4,7,8-PCDF and 1,2,3,4,6,7,8-HCDF, the detection limit for them being 740 fg (m/z 351.90) with NCI. SPE allows the separation of the planar and non-planar compounds, but LC separation is more effective for separation of the compounds of interest from the matrix. LC clean-up is easier and faster to perform than SPE clean-up.
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    Separation of stereoisomers of tetramethylcalix[4]arenoctol and derivatives by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 453-456 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatographic procedure on 5 μm RP-18 was developed for the separation of the four possible cis-trans isomers of tetramethyl-calix[4]arenoctol, and of their octaacetates, and their octamethyl ethers.
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    HPLC separation of molecular species of intact sphingomyelin, utilizing multivariate design and optimization (1992)
    Springer
    Chromatographia 34 (1992), S. 529-533 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved method has been developed for the separation of molecular species of intact sphingomyelins from natural sources (chicken egg yolk, bovine brain, and bovine milk) by high performance liquid chromatography with light-scattering detection. The method was developed and optimized using a novel multivariate optimization strategy.
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    High-performance liquid chromatography of carbohydrates in enzymic hydrolysate of waste paper (1992)
    Springer
    Chromatographia 34 (1992), S. 534-536 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Waste paper was pretreated with 5M sulfuric acid at 28°C to give a gel-like solution which was then hydrolyzed with cellulase, purified fromTrichoderma viride, to form carbohydrates. The determination of the carbohydrates was accomplished using an aminopropylbonded silica HPLC column and an RI detector. The detection limits were 20 ppm; xylose, glucose, and cellobiose were the major components. Salts from the buffer solution may affect the activity of cellulase. The analysis of carbohydrates can be performed under acid conditions. HPLC analysis of carbohydrates from enzymatic hydrolysis is reliable and successful.
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    Nitric Oxide: A Unique Endogenous Signaling Molecule in Vascular Biology (1999)
    Springer
    Bioscience reports 19 (1999), S. 51-71 
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    ISSN: 1573-4935
    Keywords: Cell signaling ; nitric oxide ; vasculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The properties of nitric oxide as an endogenous cell signaling molecule in vascular biology are described.
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    URL: http://dx.doi.org/10.1023/A:1020150124721
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    Discovery of Some of the Biological Effects of Nitric Oxide and its Role in Cell Signaling (1999)
    Springer
    Bioscience reports 19 (1999), S. 133-154 
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    ISSN: 1573-4935
    Keywords: Cell signalling ; nitric oxide ; vasculature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The role of nitric oxide in cellular signaling in the past 22 years has become one of the most rapidly growing areas in biology with more than 20,000 publications to date. Nitric oxide is a gas and free radical with an unshared electron that can regulate an ever-growing list of biological processes. In many instances nitric oxide mediates its biological effects by activating guanylyl cyclase and increasing cyclic GMP synthesis from GTP. However, the list of effects of nitric oxide that are independent of cyclic GMP is also growing at a rapid rate. For example, nitric oxide can interact with transition metals such as iron, thiol groups, other free radicals, oxygen, superoxide anion, unsaturated fatty acids and other molecules. Some of these reactions result in the oxidation of nitric oxide to nitrite and nitrate to terminate its effect, while other reactions can lead to altered protein structure, function, and/or catalytic capacity. These diverse effects of nitric oxide that are either cyclic GMP dependent or independent can alter and regulate important physiological and biochemical events in cell regulation and function. Nitric oxide can function as an intracellular messenger, an autacoid, a paracrine substance, a neurotransmitter, or as a hormone that can be carried to distant sites for effects. Thus, it is a unique simple molecule with an array of signaling functions. However, as with any messenger molecule, there can be too little or too much of the substance and pathological events result. Some of the methods to regulate either nitric oxide formation, metabolism, or function have been in clinical use for more than a century as with the use of organic nitrates and nitroglycerin in angina pectoris that was initiated in the 1870's. Current and future research with nitric oxide and cyclic GMP will undoubtedly expand the clinicians' therapeutic armamentarium to manage a number of important diseases by perturbing nitric oxide and cyclic GMP formation and metabolism. Such promise and expectations have obviously fueled the interests in these signaling molecules for a growing list of potential therapeutic applications.
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    Endothelium-Derived Relaxing Factor: Discovery, Early Studies, and Identification as Nitric Oxide (1999)
    Springer
    Bioscience reports 19 (1999), S. 235-251 
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    ISSN: 1573-4935
    Keywords: Endothelium derived relaxing factor (EDRF) ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The discovery, early studies and identification of endothelium-derived relaxing factor (EDRF) as nitric oxide, are described.
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    A hypothesis for the local control of osteoclast function by Ca2+, nitric oxide and free radicals (1992)
    Springer
    Bioscience reports 12 (1992), S. 369-380 
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    ISSN: 1573-4935
    Keywords: osteoclast ; Ca2+ receptor ; peroxide ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Several important conclusions have recently emerged fromin vitro studies on the resorptive cell of bone, the osteoclast. First, it has been established that osteoclast function is modulated locally, by changes in the local concentration of Ca2+ caused by hydroxyapatite dissolution. It is thought that activation by Ca2+ of a surface membrane Ca2+ receptor mediates these effects, hence providing a feedback control. Second, a number of molecules produced locally by the endothelial cell, with which the osteoclast is in intimate contact, have been found to affect bone resorption profoundly. For instance, the autocoid nitric oxide strongly inhibits bone resorption. Finally, reactive oxygen species have been found to aid bone resorption and enhance osteoclastic activity directly. Here, we will attempt to integrate these control mechanisms into a unified hypothesis for the local control of bone resorption.
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
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    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soilwater and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    Contemporary and pre-industrial global reactive nitrogen budgets (1999)
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    Biogeochemistry 46 (1999), S. 7-43 
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    ISSN: 1573-515X
    Keywords: ammonia emissions ; global nitrogen cycle ; nitric oxide ; nitrogen deposition ; nitrogen pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Increases and expansion of anthropogenic emissions of both oxidized nitrogen compounds, NOx, and a reduced nitrogen compound, NH3, have driven an increase in nitrogen deposition. We estimate global NOx and NH3 emissions and use a model of the global troposphere, MOGUNTIA, to examine the pre-industrial and contemporary quantities and spatial patterns of wet and dry NOy and NHx deposition. Pre-industrial wet plus dry NOx and NHx deposition was greatest for tropical ecosystems, related to soil emissions, biomass burning and lightning emissions. Contemporary NOy + NHx wet and dry deposition onto Northern Hemisphere (NH) temperate ecosystems averages more than four times that of pre-industrial N deposition and far exceeds contemporary tropical N deposition. All temperate and tropical biomes receive more N via deposition today than pre-industrially. Comparison of contemporary wet deposition model estimates to measurements of wet deposition reveal that modeled and measured wet deposition for both NO− 3 and NH+ 4 were quite similar over the U.S. Over Western Europe, the model tended to underestimate wet deposition of NO− 3 and NH+ 4 but bulk deposition measurements were comparable to modeled total deposition. For the U.S. and Western Europe, we also estimated N emission and deposition budgets. In the U.S., estimated emissions exceed interpolated total deposition by 3--6 Tg N, suggesting that substantial N is transported offshore and/or the remote and rural location of the sites may fail to capture the deposition of urban emissions. In Europe, by contrast, interpolated total N deposition balances estimated emissions within the uncertainty of each.
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    The Nitric Oxide Donor SIN-1 Is Free of Tolerance and Maintains Its Cyclic GMP Stimulatory Potency in Nitrate-Tolerant LLC-PK1 Cells (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 633-636 
    Details
    ISSN: 1573-904X
    Keywords: nitrate tolerance ; nitric oxide ; cyclic GMP ; SIN-1 ; molsidomine ; glyceryl trinitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Using an established cell culture model, the present study investigates whether linsidomine (SIN-1), a spontaneous donor of nitric oxide and active metabolite of the antianginal drug molsidomine, induces tolerance to its own cyclic GMP stimulatory action or shows a diminished response after tolerance induction with glyceryl trinitrate. Methods. Incubations with nitric oxide donors were carried out in LLC-PK1, kidney epithelial cells. Intracellular levels of cyclic GMP, the vasodilatory second messenger of nitric oxide, were determined by radioimmunoassay. Results. A 5-h preincubation with glyceryl trinitrate (0.01−100 μM) led to complete inhibition of a subsequent cyclic GMP stimulation by glyceryl trinitrate but left the cyclic GMP response to SIN-1 unaltered. Similarly, cyclic GMP elevations by the spontaneous nitric oxide donors sodium nitroprusside and spermine NONOate were not affected after pretreatment with glyceryl trinitrate. Moreover, pretreatment with SIN-1 (1−1000 μM) had no significant effect on SIN-1-dependent cyclic GMP stimulation. Conclusions. Our results show that in LLC-PK1, cells, SIN-1 is free of tolerance induction and not cross-tolerant to glyceryl trinitrate. This may be due to the spontaneous nitric oxide release from SIN-1, which in contrast to nitric acid esters does not require enzymatic bioactivation and may therefore be unaffected by nitrate tolerance.
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    NO Donor and Biological Properties of Different Benzofuroxans1 (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 956-960 
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    ISSN: 1573-904X
    Keywords: nitric oxide ; NO ; benzofuroxans ; NO donors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the effect of benzofusion on NO donor properties and related biological activities of the furoxan system. The biological properties considered were the ability to increase the cytosolic levels of cGMP in C6 cells and vasodilation. Methods. NO donor properties were investigated either in the presence or the absence of cysteine by using the Griess reaction, chemiluminescence, and gas chromatography. Increase of cytosolic cGMP levels were evaluated by radioimmunoassay. Vasodilating activity was assessed on rat aorta strips precontracted with noradrenaline, in the presence and the absence of oxyhemoglobin (HbO2) and methylene blue (MB), respectively. Results. Benzofuroxan and its methyl and cyano derivatives were unable to release NO under the experimental conditions. Generally these compounds displayed feeble vasodilating properties and were able to weakly stimulate soluble guanylate cyclase (sGC). By contrast, benzodifuroxan and benzotrifuroxan were able to produce both NO• and its reduced form NO−, the nitroxyl anion. They displayed potent vasodilating properties and were able to increase cytosolic levels of cGMP in a concentration-dependent manner. Conclusions. The simple benzofuroxans considered here are devoid of the capability to release NO, they weakly stimulate sGC as well as manifest feeble vasodilating properties by a mechanism that does not involve a thiol-induced NO production. By contrast, benzodifuroxan and benzotrifuroxan behave as typical NO donor furoxans.
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    Contemporary and pre-industrial global reactive nitrogen budgets (1999)
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    Biogeochemistry 46 (1999), S. 7-43 
    Details
    ISSN: 1573-515X
    Keywords: ammonia emissions ; global nitrogen cycle ; nitric oxide ; nitrogen deposition ; nitrogen pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Increases and expansion of anthropogenic emissions of both oxidized nitrogen compounds, NOx, and a reduced nitrogen compound, NH3, have driven an increase in nitrogen deposition. We estimate global NOx and NH3 emissions and use a model of the global troposphere, MOGUNTIA, to examine the pre-industrial and contemporary quantities and spatial patterns of wet and dry NOy and NHx deposition. Pre-industrial wet plus dry NOx and NHx deposition was greatest for tropical ecosystems, related to soil emissions, biomass burning and lightning emissions. Contemporary NOy+NHx wet and dry deposition onto Northern Hemisphere (NH) temperate ecosystems averages more than four times that of preindustrial N deposition and far exceeds contemporary tropical N deposition. All temperate and tropical biomes receive more N via deposition today than pre-industrially. Comparison of contemporary wet deposition model estimates to measurements of wet deposition reveal that modeled and measured wet deposition for both NO 3 − and NH 4 + were quite similar over the U.S. Over Western Europe, the model tended to underestimate wet deposition of NO 3 − and NH 4 + but bulk deposition measurements were comparable to modeled total deposition. For the U.S. and Western Europe, we also estimated N emission and deposition budgets. In the U.S., estimated emissions exceed interpolated total deposition by 3-6 Tg N, suggesting that substantial N is transported offshore and/or the remote and rural location of the sites may fail to capture the deposition of urban emissions. In Europe, by contrast, interpolated total N deposition balances estimated emissions within the uncertainty of each.
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    URL: http://dx.doi.org/10.1007/BF01007572
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soil-water and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    URL: http://dx.doi.org/10.1023/A:1006152112852
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    HPLC separation of catecholamines after derivatization with 9-fluorenylmethyl chloroformate (1992)
    Springer
    Chromatographia 33 (1992), S. 83-86 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-derivatization ; Catecholamines ; 9-fluorenylmethyl chloroformate (FMOC-Cl)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optimum conditions for the separation of 9-fluorenylmethyl chloroformate derivatized catecholamines by HPLC are described; three catecholamines (noradrenaline, adrenaline and dopamine) and an internal standard (epinine) were separated in less than 20 minutes under isocratic conditions. This method is 17 to 350 times more sensitive than electrochemical detection, depending on the test compounds. It has been applied to the analysis of catecholamines in urine. The sample was extracted by a metal-loaded silica prior to separation.
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    URL: http://dx.doi.org/10.1007/BF02276857
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    Preparation and determination of manganese(III) chlorophylls by reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 567-570 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorophylls ; Manganese(III) chlorophylls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Manganese chlorophylls have been synthesized by refluxing a mixture of pheophytins dissolved in acetone and manganese(II) acetate anhydride dissolved in glacial acetic acid. A good separation of manganese(III) chlorophylls has been attained by RP-HPLC using chemically bonded C18 silica as a stationary phase and methanol with 3% acetic acid as a mobile phase. An accurate and rapid HPLC method is described for the simultaneous determination of manganese(III) chlorophyll-a [Mn(III)-chl-a] and manganese(III) chlorophyll-b [Mn(III)-chl-b]. Tailing arising from dissociation of acetate ions is improved by addition of sodium acetate (5×10−3 M) to the mobile phase (acetone: methanol=90∶10, vol/vol). The analytical values obtained by the HPLC method are very close to the calculated contents in all samples, but those obtained by spectrophotometry are high because of the interferences from overlapping of absorption bands. In the proposed HPLC method the calibration graphs of Mn(III)-chl-a and Mn(III)-chl-b are linear in the concentration range 0–20 μg cm−3 with relative standard deviations (n=10) of 3.46% and 4.54%, respectively.
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    URL: http://dx.doi.org/10.1007/BF02262249
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    Liquid chromatographic separation of the anomers and isomers of 2′-deoxyuridine (1992)
    Springer
    Chromatographia 33 (1992), S. 571-574 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 2′-Deoxyuridine ; Anomer separation ; Isomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic assay method was developed to separate 2′-deoxyuridine from its anomer and pentopyranosyl isomers. The influence of the pH of the mobile phase, the type of organic modifier and the column temperature on the chromatographic parameters was systematically investigated. Using a Hypersil C18 (5 μm) column at 10°C, the following mobile phase was found suitable: tetrahydrofuran −0.2 M potassium phosphate buffer pH 4.0-water (0.1∶5∶94.9, v/v).
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    Controlled-porosity glasses as alternative adsorbents to silica gel for HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 122-126 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Controlled-porosity glasses ; Correlation between silica and porous glass ; Hydrocarbons separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper deals with the use of controlled-porosity glasses (CPGs) as adsorbents for HPLC. The physicochemical and chromatographic properties of small-pore CPGs are compared to the analogous properties of silica gels. The results show good correlation between them and suggest the possibility of application of CPGs as adsorbents for liquid chromatography.
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    URL: http://dx.doi.org/10.1007/BF02275891
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    Retention, enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column (1992)
    Springer
    Chromatographia 33 (1992), S. 127-132 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Alpha 1-acid glycoprotein-bonded column ; Propranolol ; Propranolol ester derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an α1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.
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    URL: http://dx.doi.org/10.1007/BF02275892
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    The development and validation of a solid phase extraction/HPLC method for the determination of aflatoxins in groundnut meal (1992)
    Springer
    Chromatographia 33 (1992), S. 208-212 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Validation ; Aflatoxins in groundnut meal ; CB method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of an analytical method for the determination of aflatoxins in groundnut meal has been statistically examined. The procedure consists of a phenyl bonded phase (PH) clean-up of an acetone: water (85∶15) extract followed by HPLC quantification. Average recoveries from spiked groundnut meal extracts were calculated to be 101.3% and 101.8%, with limits of detection of 7.4 and 2.62 μg/kg for aflatoxins-B1 and-B2 respectively. Higher recoveries of aflatoxin-B1 from naturally contaminated samples were recorded using the proposed procedure than those recorded using the official AOAC (CB) method although the precisions of the two methods were not found to differ at the 5% significance level. Similar recoveries of aflatoxin-B2 were recorded for both methods but the proposed procedure was found to be more precise. The proposed PH-HPLC method was far less time consuming and more economical on solvents than the CB procedure.
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    URL: http://dx.doi.org/10.1007/BF02276184
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    Preparation of octadecyl modified column gels using heat-treated silicas and their retention behaviour in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 203-207 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl modified silica ; Hexamethyldisilazane treated silica ; Calcination ; Heat-treated silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of silanol groups on three types of octadecylmodified column gels using heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at 180°C, 500°C and 950°C, the silicas treated with octadecyldimethylchlorosilane were used for the measurement of physical and chemical analysis. From elemental carbon analysis data, the reactive silanol group concentrations, αOH(s), were determined to be 2.0 in the 180°C treated silica, 2.1 in the 500°C treated silica and 1.6 in the 950°C treated silica, respectively (original silica: mean pore diameter 116 Å, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0 μm). The separation factors, α, of pyridine versus phenol were measured to be 0.79 on 180°C treated silica, 0.91 on 500°C treated silica and 1.98 on 950°C treated silica, using acetonitrile-water mixtures as the eluent. And then, on the basis of the physico-chemical and chromatographic data, the three types of octadecyl modified column gels using heat-treated silicas by calcination have been compared.
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    URL: http://dx.doi.org/10.1007/BF02276183
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    Determination of chloride in biological fluids as pentafluorobenzylchloride by reversed-phase high-performance liquid chromatography and UV detection (1992)
    Springer
    Chromatographia 33 (1992), S. 317-320 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV detection ; Pentafluorobenzyl chloride by UV detection ; Chloride in biological fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high-performance liquid chromatographic method for the determination of chloride in plasma, urine, saliva, sweat and aqueous solution is described. Chloride, in solution in aqueous acetone, is converted by means of pentafluorobenzyl bromide into pentafluorobenzyl chloride. This derivative is separated on a ODS-5 μm reversed-phase column using isocratic elution with acctonitrile/water, 50/50, v/v, at a flow rate of 2.0 ml/min, and detected by a UV detector at 264 nm. The method is rapid, accurate and sufficiently sensitive for the determination of chloride in less than 10 μl sample volume of a biological fluid.
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    URL: http://dx.doi.org/10.1007/BF02275909
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    Liquid chromatography of carbon clusters (1992)
    Springer
    Chromatographia 33 (1992), S. 344-346 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Charge-transfer chromatography ; Carbon clusters ; Fullerenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparison of three binary mobile phases in LC separation of C60 and C70 fullerences on chemically bonded 2,4-dinitroanilinopropyl (DNAP) stationary phase was carried out, n-Hexane-benzene has been found to be the best mobile phase for efficient separation of the all-carbon molecules permitting high loads in preparative LC.
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    URL: http://dx.doi.org/10.1007/BF02275915
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    Determination of trichlormethiazide in human plasma and urine by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 339-343 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Trichlormethiazide ; Electrochemical detection ; Diuretics in plasma and urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes a high-performance liquid chromatographic (HPLC) assay method for the determination of trichlormethiazide (TCM) in human plasma and urine. After extraction and separation on an ODS column TCM from plasma was detected by oxidation in an electrochemical detector (ECD) by a porous graphite electrode. The sensitivity was better than HPLC with UV detection, enabling the determination of 2 ng ml−1 TCM in human plasma. This method also allows determination of TCM at higher concentrations by exchanging the UV for the electrochemical detector. To study the pharmacokinetics, TCM in plasma and urine was assayed with coefficients of variation in the range 2–3%. The method has the advantages of high sensitivity for plasma assay and high precision with a simple procedure for both plasma and urine samples. Small samples of 0.5 ml plasma per assay also reduced the total volume of plasma needed.
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    URL: http://dx.doi.org/10.1007/BF02275914
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    Partial separation of lactic acid enantiomers by HPLC using (S)-(+)mandelic acid as chiral mobile-phase additive (1992)
    Springer
    Chromatographia 34 (1992), S. 31-34 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral mobile-phase additive ; Inductive adsorption ; Enantiomer resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of lactic acid enantiomers by inductive adsorption has been studied on silica columns using (S)-(+)mandelic acid as the chiral mobile-phase additive. The lactic acid peak is not very strongly retained, broad, strongly tailing and splits in two at loadings lower than 60 μmol cm−2 column cross-section and at mandelic acid concentrations higher than 10−4M. The splitting indicates partial separation of enantiomers: enantiomerically enriched fractions are obtained but not enantiomerically pure. Lactic acid retention strongly decreases with increasing concentration of both hydroxy-acids; mandelic acid acts by displacement and lactic acid acts by an overloading effect.
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    URL: http://dx.doi.org/10.1007/BF02290455
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    Chromatographic resolution of racemic amines, carboxylic acids, and alcohols by a new homochiral reagent derived fromendo-borneol (1992)
    Springer
    Chromatographia 34 (1992), S. 48-50 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diastereomer separation ; Chiral derivatizing agent ; Chiral oxazolidin-2-one
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic separation of racemic amines, carboxylic acids and alcohols can be achieved with excellent resolution as measured in terms of the chromatographic separation factor α by derivatization with a homochiral oxazolidin-2-one easily prepared in three steps fromendo-borneol. The resolved materials can be isolated in excellent yields by cleavage of the resultant diastereomers using conventional methods, which also allow recovery of the chiral resolving agent for re-use.
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    URL: http://dx.doi.org/10.1007/BF02290458
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    Combined Kalman filtering and steepest descent minimization for quantitative analysis of unresolved misaligned chromatographic peaks. The resolution of alternariol and altenuisol mycotoxins in mixtures by HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 56-62 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Kalman filter ; Deconvolution ; Mycotoxins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The potential of a computational approach for the quantitative resolution of seriously overlapping chromatographic peaks when there is loss of collinearity between the pure component peaks and the mixture peak has been explored. The program makes iterative use of the Kalman filter algorithm for resolving the mixture peak with the component peaks aligned according to some values of the position parameters, and of a steepest descent minimization procedure to find the optimal alignment. This combined procedure has been applied to the quantitive resolution of the HPLC chromatograms of alternariol and altenuisol mycotoxins in synthetic mixtures and in real samples.
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    URL: http://dx.doi.org/10.1007/BF02290460
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    Direct injection analysis of hexamethylene bisacetamide in biological fluids by an HPLC column switching technique with a micellar mobile phase (1992)
    Springer
    Chromatographia 34 (1992), S. 63-66 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar mobile phase ; Direct injection of biological fluids ; Hexamethylene bisacetamide (HMBA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes the direct injection analysis of the anti-cancer drug hexamethylene bisacetamide (HMBA) in biological fluids by an HPLC column switching technique. The first chromatographic column, which provides for sample extraction and cleanup, employs a micellar mobile phase with SDS as the modifier. The second column, coupled on-line to the first, utilizes reversed-phase conditions for analysis. UV detection is employed at 210 nm. 282 samples from 12 cancer patients were analysed and good pharmacokinetics curves obtained. The drug gives recoveries of 94.0–100.9% with a relative standard deviation of 1.88%. A sample analysis is completed within 15 minutes. This method should be satisfactory not only for the analysis of HMBA but also, probably for other drugs in biological fluids.
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    URL: http://dx.doi.org/10.1007/BF02290461
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    Eluent composition effect on ion chromatographic determination of oxyanions in solutions equilibrated with soils (1992)
    Springer
    Chromatographia 34 (1992), S. 643-647 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Suppressed ion chromatography ; Eluent composition and concentration ; Oxyanions in soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methods based on simultaneous determination of oxy-anions in soil extracts are needed for studies of competitive adsorption of oxyanions by soils. We studied the effect of NaHCO3/Na2CO3 and NaOH/Na2CO3 concentrations on ion chromatographic (IC) determination of PO 4 3− , AsO 4 3− , SeO 4 2− , SeO 3 2− , WO 4 2− , and MoO 4 2− in a 10-mM NaCl matrix equilibrated with soils by using a Dionex 2002i IC unit. The eluent, 6.0 mM NaOH+4.5 mM Na2CO3, resolved the 10 mM Cl− from the six oxyanions. Elution times for Cl−, SeO 3 2− , SO 4 2− , NO 3 − , SeO 4 2− , PO 4 3− , WO 4 2− , MoO 4 2− , and AsO 4 3− were 1.7, 2.7, 5.2, 6.1, 7.8, 10.5, 14.3, 17.7, and 21.2, respectively. The recovery of 0.2-mM oxyanion standards added to the soil solutions ranged from 93.0 to 106.8%, with coefficients of variation ranging from 0 to 14.3%. The detection limits of the oxyanions studied ranged from 0.3 μM for SeO 3 2− to 9.0 μM for AsO 4 3− .
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    Comparison of post-column fluorescence derivatization and evaporative light-scattering detection to analyse saccharides selectively by LC (1992)
    Springer
    Chromatographia 34 (1992), S. 651-654 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column derivatization ; Light-scattering detection ; Carbohydrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of post-column fluorescence derivatization and evaporative light-scattering detection to analyse saccharides selectively by LC was investigated. In order to compare the performances of these two detection systems, factors such as reproducibility, detection limits and linear calibrations were determined. Despite the derivatization reaction step, post-column derivatization is superior from the standpoint of sensitivity. The detection of saccharides in beverages is also described.
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    A study of diastereoisomerism of oxovanadium schiff base chelates by gas chromatography-atomic emission spectroscopy, and high performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 269-275 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography — atomic emission spectroscopy ; Column liquid chromatography ; Metal chelate chromatography ; Diastereoisomer separation ; Vanadium complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary gas chromatography with atomic emission detection (GC-AED), and high performance liquid chromatography (HPLC) have been employed to characterize isomerism of oxovanadium N,N'-propylenebis(trifluoroacetylacetoniminate). Other tetradentate Schiff base chelates of nickel, copper and palladium are also included in this study. Element-specific detection for metal and nonmetal elements in the chelates provides a means of identifying eluted peaks. Picogram detection limits for metals by GC-AED facilitated study of kinetic behavior at low concentration.
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    Determination of ochratoxin a in beer by high-performance liquid chromatography (1999)
    Springer
    Chromatographia 49 (1999), S. 543-546 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; MS-MS detection ; Electrospray-Ionization (ESI) ; Beer ; Ochratoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ochratoxin A (OTA) is a nephrotoxic and nephrocacinogenic mycotoxin commonly produced by several ubiquitousAspergillus andPenicillium species. OTA is found predominantly in cereals and derived products, and therefore OTA may be transferred into beer from contaminated grain. Thirty-five samples of German beers were analyzed: OTA was extracted with toluene and purified by solid phase extraction using silica cartridges. OTA was determined by high-performance liquid chromatography with fluorescence detection. Since of fluorescence detection is not specific in this instance, the beer samples were also analyzed by high-performance liquid chromatography electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS). OTA levels in the range of 0.1–0.2 μg L−1 were found in 9 beer samples, 21 samples contained trace amounts of OTA (〈0.1 μg L−1) and in 5 samples no OTA was detectable.
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    Analysis of doxorubicin in cell culture media and human plasma using solid phase extraction and HPLC (1999)
    Springer
    Chromatographia 49 (1999), S. 557-561 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Doxorubicin ; Cell culture media ; Human plasma ; Fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Doxorubicin is an antineoplastic antibiotic isolated fromStreptomyces peucetius var.cesius clinically used in the treatment of tumors such as lung or breast, Hodgkin's disease and various types of leukemias. The main goal of this study was to develop a simple and sensitive HPLC method with fluorescence detection for the quantitation of doxorubicin in cell culture media collected during an in vitro studies and in human plasma. Solid phase extraction (C2 silica) was applied. The experiment established five-point standard curve (1 ng mL−1 to 100 ng mL−1). The standard curves prepared in blank cell tissue media were linear over the range of doxorubicin assayed and had a mean correlation coefficient of 0.9973±9.43×10−4 and slope 0.02545±1.85×10−3. The standard curves prepared in human plasma were linear and had mean correlation coefficient of 0.997 and slope 0.01885±5.19×10−4. The limit of quantitation for doxorubicin in both specimens was arbitrarily established to be 1 ng mL−1. Intra-day variabilities were determined using 3–4 replicates of control solutions of doxorubicin (3 ng mL−1 and 30 ng mL−1) in blank plasma and cell culture media. Inter-day variabilities were determined over a four day period analyzing replicates of controls. All precision and accuracy values fell within the acceptable range.
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    Separation of human serum albumin components by RP-HPLC and CZE and their characterization by ESI-MS (1999)
    Springer
    Chromatographia 49 (1999), S. S21 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary zone electrophoresis ; Electrospray ionization-mass spectrometry ; Human serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Human serum albumin (HSA) is one of the most abundant human proteins and has been shown to be heterogeneous. A RP-HPLC method has been developed to separate HSA components in commercially available preparations. Separations were carried out on Aquapore RP-300, C8 columns using gradient elution with a combination of acetonitrile/water mobile phases containing 0.05% trifluoroacetic acid as ion-pairing agent. Optimum resolution was attained on narrow-bore columns using a stepwise, linear gradient that incorporated a shallow intermediate step of 0.20%/min in Mobile Phase B. Under similar elution conditions, separations carried out on standard-size columns showed the expected decrease in resolution due to increased peak widths. A comparative analysis of three commercial products highlighted qualitative and quantitative differences. Capillary zone electrophoresis was used for the analysis of collected RP-HPLC fractions. Results indicated that while the HPLC separation was incomplete, one of the major HPLC peaks was primarily composed of one of the three main components typically separated by CZE. ESI-MS was used to characterize the two major RP-HPLC fractions and also showed that the HPLC separation was incomplete. The MaxEnt transform of the HPLC peaks was consistent with components all being HSA and closely related derivatives.
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    URL: http://dx.doi.org/10.1007/BF02468972
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  • 86
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    Retention behaviour of binaphthyl compounds in enantiomeric separation by microcolumn liquid chromatography with micellar bile-salt mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 58-62 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomeric separation ; Micellar bile-salt mobile phase ; Binaphthyl compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optical isomers of substituted binaphthyl, compounds such as 2,2′-dihydroxy-1,1′-dinaphthyl and 1,1′-binaphthyl-2,2′-diyl hydrogenphosphate are, separated by HPLC using micellar bile-salt mobile phases. Operating conditions which affect the optical resolution of these enantiomers are examined. The largest separation factor achieved for these enantiomers is 2.74. The elution order of the latter enantiomers changes with mobile phase composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276853
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  • 87
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    Retention mechanism of enantiomeric separation by liquid chromatography with micellar bile-salt mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 63-66 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar bile-salt mobile phase ; Enantiomeric resolution ; Retention model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention mechanism involved in enantiomeric separation of binaphthyl compounds by HPLC with micellar bilesalt mobile phases is discussed. A new model for the equilibrium is proposed, in which a heterogeneous stationary phase comprising solvated and micelle-adsorbed portions is considered. The experimental data supported the adsorption of the bile salt micelles on the octadecylsilica stationary phase which could recognize the chirality of binaphthyl compounds.
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    URL: http://dx.doi.org/10.1007/BF02276854
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  • 88
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    Purification of the glycosylated beta subunit of (Na,K)-ATPase by lectin affinity chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 521-524 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Affinity chromatography ; (Na,K)-ATPase β-subunit ; Wheat germ agglutinin ; Protein purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Wheat germ agglutinin (WGA) affinity chromatography was examined as a method for the purification of the glycosylated beta subunit from SDS solubilized (Na,K)-ATPase. This lectin, WGA, bound quantitatively all of the beta subunit from SDS solubilized (Na,K)-ATPase whether or not the sample was reduced and/r alkylated. The combination of affinity and high performance size exclusion chromatography purified the beta subunit to a single band on SDS-PAGE electrophoresis. Compared to other methods of isolation this two step procedure utilizing wheat germ agglutinin was superior in terms of yield and purity for the beta subunit of (Na,K)-ATPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262242
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  • 89
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    Quantitative structure-enationselective retention relationships for the chromatography of 1,4-benzodiazepines on a human serum albumin based HPLC chiral stationary phase: An approach to the computational prediction of retention and enantioselectivity (1992)
    Springer
    Chromatographia 33 (1992), S. 546-550 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Benzodiazepines ; Human serum albumin chiral stationary phase (HSA-CSP) ; Quantitative structure-enantiospecific retention relationships (QSERR) ; Structural descriptors ; Submolecular polarity parameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Quantitative structure-enantiospecific retention relation-ships (QSERR) have been derived for a series of 1,4-benzodiazepines. The compounds were chromatographed on a human serum albumin based HPLC chiral stationary phase (HSA-CSP). Molecular modeling of the solutes allowed the determiantion of various structural descriptors. Among these descriptors, a submolecular polarity parameter, PSM, was identified which was able to characterize enantiospecific interactions of benzodiazepines with the HSA-CSP. Combining PSM with the retention parameter of the less retained enantiomer permitted precise prediction of the retention of the second eluting enantiomer. Highly statistically significant regression equations were also derived which described the retentions of both enantiomers in terms of nonempirical molecular descriptors. The calculated enantioselectivity correlated well with the experimentally observed values. A significant conclusion from this study is support for the existence of two different binding sites for chiral benzodiazepines on HSA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262246
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  • 90
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    Evaluation of analytical methods. Analysis of minocycline by liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 560-566 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Official methods of analysis ; Method evaluation ; Minocycline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The liquid chromatographic methods laid out for the analysis of minocycline hydrochloride in the British Pharmacopoeia 1988, the United States Pharmacopeia XXII and the Pharmacopée Française 10 were examined. The major difference between these methods lies in the adjustment of the pH of the mobile phase. The analyst has to obtain the right pH of the mobile phase for his available column. This was found to be a less than easy task for the occasional analyst. Other disadvantages observed were poor solubility of the components of the mobile phase, reduced sensitivity due to UV absorbance by the mobile phase, rather high back pressure, the elution order for 9-minocycline depending on the brand of stationary phase, and above all, poor stability of the stationary phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262248
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  • 91
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    Ion-pair, liquid chromatographic analysis of total gossypol in chicken liver (1992)
    Springer
    Chromatographia 33 (1992), S. 174-176 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair system ; Gossypol analysis ; Chicken liver ; Plant toxin residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair, liquid chromatographic method for the determination of total gossypol in chicken liver has been developed. It involves hydrolysis of bound gossypol in the presence of ascorbic acid, partitioning into chloroform and isocratic separation on Spherisorb ODS2, 10 μm, column with a methanol-water mobile phase containing octane-1-sulfonate. Precision data based on within-day and between-days variation suggested an overall relative standard deviation of 8.1%, while overall recovery was 81.1%±3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275901
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  • 92
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    Energetics of hydrophobic solute retention on reversed-phase chromatography supports: Effects of solute, solvent, and sorbent properties (1992)
    Springer
    Chromatographia 33 (1992), S. 403-412 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic solutes ; Enthalpy and entropy changes ; Eluent composition effects ; Surface area effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic retention of several nonpolar solutes by three reversed-phase liquid chromatography (RPLC) supports was measured at several temperatures with binary mixtures of methanol/water and acetonitrile/water as the mobile phase. These data were used to estimate enthalpy and entropy changes (ΔH sorp o and ΔS sorp o ) associated with solute retention. The dependence of these two thermodynamic parameters on organic solvent content (θ) in the mobile phase, solute hydrophobic surface area (HSA), and bonded n-alkyl chain length (Nc) of the RPLC support was evaluated. The differences noted in the two solvent mixtures were attributed to: (1) the manner in which solvent surface tension changes with increasing θ, and (2) the differences in the interaction of methanol and acetonitrile with the bonded alkyl chains.
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    URL: http://dx.doi.org/10.1007/BF02262319
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  • 93
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    Determination of triazine herbicides in surface and drinking waters by off-line combination of liquid chromatography and gas chromatography-mass spectrometry (1992)
    Springer
    Chromatographia 34 (1992), S. 5-13 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography-mass spectrometry ; Water analysis ; Triazine herbicides ; Chemical ionization mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Mass spectra of 12 triazines were obtained by electron impact (EI), positive-ion chemical ionization (PCI) and negative-ion chemical ionization (NCI) using methane and isobutane as reagent gases. EI mass spectrometry is more sensitive than PCI and NCI, although the chemical ionization modes increase selectivity markedly. A pre-column packed with polymer stationary phase was employed to preconcentrate surface and drinking water samples. After desorption of the analytes with ethyl acetate, an aliquot was injected directly into the GC-MS system. Atrazine and simizine were found in these samples at 10–80 ppt levels. The limits of detection for both herbicides were below 10 ppt in drinking water.
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    URL: http://dx.doi.org/10.1007/BF02290451
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  • 94
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    Combined effect of organic modifier concentration and column temperature on retention in reversed-phase ion-pair liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 14-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pairing ; Temperature effects ; Organic modifier concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behavior of phenylamine and naphthylamine sulphonic acid was evaluated in reversed-phase ion-pair liquid chromatography as a function of organic modifier concentration and column temperature. It has been observed that the logarithm of capacity factors decrease linearly with organic modifier concentration, and there is a good linear relationship between the intercept and slope for this relationship. Phenylamine and naphthylamine sulphonic acid retention decreases with increase in column temperature. A linear dependence of lnk ip ′ on the reciprocal of the absolute temperature, the Van't Hoff plot, was observed over the column temperature range studied, and the standard enhalpic change (ΔHo) for these sulphonic acid transfers from the mobile phaser to the stationary phase was determined. ΔHo was dependent on the solute structure and in the range from 2.5 Kcal/mol to 5.5 Kcal/mol, which is close to that observed in RP-HPLC. The enthalpy/entropy compensation effect was evaluated by plotting lnk ip(T) ′ vs. −ΔHo, and the apparent differences in retention mechanisms between the analytes were observed, which may arise from the significant differences in their configuration, hydrophobicity and the charges of the solutes as well as the complex retention processes of RP-IPC.
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    URL: http://dx.doi.org/10.1007/BF02290452
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  • 95
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    Partial resolution of molecular species during liquid chromatography of soybean phospholipids and effect on quantitation by light-scattering (1992)
    Springer
    Chromatographia 34 (1992), S. 557-562 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Soybean lecithin ; Partial resolution ; Light scattering detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using both synthetic phospholipids and soybean phosphatidylcholine (PC), it is shown that the retention of phospholipids during normal-phase chromatography is not only determined by the polar headgroup, but also by the fatty acid composition. Although fatty acid methyl ester determinations reveal that this effect only causes an enrichment of some fatty acids in subsequent fractions of the same phospholipid class, still a large influence on the peak shape is observed. As a further consequence, the evaporative light scattering detector output is greatly affected, so that accurate quantitation of phospholipid classes requires the availability of standards of the same origin.
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    URL: http://dx.doi.org/10.1007/BF02269863
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    FMOC-Cl as derivatizing agent for the analysis of amino acids and dipeptides by the absolute analysis method (1999)
    Springer
    Chromatographia 49 (1999), S. 317-320 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino acids ; FMOC derivatives ; Oligopeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary One classical method for quantitation of amino acids in proteins is hydrolysis of the proteins and determination of the free amino acids. Although the drastic experimental conditions necessary for complete hydrolysis always cause degradation of some of the amino acids, if mild hydrolysis conditions are used, a mixture of amino acids and oligopeptides is obtained. If these conditions are adequately tuned, the oligopeptides are almost exclusively dipeptides. For this reason we have initiated a study to find a derivatizing agent suitable for the analysis of amino acids and dipeptides by an absolute method of quantitation already tested for amino acids. FMOC-Cl was found to be a suitable derivatizing agent for this purpose.
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    URL: http://dx.doi.org/10.1007/BF02467563
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    High-performance liquid chromatographic determination/identification of oxytetracycline and sulphadimidine in meat and eggs (1999)
    Springer
    Chromatographia 49 (1999), S. 369-373 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sep-Pak CN cartridge ; Oxytetracycline ; Sulphadimidine ; Meat and eggs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method for the simultaneous determination/identification of residual oxytetracycline (OTC) and sulphadimidine (SDD) in meats (beef, pork, chicken) and eggs by high-performance liquid chromatography (HPLC) was developed. The extraction of OTC and SDD was performed using a Sep-Pak® CN cartridge. The extracts contained OTC/SDD analytes when examined by HPLC using a LiChrospher® 100 RP-8 end-capped column and a mobile phase of acetonitrile-acetic acid-water (28:4:68, v/v/v) with a photodiode array detector. The average recoveries from spiked samples (0.1 μg g−1 and 1.0 μg g−1) were in excess of 80.2% with coefficients of variation between 1.5 and 5.0%. The limits of detection for OTC and SDD were 0.05 and 0.02 μg g−1, respectively.
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    URL: http://dx.doi.org/10.1007/BF02467608
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    Improved separation of polyethylene glycols widely differing in molecular weight range by reversed-phase high performance liquid chromatography and evaporative light scattering detection (1999)
    Springer
    Chromatographia 49 (1999), S. 615-620 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Evaporative light-scattering detection ; MALDI-TOF ; Polyethylene glycols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polyethylene glycols (PEGs) of nominal molecular weight (M) 200, 400, 600, 1000, 1500, 3000, 4000 and 6000 were chosen as model compounds and subjected to reversed-phase high performance liquid chromatography (RP-HPLC) on an octadecasilyl silica gel (C18) stationary phase using a binary gradient composed of acetonitrile and water and evaporative light scattering detection (ELSD). Satisfactory resolution of oligomers up to M of 3000 was accomplished; the higher M samples PEG-4000 and PEG-6000 could not be further resolved into the constituent oligomers and therefore, M=4000 marks the upper limit of oligomer resolution. Despite some peak overlapping as a consequence of the more or less broad oligomer distribution, individual types of PEG samples can be distinguished from each other by their characteristic chromatographic fingerprint patterns, as shown with a mixture consisting of PEG-400, PEG-1000, PEG-3000, PEG-4000 and PEG-6000. For this reason, the method is well-suited for characterization of samples containing PEGs widely differing in M. In addition, matrix assisted laser desorption ionization time of flight mass spectroscopy (MALDI-TOF/MS) performed with PEG-600, PEG-1000 and PEG-3000 revealed that the optimum degree of oligomer resolution has been achieved by use of the present method.
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    URL: http://dx.doi.org/10.1007/BF02466902
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  • 99
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    Separation of the enantiomers of amino and amide compounds on novel chiral stationary phases derived from a crown ether (1999)
    Springer
    Chromatographia 49 (1999), S. 621-627 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phases ; Crown ether derivatives ; Amino compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantiomers of primary amino compounds have previously been resolved on a chiral stationary phase (CSP) CSP-18C6I, prepared by immobilizing (+)-18-crown-6 tetracarboxylic acid. In this study related chiral stationary phases were prepared in an effort to broaden the scope of CSP18C6I. CSP-18C6II, synthesized to investigate the effect of spacer length, resolved the enantiomers of 2-amino-1,2-diphenylethanol and 1-(1-naphthyl)ethylamine (1-NEA) (hydrophobic amino compounds) with the largerk values and smaller α values than on CSP-18C6I, probably because of the greater hydrophobicity of CSP-18C6II. Use of CSP-18C6III, synthesized by modification of carboxylic acid functionality of CSP-18C6II by introduction of another chiral moiety,S-1-NEA, resulted in larger α values for 2-amino-1-phenylethanol and 2-amino-1-phenylpropanol than on CSP-18C6II, but the enantiomers of 1-NEA were not resolved, because of steric hindrance between 1-NEA and the chiral moiety. The amide derivativeN-3,5-dinitrobenzoyl-1-(α-naphthyl)ethylamine (DNN) as π-acceptor (3,5-dinitrobenzoyl function) or π-donor (naphthylethylamide function), and no primary amino functionality, was resolved on CSP-18C6III. The mechanism of separation of the enantiomers of DNN was assumed to be the π−π interaction between the 3,5-dinitrobenzoyl function (π-acceptor) of DNN and theS-1-NEA moiety (π-donor) of CSP-18C6III.
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    URL: http://dx.doi.org/10.1007/BF02466903
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  • 100
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    Determination of alcohols using condensation agent carbazole-9-acetyl-benzene-disulfonate by high performance liquid chromatography with pre-column fluorescence derivatization (1999)
    Springer
    Chromatographia 49 (1999), S. 657-665 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alcohols ; Pre-column fluorescence derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive LC method for the determination of alcohols, using fluorescent condensation agent carbazole-9-N-acetylbenzne-disulfonate(CABS), has been developed. A mixture of alcohols and triethylamine catalyst in dichloromethane or chloroform is treated with CABS to give quantitative yields of esters. Emission maximum for the derivatized alcohols is 365 nm (λex 335 nm). The labeled derivatives are very stable, no significant decomposition is observed after heating in 40% at 40°C for 24 h. The method, in conjunction with a multigradient program, offers baseline resolution of common alcohol derivatives on a reversed-phase C18 column. Studies on derivatization conditions indicate that primary and secondary alcohols react very fast with CABS in the presence of triethylamine in dichloromethane or chloroform to give the corresponding fluorescent derivatives. This method is more convenient and more efficient than previous methods which require prior conversion of carboxylic acids to acyl chlorides. The separation of alcohol derivatives has good reproducibility and the rsd's (n=5) for 50 pmol of each alcohol are 4%. Detection limits are at the fmol level.
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    URL: http://dx.doi.org/10.1007/BF02466908
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