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  • Column liquid chromatography  (349)
  • Gas chromatography  (172)
  • Springer  (516)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • 1985-1989  (516)
  • 1935-1939
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  • Springer  (516)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • Wiley-Blackwell  (108)
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Year
  • 1
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    Chromatographia 27 (1989), S. 27-30 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 1,ω-Di(alkoxy)-polysulphides ; Retention contributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reaction of S2Cl2 with alcohols yields products, the reversed-phase liquid chromatograms of which are similar to those of dialkyl-polysulphides RSnR, i.e., they represent homologous series. Four of the products were identified via GC-MS as 1,ω-di(alkoxy)-polysulphides having the general structure ROSnOR. Retention contributions of alkyl groups R and sulphur atoms in the −Sn — chain are not much different from values observed with polysulphides. The effect of oxygen, however, is only about −100 index units per O atom, while in dialkyl ethers values of −500 units have been reported.
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  • 2
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    Chromatographia 27 (1989), S. 5-14 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention behaviour ; Column parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of small molecules on reversed phase or other hydrophobic stationary phases can be represented by k′ values of members of a homologous series at varying solvent compositions. The evaluation of simple linear relationships leads to the introduction of a set of four parameters that contain all the information about retention behaviour of this homologous series in the binary solvent system chosen. It is possible to extrapolate to a hypothetical non-hydrophobic molecule and a solvent, the polarity of which equals that of the stationary phase, to characterize the properties of the stationary phase — eluent system. In addition, a chromatographic method for determination of the phase ratio of the column is proposed.
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  • 3
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    Chromatographia 27 (1989), S. 37-43 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methylbromide ; Charcoal tubes ; Pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Air sampling of methylbromide using 900 mg HBr-treated activated charcoal tubes, followed by solvent desorption and FID or ECD chromatographic analysis, makes it possible to evaluate concentrations ranging from 0.2 ppm (1 mg×m−3) to 250 ppm (1g×m−3) at ambient temperature even with a high hygrometric level. Thermal desorption does not lead to satisfactory results.
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  • 4
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    Chromatographia 27 (1989), S. 60-66 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass loadability ; Stationary phase capacity ; Capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In GLC the mass load can be normalized with respect to the amount of stationary phase in one plate. This quantity can be used for a specified solute-liquid phase combination in any capillary or packed column, irrespective of the column dimensions or the number of plates. For each individual solute in a given stationary phase a unique factor β″ can be found, which accounts for the specific shape of the isotherm of this particular combination. this factor β″ corresponds well with the activity coefficients of the solutes in the stationary phase, by which a fairly good approximation of the mass loadability of the column at hand can be made without need for experiment.
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  • 5
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange separation ; Preparative separations ; Human chorionic gonadotropin hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatography (HPLC) method was developed for the purification of 50mg crude human chorionic gonadotropin (HCG) hormone sample in one chromatographic run on a 250×10 mm SERVA DEAE Poliol-Si-500 column. During the 60-minute linear gradient of 0.05 M sodium sulfate, 0.05 M sodium hydrogen sulfate and 0.05% (v/v) acetonitrile in buffer “B” complete separation was accomplished in 40 min. Identity and purity of the fractions were checked by SDS electrophoretic method. The eluted HCG fractions were dialyzed for 24 hours to remove the buffer salts and liophilized. The activity of the hormone did not decreased significantly during the purification procedure.
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  • 6
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microcrystalline cellulose triacetate ; Molecular modeling ; Computer graphics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Molecular modeling and energy calculations have been used to study the chromatographic separation of aromatic compounds on microcrystalline cellubose triacetate. A linear relationship has been found between the logarithms of the capacity factors and the energy values of the interaction of these compounds with this stationary phase. The interaction energies have been calculated for two different spatial dispositions of the solutes in relation to the sorbent.
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  • 7
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Liquid crystals ; Synthesis of new bonded phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A compound which becomes a liquid crystal when bonded to a polysiloxane was reacted with dimethylchlorosilane to produce a reagent suitable for bonding to a silica surface. After the silanization reaction was complete, the product was characterized by elemental analysis, diffuse reflectance Fourier transform Infrared Spectroscopy (DRIFT), CP/MAS carbon-13 NMR and differential scanning calorimetry (DSC). Preliminary chromatographic testing was done by retention index measurements using the alkylarylketone homologous series and by measuring the separation factor, α, for anthracene/phenanthrene at two different mobile phase compositions.
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  • 8
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    Chromatographia 27 (1989), S. 552-558 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Radio gas chromatography ; 3H- and14C-labelled compounds ; Isotope effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Radio gas chromatography (RGC) is a valuable tool for the analysis of radioactively labelled compounds. Recent advances in capillary GC, especially in column technology and instrumentation have also induced new possibilities in this field. With regard to the preservation of the achieved separation efficiency, radioactivity detection is the main problem in capillary RGC. Based on published data and on our extensive experience in conventional RGC, a simple, reliable and versatile method has been developed for the radioactive detection: purge gas is added to the effluent of the capillary column and the RGC detection unit with conversion tube and flow-through proportional counter is used maintaining small dead volumes and dimensions. The influence of the extra-column volumes and of the total gas flow rate (of the carrier, purge and quenching gases) on the peak shape was investigated. It was also found that the isotopic effect commonly known in GC of2H- and3H-labelled compounds is hardly measurable for larger [G-14C] labelled species such as [G-14C] labelled higher fatty acids with high isotopic abundance of14C, even on the highly efficient capillary columns. The quantitative aspects of the detection method used are discussed and some applications to the analysis of labelled biochemicals (amino and fatty acids) are demonstrated.
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  • 9
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    Chromatographia 27 (1989), S. 644-648 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ion exchange resins ; Polymeric supports ; Chloromethanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of compounds of various classes on macroporous sulfonated cation exchangers in the form of the fourth period elements in Mendeleev's table (i. e. in the K, Ca, Co, Ni, Cu, Zn-forms) has been investigated. It has been shown that these sorbents are characterized by a high specificity of molecular interaction. It has also been established that the gas-chromatographic properties of cation exchangers depend on the nature and valency of the metal ion in the ionogenic group.
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  • 10
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    Chromatographia 27 (1989), S. 633-638 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adsorption isotherms ; Equilibria criteria ; Silica and carbon adsorbents ; Aromatic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Examples of high-performance liquid chromatography (HPLC) are given for the determination of adsorption equilibrium and distribution coefficients, calculation of excess adsorption isotherms from solutions ranging from 10−7 to 10−1 mole fraction, changes in activity coefficient of the component predominantly adsorbed from solution and substitution enthalpy. These examples stem from studies of HPLC and the static adsorption of benzene, anisole and benzaldehyde from solutions in n-heptane on macroporous silica and active carbon at various temperatures. A criterion is suggested for evaluating equilibrium in the HPLC process. The potential of size-exclusion chromatography (SEC) for evaluating the volume and predominant diameter of adsorbed pores as well as pore diffraction are discussed. Prospects for HPLC application to molecularstructural analysis and other purposes are discussed briefly.
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  • 11
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    Chromatographia 27 (1989), S. 109-112 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Packed columns ; Immobilized stationary phase ; Poly(ethylene glycol) phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Carbowax 20M poly(ethylene glycol) stationary phase was immobilized on Chromosorb W by cross-linking with pluriisocyanate. The properties of the prepared packing material were investigated. Column efficiencies of 10,960 and 7,510 theoretical plates/meter were obtained for n-pentadecane and 1-heptanol, respectively.
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  • 12
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    Chromatographia 27 (1989), S. 118-122 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase chromatography ; Non-aqueous reversed-phase chromatography ; Polycyclic aromatic hydrocarbons ; Solvent strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Elution strengths of 11 common HPLC solvents on a polymeric C18 phase were compared using a marker set of polycyclic aromatic hydrocarbons. Naphthalene, pyrene, benzo[ghi]perylene, and three larger naphthologues of 8, 10, and 12 rings (constituting a “naphthalene zigzag” series) were chosen because they span the solvent strength range up to and including the strongest solvents, tetrahydrofuran (THF) and chlorobenzene. Four pairs of similarly shaped isomers were used to probe solvent selectivity. With the exception of THF, HPLC solvent strength correlated with observed red shifts of fluorescence band maxima in each solvent. For THF, the pure solvent and blended mixtures behaved quite differently.
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  • 13
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    Chromatographia 27 (1989), S. 156-158 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mobile phase retention time ; Capacity factor ; Negative capacity factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Numerous ideas and procedures have been suggested in the literature for the determination of tm, the retention time of a non-retained species, in high-performance liquid chromatography. In some cases chromatograms have been obtained showing sample components eluting prior to the assumed non-retained species. This phenomenon results in apparent negative capacity factors for the species in question. We have proposed a method employing small inorganic anions which results in a limiting value for tm and eliminates apparent negative capacity factors.
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  • 14
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    Chromatographia 27 (1989), S. 159-163 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Flame photometric detector ; Sulfur compounds ; Response quenching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The long time retardation of the main hydrocarbon peak in the chimney of the flame photometric detector greatly reduces the responses of later-eluting sulfur compounds. In the absence of hydrocarbons in the flame, the slope (s) of the log I vs. log [S] plot (where I is the sulfur response and [S] is the sulfur concentration in the sample) is of the highest value and is constant for all experimental conditions tested. Flame hydrocarbons cause the s value to decrease, and this is dependent on the oxygen to hydrogen ratio in the flame (O/H) and, under certain conditions, also on the sulfur to carbon ratio (S/C) of the sample. The abnormalities observed in the determination of methyl thiol in natural gas are explained on the basis of the present study.
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  • 15
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    Chromatographia 27 (1989), S. 228-232 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase ; 13C n.m.r. ; Arginine-aldehyde peptides ; GYKI-14166
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatographic and13C n.m.r. spectrometry methods were used for the investigation of peptides containing arginine-aldehyde moiety. Investigation of a model compound, N-benzoyl-Arg-H, showed that in an acidic mobile phase peptides containing the arginine-aldehyde group elute in three characteristic peaks. The components of the peaks were found to be constituents of an equilibrium mixture. The structures of the two components were identified, one as the aldehyde hydrate, the other as the cyclanol derivative. The reactivity of TRIS (HCl) buffer at pH 8.5 with the arginine aldehyde moiety was used for the assignment of the equilibrium structures.
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  • 16
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    Chromatographia 27 (1989), S. 631-632 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Wide-bore glass capillary columns ; End-sealing ; Static coating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An end-sealing method to be used for static coating of wide-bore glass capillaries is described. After the capillary was completely filled with the coating solution, one end is connected to a gas-tight syringe (10-ml volume) via silicone tubing and the other end is fixed with shortcutted silicone tubing for sealing with a plug. The method is highly successful.
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  • 17
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase ; Ion-pair ; Recoveries ; Hepatocytes ; Purine compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three groups of metabolites were analyzed in extracts of rat hepatocytes by an HPLC method: (i) nucleotides (ATP, ADP, AMP, GTP, GDP, UTP, UDP, IMP, UMP), (ii) nucleosides and nucleobases (adenosine, adenine, guanosine, inosine, xanthine, hypoxanthine, uridine) and (iii) inhibitors of xanthine oxidoreductase (oxypurinol, allopurinol). Perchloric acid extracts were neutralized with K2CO3/triethanolamine and analyzed at 254 nm by reversed-phase ion-pair high-performance liquid chromatography. The nucleotides and their derivatives were separated with a gradient elution using 10 mM NH4H2PO4/2 mM t-butylammonium-phosphate and acetonitrile. Recovery values were estimated for the extraction procedure used. The method was applied to the investigation of nucleotide metabolism of hepatocytes of starved rats at anoxia and reoxygenation.
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  • 18
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    Chromatographia 27 (1989), S. 316-320 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Silica-based cation-exchanger ; Trimethylsilyl chlorosulfonate ; Lanthanides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A low exchange-capacity, silica-based cation-exchanger for use in ion chromatography has been synthesized. (p-Trimethylsilyl)benzyl-dimethylchlorosilane (TBDCS) reacts with trimethylsilyl chlorosulfonate (TMCS) to produce a compound sulfonated in the para position of the type ArSO2OSi (CH3)3, which is bonded to 5 μm porous silica beads and hydrolysed to the corresponding arylsulfonic acid. The product is hydrophilic and has a high degree of sulfonation, efficiencies of packed columns reaching about 40,000–50,000 plates per meter for the separation of the Mn2+ ion. The new stationary phase has been applied to the ion chromatography of some organic and inorganic ions. It is notable that 14 lanthanides can be separated by isocratic elution about one hour on a 150×4·6 mm column, with 4 mM ethylenediamine and 6 mM α-hydroxyl-isobutanoic acid (pH 3.67) as mobile phase.
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  • 19
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    Chromatographia 27 (1989), S. 191-193 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dansyl amino acids ; Chemiluminescence ; Bis(2,4,6-Trichlorophenyl)oxalate, (TCPO) ; Enhancement of luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The dansylated amino acids alanine, glutamic acid, methionine and norleucine were separated by reversedphase HPLC and detected via chemical excitation using the post-column, TCPO-peroxyoxalate reaction system. Enhancement of the chemiluminescence emission was achieved by including the surfactant Triton X-100 in the eluent.
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  • 20
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ethyl carbamate ; Direct injection quantification ; Cold injection system ; Optimised SIM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An integrated procedure is described which allows direct injection quantitative screening to single figure parts per billion (μg/L) levels of ethyl carbamate in the natural matrix of distilled alcoholic beverage. Injection and detection performance was studied and optimized to allow this routine, reproducible, trace analysis without any sample pre-treatment. All aspects of the analysis including autosampler run sequences and automated internal standard report generation are initiated and controlled from a single GC/MS workstation.
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  • 21
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reverse-phase chromatography ; Elastin Hydrolysis measurement ; On-line post-column derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Excessive breakdown of elastin, a structural protein, may be related to aortic disease and emphysema. Since L-valyl-L-proline occurs in high concentrations in elastin, a rapid and sensitive method using HPLC with post-column on-line derivatization was used to measure the dipeptide from swine aortic tissue, and the amount of elastin present was determined. Elastin was extracted by alkaline hydrolysis. After neutralization and filtration, the sample was injected onto a ODS-2 gel column, and the dipeptide was eluted by a linear gradient of 0 to 10% of 1-propanol in 50 mM heptafluorobutyrate, pH 3, at a flow rate of 1 ml/min. The eluent was reacted with fluorescamine at pH 8.6, and fluorescence was detected at an excitation wavelength of 395 nm and a 455 nm cutoff emission filter.
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  • 22
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    Chromatographia 27 (1989), S. 449-454 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exchange and affinity columns in series ; Porcine pancreatic enzymes ; Trypsin and elastase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to separate and purify some of the enzymes contained in porcine pancreas, operation of an ion-exchange column in series with an affinity column has been used. The enzymes dealt with possess very similar molecular weights, isoelectric points and active sites. Hence they are difficult to separate and purify by traditional separation and/or purification methods. CM-Sepharose anion-exchange resin adsorbs elastase and trypsin at low pH (4.5) and desorbs them at high pH (9.0) and high ionic strength. Chitin-CHOM affinity adsorbent adsorbs trypsin at high pH (8.0) and desorbs it at low pH (2.5). By virtue of this complementary relationship two chromatographic columns were connected in series for facilitating the separation and purification of elastase and trypsin from porcine pancreas. The result showed that the specific activities of elastase and trypsin had been increased 16 and 22 fold respectively.
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  • 23
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    Chromatographia 27 (1989), S. 455-460 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Surface free energy ; Silane-covered materials ; Film pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The surface free energy, or film pressure, π0, is measured for mica (Mica HK), silane-covered mica (Mica NP), Chromosorb W DMCS and glass beads. The film pressure is obtained from gas chromatography. The materials are used as adsorbents and benzyl alcohol and n-dodecane are used as molecular probes. Adsorption isotherms at 353 K are obtained from gas chromatography data and the surface free energy is computed with the help of the Gibbs equation. Values of π0 for a given surface are found to vary with the molecular probe. With benzyl alcohol π0 varies from 44 erg/cm2 for Mica 60 HK to 76 erg/cm2 for glass. In the case of n-dodecane π0 is found to vary in the same manner but the values range from 25 to 45 erg/cm2. The results are in good agreement with the values obtained with the contact angle method.
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  • 24
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    Chromatographia 27 (1989), S. 469-471 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace analysis ; Ethylene oxide ; Capillary column
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A headspace gas chromatographic method for determination of traces of ethylene oxide (EO) in sterilized materials has been developed. The method allows the determination of the amount of EO by putting the samples directly into acetonitrile and analysing by means of headspace GC. The procedure described is simple, sensitive, reproducible and linear. The lower limit of detection is 0.015 μg/g of sterilized material.
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  • 25
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    Chromatographia 27 (1989), S. 472-474 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrous titanium oxide ; Anion exchange ; Polyvalent anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hydrous titanium oxide (HTiO), prepared under varying conditions of precipitation, has been studied for its anion exchange behaviour. Its chemical and thermal stability has been examined. The stoichiometry of uptake for Cl− has been investigated using a36Cl radiotracer and the regeneration power of the exchanger checked. Distribution coefficients for halides and polyvalent anions have been determined and on the basis of sorption data some polyvalent anions have been separated using HTiO columns.
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  • 26
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    Chromatographia 27 (1989), S. 509-512 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flavonoids ; Crataegus ; Passiflora ; Matricaria ; Ginkgo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Flavonoids of Crataegus monogyna, Passiflora incarnata, Matricaria chamomilla and Ginkgo biloba extracts have been separated by isocratic elution on C18 columns using eluents based on C3 alcohols, tetrahydrofuran or dioxane. Satisfactory results have been obtained at compared to the low resolution achieved with the customary system acetonitrile-water-acetic acid.
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  • 27
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    Chromatographia 28 (1989), S. 19-23 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Preparation of stationary phases ; Polymer coated stationary phases ; Polymer-octyl bonded phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polymethyloctylsiloxane-coated stationary phases have been prepared for liquid chromatography, by thermal reaction. The influence of the reaction conditions on retention and efficiency of test substances with different structures has been discussed. The materials have good stability in both acidic and basic eluents.
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  • 28
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size exclusion ; Vesicular packing material ; Proteins and polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new vesicular packing material — prepared from plant cell clusters by purification of the intact cell wall framework —is suitable for chromatography, giving high performance at low pressure gradients. The separation is achieved by dialysis through the cell wall, which is an ultrafilter membrane with an extremely sharp size limit of separation. Almost the whole of the stationary liquid phase is located within the vesicle (empty cell) lumina. In contrast to gel filtration vesicle chromatography gives a practically ideal separation of two size groups with an extremely short fractionation range. The size limit of separation was investigated by chromatography of proteins and other polymers. Group separation of molecules of a polydisperse dextran standard preparation showed that the critical Stokes' diameter for dextran permeation into the stationary liquid phase of the vesicular packing is 5 to 6 nm.
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  • 29
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Preparative scale separation ; 1,1-Dimethylethyl 4- and 5-bromo-trans-2-methylcyclohexane-1-carboxylate ; Trimedlure-related isomers ; Ceratitis capitata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A semi-preparative high-performance liquid chromatographic procedure on 5-μm silica was developed for the isolation of gram quantities of four 1,1-dimethylethyl 4- and 5-bromo-trans-2-methylcyclohexane-1-carboxylate isomers (trimedlure-related) for NMR studies and comparative biological evaluation as male medfly,Ceratitis capitata, attractants.
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  • 30
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detection ; Pseudouridine ; Creatinine ; Urine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The anodic behaviour of pseudouridine a modified nucleoside proposed as tumoral marker, has been studied at a mercury electrode. A method for its determination in urine samples by liquid chromatography with indirect anodic polarographic detection has been developed. The method is simple, highly selective and permits the direct injection of urine after dilution (1∶20) with mobile phase. Creatinine, which also gave an anodic response on mercury, could be simultaneously determined and used as an “internal standard” for Psi. This allowed the pseudouridine/creatinine ratio determination in a single run on the same specimen and the use of urine samples collected randomly instead of the 24h collection. The within-day RSD% for pseudouridine/ creatinine peak areas ratio was 3.4%.
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  • 31
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    Chromatographia 28 (1989), S. 9-14 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ester silicate silica gels ; Behaviour with organic bases ; Silanol groups ; Acidic centres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Silica gels produced from ester silicates (ES-gels) are excellent chromatographic supports. In comparison with other silica gels the RP-materials obtained from them show little peak tailing even with polar, and, in particular, with basic compounds. Gels produced by various manufacturing processes have been classified by adsorption with methyl pyridinium chloride. ES-gels yield very low methyl pyridinium chloride values and small asymmetry parameters. The results indicate that there are strongly acidic, structurally-related surface centres which cause peak tailing on most commercial gels. It was shown that surface silanols on silica gels do not, in themselves, lead to peak tailing.
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  • 32
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    Chromatographia 28 (1989), S. 24-26 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Anesthetics ; Pharmacokinetics
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    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive capillary gas chromatographic method is described for the simultaneous determination of lidocaine, tetracaine, procaine and dibucaine. The method was applied to the determination of anesthetics in tissue homogenates incubated at 38°C at doses between 10 and 400 mg/kg. In the liver tissue thein vitro metabolization of the studied anesthetics is most rapid for tetracaine, also fast for procaine, while for lidocaine and dibucaine the metabolization is very slow. In brain tissue thein vitro metabolization of anesthetics is very slow. The method shows good analytical parameters: linearity between 5 and 40 μg/ml; day-to-day reproducibility ca. 8% for a concentration of 20 μg/ml, precision ca. 7% for a concentration of 20μg/ml. Accuracy is also very good.
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  • 33
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    Chromatographia 28 (1989), S. 34-38 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Methylisothiazolones ; Preservatives ; Analysis of cosmetics
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    Topics: Chemistry and Pharmacology
    Notes: Summary Antimicrobially active formulations based on 2-methyl-3(2H)-isothiazolone and 5-chloro-2-methyl-3(2H)-isothiazolone (Kathon CG, Euxyl K 100) are incorporated into manufactured cosmetics as preservatives. In this paper we report on the analysis of these active components by means of liquid chromatography. It is conventional for the original methylisothiazolone components in cosmetics to be analyzed by reversed phase high-performance liquid chromatography after column chromatographic separation and flash chromatographic purification. In our new analytical method the methylisothiazolones are converted into the respective β-thiosubstituted acrylamide derivatives, which are ionic substances, with the help of the nucleophilic reagent hydrogensulfite. An ion pair high-performance liquid chromatographic method has been developed for the separation and quantification of these derivatives.
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  • 34
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxygen radicals ; Nucleotides ; Aldehydes
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    Topics: Chemistry and Pharmacology
    Notes: Summary The analysis of two metabolite groups, nucleotides and aldehydes, is necessary for assessment of oxygen radical metabolism during hypoxia and reoxygenation. Nucleotides and their derivatives were determined by HPLC using gradient elution with 10 mM NH4H2PO4 buffer containing 2 mM t-butylammoniumphosphate and acetonitrile. Aldehydes occuring after lipid peroxidation were analyzed by derivatisation to dinitrophenylhydrazones followed by TLC and HPLC separation with methanol/water on an ODS column.
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  • 35
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    Chromatographia 28 (1989), S. 209-211 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Triazine herbicides
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    Topics: Chemistry and Pharmacology
    Notes: Summary A number of 11 triazine herbicides and 7 of their corresponding metabolites were separated in a single HPLC run. The separation was achieved on a reversed-phase column using gradient elution with acetonitrile/buffer. Detection was by UV absorption at a wave-length of 220 nm.
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  • 36
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Polycyclic aromatic hydrocarbons ; Diode array and fluorescence detection
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    Topics: Chemistry and Pharmacology
    Notes: Summary Both the separation of polycyclic aromatic hydrocarbons (PAH's) on tailor made HPLC phases, and their chromatographic enrichment and quantitative determination are of great interest. Because of the generally low concentrations of PAH's in the environment, and the low limiting values in German legislation for drinking water, methods for selective enrichment and sensitive detection are indispensable. On account of their relatively high amounts in soil, the determination of PAH's is valuable for the assessment of the potential danger to ground water by waste materials. These requirements can be fulfilled by used of solid phase extraction on enrichment columns, and fluorescence or UV/VIS diode array detection. For the detection of PAH's in the picogram range, the wavelengths for excitation and emission were time programmed over the chromatogram. With this feature, it is possible to detect all the individual compounds at the highest sensitivity, over the entire analysis.
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  • 37
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    Chromatographia 28 (1989), S. 289-292 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micro-bore and capillary columns ; Gradient techniques
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    Topics: Chemistry and Pharmacology
    Notes: Summary A gradient delivery system for microbore and open tubular liquid chromatography is described. A gradient mixing vessel of 5–100μl, or 25–1000μl allows the generation of binary gradients with high reproducibility. The suitability of the system for short packed micro bore columns and open tubular columns is demonstrated.
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  • 38
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flecainide in plasma ; Fluorescence detection
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    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatographic method for the determination of flecainide in serum has been developed. The analysis is performed on a microparticulate silica column. The eluate is monitored by fluorescence detection at an excitation wavelength of 300nm and an emission wavelength of 370nm. No sources of interference were identified and a coefficient of variation of less than 8% was observed on repeated flecainide determinations. The method has a good reproducibility, specificity and accuracy, and can be applied in therapeutic drug monitoring of flecainide in patients.
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  • 39
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Coulometric electrochemical detection ; Methylnaltrexone ; Rat brain and serum analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and sensitive method is described for the determination of methylaltrexone, a quaternary narcotic antagonist, in discrete rat brain regions and serum. Separation and quantitation are performed by reversedphase high-performance liquid chromatography with coulometric electrochemical detection. Perchloric acid extracts of the brain tissue or serum were passed through a normal-phase solid-phase extraction CN column, and methylnaltreexone was subsequently eluted with a mixture of absolute ethanol and 25mM trifluoroacetic acid. Methylnaltrexone gave a linear response over the range of 12.5–100ng in 1.0ml for cerebellar homogenates and 25–200ng in 50μl for serum. The average betweenassay coefficients of variation for methylnaltrexone from 1.0ml of cerebellar homogenate and 50μl of serum were 5.2 and 3.6%, respectively, over the concentration range studied. The within-assay coefficients of variation at 12.5ng/ml cerebellar homogenate and 25ng/50μl for serum were 7.4 and 4.6%, respectively. Analytical recovery of methylanyltrexone, added to cerebellar homogenate and serum samples, were 85 and 89%, respectively. The method was applied to the analysis of methylnaltrexone in discrete rat brain regions and serum after intraperitoneal injection.
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  • 40
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    Chromatographia 28 (1989), S. 639-642 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns ; Split injection ; Sample tailing and cold trap effects
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    Topics: Chemistry and Pharmacology
    Notes: Summary Sample plug tailing together with a cold trap effect brings about discrimination against low boiling components at an initial column temperature above the boiling point of the solvent. In conventional split injection, this compensates for the opposite effects of such factors as the gas phase viscocity change and the pressure wave during the split period, and reasonable results are obtained. In stop-flow injection, however, since the influences of the opposite factors are diminished, the sample plug tailing and the cold trap effect may produce results showing lower than true concentrations for the low boiling components.
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  • 41
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    Chromatographia 28 (1989), S. 129-132 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carotenoids ; Paprika, Rose hips, Marigold
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the preparative HPLC of carotenoids and carotenoid esters using a self-packing axially-compressed column. The reversed-phase system used employs an RP-18 stationary phase and a mobile phase consisting of a mixture of petroleum spirit, acetonitrile, methanol and tetrahydrofuran. The method is demonstrated for paprika fruit, rose hips and marigold flowers.
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  • 42
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wheat proteins ; γ-gliadins ; Effect of pH on separation ; Effect of organic modifier on separation
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    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase, high-pressure liquid chromatography has been used to separate similar protein (γ-gliadin) components from 70% ethanol extracts of endosperm flour from two different accessions of the diploid wheatTriticum monococcum L. The effect of acetonitrile as the organic eluent was compared to acetonitrile: 2-propanol (3:1) at two different pH's. Conditions for maximum resolution of the γ-gliadin components were found to be at pH 7.2 with acetonitrile: 2-propanol (3:1) as the eluent. These conditions allowed the components to be obtained in sufficient purity for further charaterization.
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  • 43
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    Chromatographia 28 (1989), S. 313-314 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fused-silica columns ; Static coating ; Sealing method
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    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper a new sealing method for the static coating of capillary columns is described. When one end of the fully filled capillary was immersed into liquid nitrogen in a Dewar flask, the coating solution at this end would be frozen and became a temporary seal, and an air-free solvent/seal interface was obtained. No bumping has ever been found at the interface, even when butane was used as solvent. By applying this sealing method, several capillary columns, including some narrow bore capillary, had been successfully coated.
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  • 44
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand-exchange ; Preparative racemate resolution ; Amino-acids
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    Topics: Chemistry and Pharmacology
    Notes: Summary Preparative resolutions of racemic amino-acids by ligand-exchange chromatography are described. Base-line resolution of multigram quantities of many racemic solutes was obtained using very simple equipment (open tubular column).
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  • 45
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    Chromatographia 28 (1989), S. 354-358 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ternary mobile phases ; Solute retention model
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    Topics: Chemistry and Pharmacology
    Notes: Summary In our previous publications we have established a new physico-chemically grounded retention model valid for the adsorption and partition mechanism of retention using multicomponent mobile phases. Moreover, we have demonstrated its practical usefulness for predicting solute retention in several different chromatographic modes (i.e. in TLC, normal-phase and reversed-phase HPLC) employing binary mobile phases. In this paper we give an ultimate check to the physicochemical correctness of our new retention model, using it for the description of solute retention in reversedphase HPLC systems with ternary mobile phases of the B+AB1+AB2 type. The complexity of these mobile phases and of the possible intermolecular interactions among the consitituent solvents was supposed to rigidly scrutinize the premises of the assumed new approach. We have observed a good agreement between the experimental retention parameter for a number of solutes chromatographed with the use of two different mobile phases of the B+AB1+AB2 type, and the retention parameter calculated according to the assumed model. Therefore, we believe to have sufficiently tested our new approach and confirmed its physico-chemical correctness.
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  • 46
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Optical resolution ; Polymeric adsorbents ; Penicillin sulfoxide ; Substituent effect
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    Topics: Chemistry and Pharmacology
    Notes: Summary Fourteen new vinyl polymers carrying penicillin sulfoxide nucleus, poly (substituted-benzyl 1-oxo-6-metha-crylaminopenicillanate)s, were synthesized in order to investigate the influence of the substituents on the optical resolution capabilities. The resolution efficiency of the high-performance liquid chromatography columns comprising the obtained polymers were examined usingtrans-stilbene oxide and N-acetyl-1-phenethyl-amine. It was found that some columns resolved both racemates, some one, while the others did not separate either. A polymer which has 2,6-dichlorobenzyl moiety was found to resolve both racemates more effectively than the unsubstituted polymer.
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  • 47
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    Chromatographia 28 (1989), S. 465-468 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorinated phenols ; 4-Aminoantipyrine derivatives of phenols ; Metabolites of phenoxy alkanoic acid herbicides
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    Topics: Chemistry and Pharmacology
    Notes: Summary High performance liquid chromatography (HPLC) has been applied to the separation and determination of o-chlorophenol, 2,4-dichlorophenol, 3,4-dichlorophenol, 2,5-dichlorophenol, and 2,4,5-trichlorophenol in water samples after prior derivatization with 4-aminoantipyrine. These substances are the phenolic decomposition products of the phenoxy-alkanoic acid herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-dichlorophenoxybutyric acid (2,4-DB), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). An RP-C18 column was used, with gradient elution starting at 50/50 and changing to 70/30 methanol/water (v/v) after 24 min. Detection was carried out at 470 nm where the 4-aminoantipyrilquinonimine derivatives show maximum absorbance. The method was linear over a concentration range of 5–10,000 ppb phenol in the original water sample. By using an enrichment step a detection limit of 2 ppb phenol could be approached. The method was used to study the degree of degradation of the phenoxy acids to phenols under different conditions of temperature, pH, and UV irradiation.
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  • 48
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand exchange ; Chiral phase ; Optical resolution of 2-hydroxy acids
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    Topics: Chemistry and Pharmacology
    Notes: Summary Using an MCl GEL CRS10W column, which was packed with octadecyl silica (ODS) coated with N,N-dioctyl-L-alanine, optical resolution of 2-hydroxy acids was performed. The optical resolution of mandelic acid derivatives and C2 to C5 2-hydroxy acids was carried without any pretreatment. The MCl GEL CRS10W column could resolve amino acids and 2-hydroxy acids. For their selective detection, a post-column method was employed in which the specific color reaction of 2-hydroxy acids with iron(III) ion was utilized. For the analysis of foodstuffs, in which amino acids and 2-hydroxy acids often coexist, the present method was found to be effective in distinguishing between these enantiomers.
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  • 49
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    Chromatographia 28 (1989), S. 497-501 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Collagen metabolites ; Amino acid derivatives ; Glycosides
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    Topics: Chemistry and Pharmacology
    Notes: Summary Methods are described for the isolation of galactosyl hydroxylysine and glucosylgalactosyl hydroxylysine from collagen and for the quantitative analysis of these hydroxylysine glycosides. The isolation procedure, based upon gel filtration and preparative ionpaired reversed-phase high-performance liquid chromatography, is simple and rapid in comparison with existing methods, allowing the production of tens of milligrams of each glycoside in a single day. Quantitative analysis of the hydroxylysine glycosides is effected by reversed-phase high-performance liquid chromatography with precolumn derivatization (usingo-phthal-dialdehyde) and fluorescence detection.
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  • 50
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    Chromatographia 28 (1989), S. 502-504 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention variation ; Effect of sample composition on retention
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    Topics: Chemistry and Pharmacology
    Notes: Summary The variation of the retention index of a solute due to the presence of a closely neighboring peak is discussed. The neighboring peak is likely to modify the original stationary liquid by forming a temporary “mixed” stationary phase. The extent of the retention index variation is influenced by many experimental parameters and becomes pronounced when the stationary phase is overloaded by the neighboring peak and the film thickness of the stationary phase is not very large. However, the exact extent of this variation is rather unpredictable. The practical significance of this finding is also discussed.
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  • 51
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Optical resolution ; Polymeric adsorbents ; Penicillin sulfoxide ; Copolymerization
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    Topics: Chemistry and Pharmacology
    Notes: Summary A methacrylamide carrying penicillin sulfoxide skeleton, benzyl 1-oxo-6-methacrylaminopenicillanate, was copolymerized with methyl methacrylate. The optical resolution efficiency of the columns comprising the obtained copolymers was investigated using a high-performance liquid chromatography system. A copolymer incorporated by 27mol% of methyl methacrylate showed higher chirality recognition capability than the homopolymer, which suggests that the introduction of methyl methacrylate contributes to enriching desired penicillin sulfoxide alignment (i. e., tracticity) along the polymer main chain. An estimated penicillin monomer's number-average sequence length in the copolymer was 2.7.
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  • 52
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    Chromatographia 28 (1989), S. 519-522 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase chromatography ; Separation of metal acetylacetonates
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    Topics: Chemistry and Pharmacology
    Notes: Summary Using reversed-phase high-performance liquid chromatography acetylacetonate complexes with trivalent metals such as Al(III), Co(III), Cr(III) and Fe(III) have been examined in columns containing RP-2, RP-8 and RP-18 bonded phases. The mobile phase consisted of acetonitrile/water or methanol/water mixtures with various compositions. As shown the order of elution of the acetylacetonates depends on the type of the column packing and on the nature and concentration of the organic modifier in the mobile phase.
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  • 53
    ISSN: 1612-1112
    Keywords: Gas chromatography ; FAME fingerprinting ; Animal fats ; Transesterification
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    Topics: Chemistry and Pharmacology
    Notes: Summary The triglycerides of animal fats from milk, meat or cheese can also be characterized by the gaschromatographic pattern of the fatty acid methylesters (FAME) after conversion by an unsophisticated transesterification procedure. Even from the FAME pattern falsifications of commercial animal fats can be revealed by the fast separation of the FAME using a standard CW 20 M (polyethyleneglycol) capillary column. Characteristic patterns of FAME originating from different animals are shown. The patterns of the FAME from different races of the same animal are very similar, so that the characterisation according to the type of animal is not disturbed.
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  • 54
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Penstemide and serrulatoloside
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    Topics: Chemistry and Pharmacology
    Notes: Summary Penstemide and serrulatoloside, two iridoids of similar molecular structure, were separated by stepwise gradient TLC in a straight-phase systems (silica-ethyl acetate+isopropanol) and by HPLC in a reversed-phase system (ODS-silica — water+methanol).
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  • 55
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    Chromatographia 27 (1989), S. 71-76 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron-capture detector ; Constant-current mode ECD ; Non-linearity of ECD
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    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of the ionization source activity, sample input rate, electron capture rate constant, ventilation rate constant and baseline frequency on the linearity, detectability and sensitivity of the constant-current electron-capture detector (CC-ECD) were investigated. The proposed model representing an extension of the Wenthworth-Lovelock model proved to be useful in demonstrating that the CC-ECD can be highly nonlinear for strong electron capturers, at high ionization source activities, at a low ventilation rate constant and at low baseline frequencies. Optimization of the CC-ECD operation is possible by a reasonable adjustment of the studied parameters.
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  • 56
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Overpressured layer chromatography ; Furocoumarin isomers ; Preparative separation of plant extracts
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    Topics: Chemistry and Pharmacology
    Notes: Summary Preparative medium pressure liquid chromatography and semi-preparative high performance liquid chromatography on silica were employed for the isolation of eight furocoumarin isomers (iso-bergapten, angelicin, psoralen, bergapten, pimpinellin, sphondin, xanthotoxin and isopimpinellin). The conditions were transposed from analytical on-line overpressured layer chromatography and analytical high performance liquid chromatography, respectively. The retention data of the analytical on-line overpressured layer chromatographic separation and the preparative medium pressure liquid chromatographic isolation show a linear relationship. Using 15 μm TLC silica 60 as stationary phase a dry-packing procedure aas developed for labomatic medium pressure liquid chromatographic glass columns. The efficiency of the preparative separation techniques was demonstrated by the isolation of the investigated furocoumarins from Heraclei mantegazziani radix and from Pimpinellae radix (Balkan quality).
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  • 57
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Coke oven gas evolution ; On-line gas analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatograph will thermal conductivity detector (TCD) connected on line via a cleaning train to the semi-industrial scale Coke Oven Text Plant of the Spanish National Coal Institute (INCAR), has been used to control the evolution of the permanent gases during the coking process. The undesirable presence of oxygen in the coke oven gas can be detected with this system that will be applied to determine the end of the coking process by quantitative analysis of the gas evolved.
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  • 58
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    Chromatographia 27 (1989), S. 101-104 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bromo/iodosubstituted thyronines ; Mobile phase optimization ; Radioimmunoassay detection
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    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high performance liquid chromatographic method on C-18 bonded silica is described for the separation of trisubstituted iodo/bromothyronines, which exert thyroid hormone activity. The composition of the mobile phase has been systematically optimized resulting in a ternary mixture of methanol/acetonitrile/water acidified with trifluoroacetic acid. The applicability of ultraviolet absorption detection, amperometric detection and off-line radioimmunoassay was investigated. The latter method allows detection of the different iodo/bromothyronines down to 40–120 ng/l mobile phase; this sensitivity is high enough for application to thyroid hydrolysates in order to clarify the question as to whether bromine can substitute iodine in the biosynthesis of thyroid hormones.
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  • 59
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    Chromatographia 27 (1989), S. 113-117 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention contribution of nitrogen ; Effect on methylene and sulphur chains
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    Topics: Chemistry and Pharmacology
    Notes: Summary The reaction of secondary amines R2NH with disulfur dichloride S2Cl2 in dichloro methane yields mixtures of bis-dialkylamino polysulphides R2N−Sn−NR2 with sulphur chain lengths varying from ns=2 to 14. The S chains are believed to be non-branched. The compounds form homologous series in each of which sulphur atoms give a constant contribution to retention. The sulphur retention index depends slightly on the carbon number in the terminal alkyl groups R. The presence of nitrogen lowers retention. The index increment of N is ca. −160 units, which is distinctly less negative than values found in alkylamines.
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  • 60
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size-exclusion chromatography ; Fast atom bombardment-MS ; Peptic haemoglobin hydrolysate
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the ready identification of any peptide isolated from a complex peptic haemoglobin hydrolysate produced on the pilot-plant scale. A combination of size exclusion and reversed-phase, high-performance liquid chromatography have proved to be a useful strategy for fractionation of such a mixture. This technique enabled pure peptides from the total hydrolysate to be obtained. Amino acid analysis and fast atom bombardment mass spectrometry provided the accurate composition and molecular weight of any isolated peptide. Molecular weights are compared with those deduced from size-exclusion chromatography (SEC) and the usefulness of SEC is discussed. The procedure described in this study will be useful for acquiring a better knowledge of such an hydrolysate and could be extended to other crude protein digests.
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  • 61
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    Chromatographia 27 (1989), S. 182-184 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Micropacked columns ; Alkyl-modified silica ; Hydrocarbons
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    Topics: Chemistry and Pharmacology
    Notes: Summary Micropacked columns for liquid chromatography were evaluated for the gas chromatographic separation of hydrocarbons. A glass-lined stainless-steel tube of 30 cm×0.3 mm i.d., packed with 5-μm alkyl-modified silica, was employed as the separation column. The micropacked columns were successfully applied to the separation of components of a light oil and a kerosine.
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  • 62
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    Chromatographia 27 (1989), S. 205-208 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Kováts indices ; Numerical interpolation ; Dead time
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    Topics: Chemistry and Pharmacology
    Notes: Summary Comparison with normal procedures shows that numerical interpolation of the logarithms of gross retention times generates quite useful Kováts indices for gas chromatographic analysis. The dead time concept is not used in the interpolation.
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  • 63
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detector ; Amines ; Silages ; Feedstuffs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of the electrochemical detector (EC) in the high performance liquid chromatography (HPLC) of dansyl derivatives of biogenic amines is reported. Isocratic and gradient elution patterns of synthetic mixtures of putrescine, cadaverine, 1,6-diaminohexane, tryptamine, histamine, tyramine, spermine and spermidine on a reversed phase column are shown. Hydrodynamic voltammograms of standard compounds are presented. The detection limits of the EC are compared with those of ultraviolet and spectrofluorimetric detectors. A chromatographic profile of amines from the proteolytic catabolism of maize silage byClostridia is shown.
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  • 64
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase elution ; Silica and cyano columns ; Flavonoid compounds
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    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC retention data for a number of flavonoid compounds have been evaluated on normal phase silica and cyano colums according to the Soczewinski-Snyder (S.-S.) model. On the silica phase most of the flavones examined exhibited asymetrical peak shapes indicating strong and mixed retention mechanisms; on the cyano phase the intercept of the S.-S. relationship was independent of any hydroxy substitution pattern or of molecular planarity. A similar behaviour, but with different intercept values, was observed with coumarin and quinone compounds.
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  • 65
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    Chromatographia 27 (1989), S. 292-296 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Selenium(IV)-tellurium(IV) separation ; Flow-through coulometric detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of selenium and tellurium has been investigated with two different reversed-phase chromatographic methods, using P-350 (methyl-bi-isooctyl phosphate) and TBP (tributyl phosphate) as the stationary phases. HCl, HBr, NaCl and NaBr were employed as mobile phase components in both methods. The results suggested that the separation mechanism corresponds to the formation of TeCl (or TeBr) and P-350H (or TBPH) ion associate. A coulometric flow-through detector was applied to determine Se(IV) and Te(IV). Complete separation and quantitative determination of Se and Te could be achieved in 10 minutes.
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  • 66
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    Chromatographia 27 (1989), S. 325-327 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carotenoid ; Xanthophyll ; Broccoli ; Paprika
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the preparative HPLC of up to 50mg of carotenoid using a self-packing axially-compressed column. Oxygenated carotenoids, xanthophylls, are separated with silica as the stationary phase and acetone/petroleum ether as the mobile phase, while carotenes are separated using magnesium oxide/polyamide as the stationary phase and undiluted petroleum ether as the mobile phase.
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  • 67
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    Chromatographia 27 (1989), S. 340-342 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Evaporative light scattering detection ; α, ω-Dicarboxylic and hydroxycarboxylic acids ; Alkylglucosides and glycerides
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    Topics: Chemistry and Pharmacology
    Notes: Summary The advantages of an evaporative light scattering detector in HPLC are demonstrated using the separation of α, ω-dicarboxylic and hydroxycarboxylic acids, alkyl glucosides and mono-, di- and triglycerides as examples. By using this detector reversed phase as well as normal phase gradient HPLC becomes possible for substances with no UV absorption.
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  • 68
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    Chromatographia 27 (1989), S. 371-377 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alkyl-bonded silica gel ; Enthalpy ; Van der Waals volume
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    Topics: Chemistry and Pharmacology
    Notes: Summary Starting from silica gel with a purity of 99.999%, octadecyl-(ODS), octyl-(C8) and propyl-(C3) bonded silica gels were synthesized, and end-capped by trimethyl groups. The pore size was 150 Å and the specific surface area was 320 m2/g. The ODS and C8 silica gels were stable in both acidic and basic solutions. The selectivity of these bonded-silica gels was examined from the difference of the retention behavior of alkanes (Al−Al), alkylbenzenes (Ph−Al), alkylalcohols (Al−OH) and polyaromatic hydrocarbons (PAH) in aqueous acetonitrile. On these packings the log k′ values decreased in the order Al−Al〉Ph−Al〉PAH〉Al−OH. Furthermore, the chromatographic behavior of these compounds was measured on polymer-coated octadecyl-bonded silica gel (CAP) and octadecyl-bonded vinyl alcohol copolymer gel (ODP). The selectivity was verified from the value of R* of these compounds: $$R = R_v + R^* $$ where R is the retention time, and Rv is the retention time of an alkane having the same Van der Waals volume as the analyte. The R* values indicated that this ODS had more selectivity than C8 and C3, however R* on C8 showed a very good correlation with R* on C3. Their retention behavior on CAP was similar to that of ODS, however, their capacity ratios measured on CAP were smaller than those on ODS. The ODP has selectivity for the retention of aromatic compounds, because PAHs were retained strongly on this column.
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  • 69
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alternaria mycotoxins ; Food analysis ; Electrochemical detection
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    Topics: Chemistry and Pharmacology
    Notes: Summary The electroactivity of majorAlternaria mycotoxins has been explored in order to devise a liquid chromatographic-electrochemical detection (LC-EC) method for the determination of these toxic metabolites in fungal cultures and in naturally contaminated foodstuffs. Alternariol, alternariol methyl ether, altertoxin-I and altertoxin-II have been found to be electroactive and could be detected at sub-nanogram levels. Advantages and limitations of dual electrode (screen mode) coulometric detection and single electrode amperometric detection are presented and discussed. The feasibility of electrochemical detection in gradient elution liquid chromatography as well as its applicability to the analysis of contaminated foodstuffs is demonstrated.
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  • 70
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    Chromatographia 27 (1989), S. 431-435 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV diode array detection ; Electro chemical detection ; Herbicides
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    Topics: Chemistry and Pharmacology
    Notes: Summary An automated procedure is described for simultaneous UV detection at three different wavelengths and electro chemical detection in series of some residual herbicides. UV spectra of nine compounds of different compound groups are presented. Liquid-liquid extraction with dichloromethane and an enrichment of about one thousandfold has been used. Recovery rates after enrichment and detection limits of four s-triazine, three phenyl urea herbicides, metazachlore and metamitrone in river and drinking water are shown. It is concluded that the herbicides examined can be detected at levels between 10ng l−1 and 50ngl−1, without the necessity of derivatisation or clean-up processes.
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  • 71
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    Chromatographia 27 (1989), S. 257-263 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size exclusion ; Fractal dimension ; Retention model
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    Topics: Chemistry and Pharmacology
    Notes: Summary Some porous packings used in chromatography have been claimed to be fractals with a scale of sizes a〈l〈L, where a is a molecular size and L is the size of the largest pores. For a fractal porous packing, the excluded volume for molecules in solution in the vicinity of the packing surface is directly related to Df, the fractal dimension of the pore surface (2〈Df〈3). Since retention in size exclusion chromatography is itself directly related to this excluded volume, the fractal nature of the packing provides a model of retention in this technique. According to this model there is a linear relationship between log Rs and log(1-Kd), where Rs is the hydrodynamic radius of the solute macromolecules and Kd the distribution coefficient. The fractal dimension is derived from the slope of this plot. Size exclusion chromatographic retention data have been analyzed according to the model. It is found that some HPLC packings are fractals with fractal dimensions ranging from about 2.15 to 2.6, depending on the material. Such a large range of Df values indicates large variations in the selectivities and domains of applications of the different packings. For some classical gel filtration chromatographic gels, the fractal retention model does not seem to apply.
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  • 72
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Adsorption studies ; Clinoptilolite ; Zeolite
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    Topics: Chemistry and Pharmacology
    Notes: Summary Adsorption properties of NH4-clinoptilolite, thermally treated at 400, 550 and 650°C, were investigated by gas-solid chromatography. Adsorption of ten hydrocarbons, including aliphatic, alicyclic, chlorinated and aromatic compounds is discussed in the light of adsorbate-adsorbent interactions. The imporatant thermodynamic parameters of adsorption are determined. A detailed discussion is presented on the alteration of the surface properties of NH4-clinoptilolite caused by thermal treatment. Experimental data obtained show that NH4-clinoptilolite treated at 650°C can be successfully employed as a column packing in analytical gassolid chromatography.
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  • 73
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    Chromatographia 27 (1989), S. 436-440 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystal stationary phases ; PAH ; FAME ; Mesomorphic polysiloxane phases
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    Topics: Chemistry and Pharmacology
    Notes: Summary The gas-chromatographic properties of two mesomorphic polysiloxane (MEPSIL) stationary phases, one smectic (SB) and the other nematic (N), were investigated. The retention indices and separation factors (relative retentions), α, of several pairs of polycyclic aromatic hydrocarbon (PAH) and fatty acid methyl ester (FAME) isomer solutes were used to gauge differences in the selectivity provided by each. The heats of solution of the PAH showed that the smectic MEPSIL is more selective for solutes with different length-to-breadth ratios. Also, five peaks were resolved for sixcis andtrans octadecenoic FAME isomers with this solvent. The nematic MEPSIL, on the other hand, was found to be more useful at higher temperatures because of its higher clearing point. In addition, solute capacity factors were smaller than those observed with the smectic MEPSIL, as evidenced by lower retention indices. The former was therefore more useful for the analysis of high molecular-weight PAH.
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  • 74
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micro-columns ; Flow rate and temperature programming ; PTH amino acid derivatives
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    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of phenylthiohydantoin (PTH) amino acid derivatives by flow rate and temperature programming in reversed-phase micro-column liquid chromatography (LC) has been investigated. For both programming modes a microcomputer-assisted retention prediction system (REPRES) was constructed. The performance of this system has been evaluated by comparing actually measured retention data to those predicted. Excellent agreements between those data were found. It is clearly indicated that simultaneous flow rate and temperature programming can improve the separation of PTH-amino acids in reduced analysis time.
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  • 75
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    Chromatographia 28 (1989), S. 89-91 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrophoresis ; Comparison of HPLC and electrophoresis ; Proteins, peptides and amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Protein structure analysis is an indispensible tool in modern biological research. However, the isolation of a protein or the separation of peptides in a form suitable for sequence analysis is a considerable technical challenge. The two predominant separation methods in protein biochemistry are chromatography and electrophoresis. In this paper the position, advantaged and disadvantages of both HPLC and electrophoresis for the separation of amino acids, peptides and proteins in protein structure analysis are discussed.
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  • 76
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Colloidal stationary phases ; Liquid crystals as stationary phases
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    Topics: Chemistry and Pharmacology
    Notes: Summary Colloid systems consisting of the nematic liquid crystals p,p′-azoxyphenetol and p,p′-methoxyethoxyazoxybenzene and high-disperse mineral particles (aerosil, carbon black) are proposed to be used as stationary phases in gas chromatography. The dependence of the retention of normal paraffins, Rohrschneider and McReynolds test solutes (benzene, ethanol, methyl ethyl ketone, nitromethane, pyridine, butanol-1, 2-pentanone, and nitropropane) on the composition of the colloid systems was investigated. The investigated colloid sorbents including liquid crystals retain their selectivity for meta/para isomers up to 50% of the aerosil content and practically at all studied carbon black concentrations.
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  • 77
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    Chromatographia 28 (1989), S. 565-568 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; New bonded phases ; Alumina ; Protein separation
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    Topics: Chemistry and Pharmacology
    Notes: Summary Several reactions are tested for the chemical modification of alumina. These include the following: chlorination of the surface hydroxyls followed by reaction with an organolithium compound; chlorination of the surface hydroxyls followed by reaction with a Grignard reagent; chlorination of the surface hydroxyls followed by reaction with an amine; chlorination of the surface hydroxyls followed by reaction with an alcohol; direct reaction of the alumina with an organochloroalane and direct reaction of the alumina with an alcohol. Only the first reaction gave a product which contained enough bonded organic material to be easily detected by FTIR. Preliminary stability tests show that the product of the first reaction retains the bonded organic material when exposed to nonpolar and polar organic solvents as well as aqueous solutions of pH 1.0, 7.0 and 12.0. Chromatographic testing establishes reversed-phase behavior for alkylarylketones as solutes and the bonded phase displays good biocompatibility for a series of protein standards.
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  • 78
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine phosphates ; Adenosine phosphate degradation products ; Innervated frog muscle
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    Topics: Chemistry and Pharmacology
    Notes: Summary Adenosine mono-, di- and triphosphates, inosine monophosphates, adenosine, inosine and hypoxanthine were separated in a single run by high-performance liquid chromatography with UV detection. AC-18 reversephase column was used. An isocratic elution with 100mM phosphate buffer (KH2PO4) pH6.5 and 1.2% methanol, followed by a 5 minute linear gradient up to 15% methanol after the 10th minute was performed during each run with a flow rate of 1.25ml/min. The time required for each analysis was 25 minutes. The detection limit for each substance ranged from 3 to 5 pmol. All the substances under study were detected in the incubation medium when adenosine triphosphate was exogenously applied to the innervated frog sartorius muscle.
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  • 79
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chlorinated methanes ; Activated charcoal sampling ; Pollution
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    Topics: Chemistry and Pharmacology
    Notes: Summary A sampling method using activated charcoal, followed by percolation with ethanol and FID or ECD chromatographic analysis, depending on the concentrations to be monitored, makes it possible to evaluate concentrations of methylene chloride between 5 and 1000mg m−3, chloroform between 0.1 and 2000mg m−3, and carbon tetrachloride between 0.015 and 1000mg m−3.
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  • 80
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    Chromatographia 28 (1989), S. 139-142 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silica surface ; Silanols ; Strongly interacting sites
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    Topics: Chemistry and Pharmacology
    Notes: Summary The paper describes how the method of gas-phase titration of the strongest adsorption sites can be utilized to calculate a relative strength of interaction of the sites with chromatographic solutes. An excellent correlation with earlier, theoretical predictions of Giddings is noted. Significant influence of the sites on the width of a chromatographic band is observed when the interactions are an order of magnitude stronger than those of normal sites.
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  • 81
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular interactions ; Association effects ; Analyte solvation
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    Topics: Chemistry and Pharmacology
    Notes: Summary The linear Jaroniec equation has been utilized for the description of chromatographic systems in which the test substance molecule is solvated by the solvent molecules. A possibility of the formation of multimolecular solvates in the bulk phase has been confirmed. The measurements were made using liquid adsorption chromatography with ternary mobile phase.
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  • 82
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    Chromatographia 28 (1989), S. 167-169 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Determination of monomer in polymers ; Sealed glass capillary sampling
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    Topics: Chemistry and Pharmacology
    Notes: Summary Residual styrene in polystyrene and free phenol in phenolic plywood adhesive have been determined by sealing samples in glass capillary tubes. To prevent loss of sample the ends of the capillary tubes were sealed with a kind of putty made of anhydrous calcium sulfare, calcium carbonate and a small quantity of phenylmethylsilicone fluid. No volatile compounds were released from this sealing material when the capillary tubes were placed in a quartz vaporising furnace at temperatures up to 300°C.
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  • 83
    ISSN: 1612-1112
    Keywords: Gas chromatography ; GC/MS and headspace GC ; Elastomeric stoppers for injectables ; Trace hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Elastomeric stoppers for injectables have been surveyed by means of GC/MS screening. Residual contamination by hexanes (2-methylpentane, 3-methylpentane, n-hexane, methylcyclopentane, cyclohexane) toluene and xylenes occurred in all the samples tested. A headspace GC purity test is suggested, by using these residual chemicals as purity indexes.
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  • 84
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separations ; Trypsin on silica ; Amino acids
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new HPLC stationary phase was synthesized by the covalent immobilization of the enzyme trypsin (TRYP) on silica. The hydrolytic activity of the immobilized enzyme was 72% of the activity of an equivalent molar amount of free TRYP. The initial chromatographic studies indicate that this phase can be used for chiral separations of enantiomeric O- and N,O-derivatized amino acids which are natural substrates on TRYP and that the stereochemical resolutions are a result of the activity of the enzyme.
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  • 85
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    Chromatographia 28 (1989), S. 574-578 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases ; End-capping ; Destructive effects on bonded phases
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    Topics: Chemistry and Pharmacology
    Notes: Summary Hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMS) have been used as a secondary deactivation (end-capping) reagents for packing materials for RP HPLC. Three types of chemically bonded phases (CBP) with different structures and different coverage densities were used. The destructive effects of HMDS on the coverage density of chemically bonded C18 and C8 phases is discussed.
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  • 86
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Optimization of gas-solid separations ; Plate height equation ; Computer mapping procedure
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    Topics: Chemistry and Pharmacology
    Notes: Summary This paper proposes an optimization model for gas-solid chromatographic separations in a non-linear programming form and an approximate equation of the plate height for the model. A computer-modified mapping procedure is also described for searching the optimum separation conditions. Just five experiments and about 20 minutes of the computer time are needed to establish the optima of column temperature and of the carrier gas linear velocity. The relative deviation between the predicted and the experimental values was found to be within 20% for the plate heights, and within 1.5% for the retention times.
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  • 87
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cellulose acetate ; Acetyl content ; Temperature effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Cellulose and cellulose mono-, di-, and triacetate were used as stationary phases for liquid chromatography with water as a mobile phase, and the retention behavior of alcohols, ethers, ketones, and chlorides was examined. For cellulose acetate columns, the logarithm of the specific retention volume, (logV g * ), correlated linearly with the logarithm of partition coefficient between 1-octanol and water (log Ko/w), for each homologous group, but all solutes were unretained on cellulose columns. With the exception of chlorides, the intercept values of the log V g * –log Ko/w regression lines increased significantly with increase of acetyl content of cellulose acetates, but the slopes of the regression lines changed little. This suggests that hydrophobic interaction between the acetyl groups of cellulose acetates and the alkyl chains of the solutes is the dominant factor in the retention. The capacity factors for 1-alcohols with cellulos diacetate column indicated a maximum at a column temperature of about 40°C. This unique retention behavior was assumed to be caused by small structural change of the cellulose acetate polymer, because this temperature effect on the retention corresponded with effects observed by differential scanning calorimetry (DSC).
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  • 88
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    Chromatographia 28 (1989), S. 161-166 
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Column liquid chromatography ; Micropreparative separations ; Furocoumarins
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    Topics: Chemistry and Pharmacology
    Notes: Summary Furocoumarins from extracts ofHeracleum genus fruits were separated using normal and reversed phase TLC and HPLC and isolated in the milligram scale using overloaded systems of column chromatography. Binary or ternary solvents containing a polar modifier (methanol, diisopropyl ether or acetonitrile) were used as the mobile phases.
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  • 89
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion-exchange ; Mobile phase optimisation ; Egg-white proteins
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    Topics: Chemistry and Pharmacology
    Notes: Summary Factors influencing the capacity of Whatman QA52 anion-exchange cellulose for hen egg-white proteins have been investigated. While simply increasing the concentration of protein in the feedstock increases the loading there is a concomitant reduction in binding efficiency in a single pass through the column. Substitution of buffer by water in the mobile phase during sample preparation, thereby reducing the ionic strength of the feedstock, had the effect of significantly increasing protein capacity whilst improving binding efficiency. During column loading large changes in pH of the mobile phase were observed although this had no apparent effect on the chromatography for this system.
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  • 90
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    Chromatographia 28 (1989), S. 193-196 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phases ; Immobilized enzymes ; Racemic resolution of amino acid esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Racemic resolution of aromatic and aliphatic amino acid esters into L-amino acid and D-amino acid ester via LC and HPLC is achieved by using enzyme reactors as chromatographic columns. For this purpose α-chymotrypsin and trypsin are immobilized on Eupergit C, Sepharose 4B and Lichrosorb-Diol.
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  • 91
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Renewal theory ; Monte-Carlo simulation ; Prediction of retention and peak widths
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for prediction of gas chromatographic retention times and peak half widths is based on the renewal theory. The only requirements are the heats of vaporization of the compounds to be separated and one calibration measurement. With this data, retention times and peak half widths can be predicted for isothermal as well as temperature-programmed gas chromatography. For the separation of non-polar substances on non-polar stationary phases the prediction error for retention times is approx. 1–2%. First simulations of polar molecules and polar stationary phases indicate that this method is also applicable in these cases but some extension will be required.
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  • 92
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bonded stationary phases ; Evaluation of the hydrophobicity of sorbents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The energy of interaction (∈0) between the methylene group and the surface of a sorbent is proposed for use in the quantitative evaluation of the hydrophobicity of a sorbent. A method was developed to determine the ∈0 parameter from chromatographic measurements using the investigated sorbent as the stationary phase and linear methylene-containing homologous series, e.g., alkanols, amino-alkanes, etc., as the test compounds. The effectiveness of this method is demonstrated by using, as examples, a series of bonded stationary phases and a series of cross-linked copolymeric sorbents differing in the concentration of the hydrophobic groups. The proposed method is compared with the Martin rule used extensively in the chromatography of oligomers.
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  • 93
    ISSN: 1612-1112
    Keywords: Thin-layer chromatography ; Column liquid chromatography ; Mobile phase optimization ; HPTLC transposition to HPLC
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    Topics: Chemistry and Pharmacology
    Notes: Summary A computer-assisted method is presented for mobile phase selection for the optimal separation of pesticides by HPTLC and HPLC. The system is based on a plot of solute retention value and separation criterion vs. binary mobile phase composition for graphic optimization. The result of HPTLC can be transposed to HPLC for optimal separation. The transposition equation is given.
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  • 94
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    Chromatographia 28 (1989), S. 311-312 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flavonoid glycosides ; Betula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The main flavonoid glycosides ofBetulae folium extracts (quercetin-3-glucuronide, myricetin-3-galactoside, hyperosid, quercetin-3-arabinoside and quercetin-3-rhamnoside) have been separated by isocratic elution on a C18 Aquapore RP-300 column. Elution was performed with 17% isopropanol at pH 6.2 confirming the validity of this eluent for the analysis of the flavonoid glycosides.
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  • 95
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phase ; Resolution of amino acid derivatives ; Enantioseparation by HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chiral stationary phase for the separation of some D-and L-amino acid derivatives using a new resolving agent is described. The enantiomeric resolution was accomplished by normal phase high-performance liquid chromatography. The support was easily prepared by coating an epoxy polymer of L-valinamide on aminopropylsilanized macroporous silica. The influence of subambient temperatures on the enantioselectivity was also examined.
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  • 96
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral recognition process ; Enantiomeric elution order ; Mobile phase modifiers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three enantiomeric solutes, a sulphoxide, a piperidine derivative and a methyl ester have been chromatographed on an HPLC chiral stationary phase (CSP) based upon cellulose-tribenzoate (Chiralcel OB-CSP). The mobile phases used in the study were composed of hexane modified with homologous series of primary, secondary and cyclic alcohols. Interesting reversals in enantiomeric elution order have been observed for 2-phenoxypropanoic acid methyl ester associated with changes in chain length or ring size of the alcohol mobile phase modifier. The results of the study suggest that at least two chiral recognition mechanisms operate on the OB-CSP and point out the importance of acquiring elution order data in all studies involving chiral stationary phases.
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  • 97
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Prediction of retention times ; Gradient elution ; Substituted quinolines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chromatographic model able to predict, from experimental isocratic data, retention times of solutes under gradient conditions has been proposed previously. The prediction was shown to be totally independent of the chemical properties of both solutes and eluents. In order to further check the general validity of the theory, the model has now been applied to a nonhomologous set of compounds, namely a range of substituted quinolines (methyl-, hydroxy- and amino-) and several different stationary phases. Results show a dependence on the stationary phase and, to a lesser extent, on the chemical structure of the solutes. The possible sources of errors are discussed. The generality of the method holds, within acceptable limits, if predictions concern the same type of stationary phase.
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  • 98
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Microwave plasma detector ; Thiophenes ; Shale oil distillates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A series of alkylthiophenes and dimethyl disulfide were tentatively identified in an oil shale retort gas condensate from a 6-kg bench-scale retort using gas chromatography with a microwave-induced helium plasma detector (GC-MIP). The sulfur species were present in concentrations ranging from 1.5 to 10.7 mol ppm in the undiluted offgas. The GC-MIP technique was successful in selectively detecting the sulfur components in the complex mixture. Quantitation was simplified relative to GC with flame-photometric detection because of the absence of quenching or other interference problems at the concentrations studied. Attempts to determine stoichiometry of the sulfur components by comparison of carbon, hydrogen, and sulfur ratios with those of standards were unsuccessful because of the complexity of the carbon and hydrogen chromatograms.
    Type of Medium: Electronic Resource
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  • 99
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Air pollutants ; Adsorbent enrichment ; Thermal desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new automatic method is described for quantitative determination of some light C2–C4 hydrocarbons in urban air: ethene, ethyne, propane, propene, butane and iso-butane. This method is based on an enrichment step at room temperature using a solid sorbent and subsequent thermal desorption for gas chromatographic separation and FID detection. The instrument is built up of a small commercial gas chromatograph and a laboratory-made trap and desorption unit. The sampling parameters, sample volume, concentration and humidity of air have been investigated.
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  • 100
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 27 (1989), S. 596-600 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass spectrometry ; Azines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We have studied the gas chromatographic behaviour of several 3-methyl-2-benzothiazolone-azines. In HPLC analysis all the unsymmetrical azines show double peaks, whereas in HRGC analysis only some of these compounds show the two peaks corresponding to the Z (syn) and E (anti) isomers. By means GC/MS analysis the mass spectrum of each azine was recorded. We have assigned the E and Z configurations to the first and second gas chromtographic peaks on the basis of the ratio between the relative abundances of the two most significant framment ions at m/z 163 and 164.
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