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  • Liquid chromatography  (26)
  • Springer  (26)
  • American Geophysical Union (AGU)
  • Annual Reviews
  • 1990-1994
  • 1980-1984  (26)
  • 1982  (26)
Collection
Publisher
  • Springer  (26)
  • American Geophysical Union (AGU)
  • Annual Reviews
  • Wiley-Blackwell  (6)
Years
  • 1990-1994
  • 1980-1984  (26)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 595-598 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; High-speed liquid chromatography ; Small-particle LC columns ; Injector bypass ; Column lifetime in LC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In the case of liquid chromatography columns packed with small (3–5 μm) particles and utilized at relatively high flow rates, pressure pulses associated with the sample injection process (caused by a short-duration interruption in mobile phase flow to the column during injection) may result in a reduction of column lifetime. This detrimental effect can be eliminated by the utilization of specially constructed sample injection valves incorporating properly desinged bypass loops. The paper investigates in detail the effect of pressure pulses, describes the criteria and performance of the bypass systems, and documents column life time and performance.
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  • 2
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    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 83-85 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Tricyclic antidepressants ; Solid phase extraction ; Serum ; Clinical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Five common tricyclic antidepressants are separated on a silica column using an aqueous eluent. The tricyclics are concentrated from serum using an adsorption procedure on a solid phase Sep PakTM C18 cartridge. The method appears to be adequate for monitoring therapeutic levels of these drugs.
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  • 3
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Complex solvent mixtures ; Optimization of solvent composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Four different methods of calculation of retention in ternary mobile phases were compared and it was found that the simple calculation based only on two values of the capacity factors (one for each binary system that composes the ternary mobile phase) provides the accuracy of prediction that is, at least, comparable to the other methods of calculation that require a large number of preliminary experiments. The deviations from ideal behaviour in ternary solvent mixtures are discussed; some sources of errors can be avoided, at least partially, using binary systems of adequate compositions for preparation of ternary mobile phases. Several examples show the comparison of calculated and experimental selectivities in ternary solvent systems. A simple calculation can be used for rapid selection of an adequate ternary (or more complex) mobile phase, if it is necessary to achieve the separation of a given sample mixture.
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  • 4
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Reverse-phase ; 3 μm packing materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of high-performance liquid chromatography columns packed with 5 μm and 3 μm reverse-phase octadecylsilane packing materials has been evaluated using four test mixtures. Both stopped flow and valve injection have been used and typical efficiencies are given.
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  • 5
    ISSN: 1612-1112
    Keywords: Phosphorescence, room-temperature ; Detection, continuous flow ; Liquid chromatography ; Halogenated componds ; Dibenzofurans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is shown that sensitized room-temperature phosphorescence in liquid solutions can be successfully applied as a detection method in continuous flow and chromatographic systems. The limits of detection for a series of halogenated naphthalenes and biphenyls obtained by plug injection are roughly the same as those in batch experiments — in the subnanogram region. Liquid chromatograms of mixtures of PCBs, PCNs and polychlorodibenzofurans are given.
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  • 6
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Chlorophenols in water ; Preconcentration ; Post-column photochemical dechlorination ; Electrochemical, UV and fluorescence detection ; Column switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A specific HPLC method has been developed for the trace analysis of lower chlorinated aromatic compounds. The method consists of an on-line preconcentration and a post-column reaction step. On-line preconcentration of mono- and dichlorophenols from aqueous samples has been performed using PRP1, a divinylbenzene-styrene copolymeric sorbent as packing material for both pre-and analytical column. Enrichment factors of over 300 were obtained compared to regular (100 μl) loop injections, even for the highly polar monochlorophenols. After reversed-phase separation, post-column photochemical dechlorination is carried out directly in the eluent stream, using a photochemical reactor. Upon dechlorination, fluorescent products are formed, which can be detected selectively. The resulting fluorescence signal shows a linear response to the quantity of solute present over 2 to 3 orders of magnitude (correlation coefficients: 0.990–0.98). For the mono- and dichlorophenols, the detection limit of the photoconversion method is in the lower nanogram range. The method is especially suitable for the analysis of complex matrices such as effluent water samples or biological fluids containing traces of the polar chloroaromatic compounds together with large amounts of other constituents, which interfere when using more general methods of detection like UV absorption. The potential of this technique for automation has been demonstrated by using a microprocessor-controlled column switching unit.
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  • 7
    Electronic Resource
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    Springer
    Chromatographia 15 (1982), S. 437-444 
    ISSN: 1612-1112
    Keywords: Detection ; Liquid chromatography ; Reversed phase ; Ion-pairing probes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Compounds without own detector response can be detected and quantified by a UV-absorbing or fluorescent, ion-pairing probe in reversed-phase liquid-solid systems. Charged as well as uncharged samples give response by affecting the distribution of the probe between the phases. The probe is usually a hydrophobic organic ion. It is included in the mobile phase, which also contains a counter ion and an ion of the same charge as the probe, both fairly hydrophilic. The choice of properties and concentrations of the hydrophilic ions is essential for the response since too low and too high distribution of the mobile phase ions to the adsorbent will make the system insensitive. It is with UV-absorbing probes possible to get a response corresponding to a molar absorptivity of more than 3000 for ionic samples. Fluorescent probes have given 3–5 times higher sensitivity. Uncharged compounds give as a rule lower response. A combination of two UV-absorbing probes with different charge gives a considerable improvement of the response for samples with low retention. A simplified theoretical model for the detector response is suggested on the basis of detailed studies of the concentration changes in the eluted mobile phase.
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  • 8
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Photochemical reaction detection ; Chemical post-column reduction ; Fluorimetric detection ; Air segmented flow systems ; Non-aqueous reversed-phase chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new photochemical reaction method for the on-line fluorimetric detection of natural vitamin K homologs was developed. In addition to its high sensitivity, the method features an interesting selectivity for the determination of these compounds in a complex matrix such as human serum. The formation of different photolysis products as a function of reaction conditions, and the optimalisation of a segmented flow reaction system will be discussed. The results indicate that the method is 4 times more sensitive than UV detection, and at least as selective as fluorescence detection after post-column chemical reduction.
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  • 9
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    Springer
    Chromatographia 15 (1982), S. 476-478 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Mass detector ; Carbohydrates ; Lipids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The mass detector was investigated as an alternative to RI detection for carbohydrate and lipid analyses with high pressure liquid chromatography. The instrument was found to be more sensitive than most RI detectors and, as gradient elution could also be carried out, the resulting chromatograms showed improved resolution.
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  • 10
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Nucleobases ; Nucleosides ; Silica gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of nucleobases and nucleosides on unmodified silica with dichloromethane-methanol-water mixtures has been systematically investigated. The degree and order of retention can be varied over a wide range by changing the pH, the type and concentration of the acidic additives and by the methanol and water content of the mobile phase. The retention process cannot be considered as simple adsorption but rather as a very complex mixed distribution process of adsorption and absorption including the involvement of ion-pair formation. Further data on the effect of the type of silica (source of supply) on retention behaviour, column efficiency and column reproducibility are reported. The practical application of unmodified silica for the separation of nucleobases and nucleosides is demonstrated by the analysis of a hydrolysate of calf thymus DNA.
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  • 11
    Electronic Resource
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    Springer
    Chromatographia 15 (1982), S. 403-408 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Reaction detector ; Colorimetric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reaction detector with non-segmented flow in open tubes as reaction track is described. To minimize peak broadening the open tubes are arranged in a three dimensional coiled structure by knitting. At low volume flow rates the h-values in these open tubes are independent of flow rate and are significantly lower than predicted by theory. The applicability of this reactor for classical colorimetric detection with corrosive reagents is shown.
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  • 12
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Ultra-violet detection ; Temperature effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper is concerned with our investigation into the effects of temperature on the liquid chromatography absorbance baseline. Measurements were made to quantify the effects in terms of wavelength and solvents. Five solvents commonly used in HPLC were investigated, methanol, propanol, hexane, heptane and acetonitrile. The alcoholic solvents were found to have a high absorbance sensitivity to temperature at wavelengths around their ‘UV cut off’ points. Possible mechanisms for this effect are discussed and include solvent impurity, density changes and inter-molecular bonding.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 16 (1982), S. 18-25 
    ISSN: 1612-1112
    Keywords: Gaschromatography ; Liquid chromatography ; Open tubular columns ; Capillary columns ; History of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper presents an overview of the evolution of open tubular (capillary) columns introduced 25 years ago by M.J.E. Golay. This evolution is divided into five stages: the formulation of the theory and the basic work laying down the foundations for future work; learning the influence of the variables on column performance; development of columns with increased surface area; development of glass and fused-silica columns; and, finally, the introduction of open tubular columns in liquid chromatography. In each stage, the pioneering activities are summarized and the most important references given.
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  • 14
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Derivatization with NBD-F ; Amino acids, biogenic amines ; Blood analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The reaction of a newly developed fluoregenic reagent, 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole(NBD-F), with amino acids and biogenic amines was investigated. NBD-F was reactive to both primary and secondary amines including amino acids and biogenic amines such as catecholamines. The amino acids were reacted with the reagent, separated by high-performance liquid chromatography on μ-Bondapak C18 and detected at 10 to 100 fmol level. A few μg of protein hydrolysates, rabbit pyruvate kinase M1, rabbit aldolase A and papain, were adequate for the amino acids quantitation. An automatic amino acid analyzer with fluorometric detection by the post-column derivatization with NBD-F enabled the amino acid profile analysis in blood samples present in a paper disc of 3 mm diameter.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 16 (1982), S. 216-218 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Size exclusion ; Biological extracts ; Allergens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Extracts of insect, mite, fungal and mammalian origin, known to provoke an allergic response in man, have been examined and fractionated by high-performance size exclusion chromatography. The mild conditions employed for separation have permitted direct immunological assessment of the fractions obtained, and recognition of the biologically important components. These are being isolated for further study. This chromatographic procedure has proved to be of value for assessing different extracts from the same source material as potential reference preparations. It can also be employed as a sensitive method for identification of extracts derived from a variety of sources.
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  • 16
    Electronic Resource
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    Springer
    Chromatographia 16 (1982), S. 224-227 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Chiral bonded phases ; Aminoacid racement resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary N-Protected aminoacids have been chemically bonded to aminopropylated silica gel, and the resulting chiral phases have been applied to the LG resolution of racemic mixtures of polar compounds. Best results were obtained with surfacebound N-formyl-isoleucine and N-formylvaline, with which baseline resolutions of a range of aminoacid and aminoalcohol derivatives were achieved.
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  • 17
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    Chromatographia 16 (1982), S. 237-241 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Electron capture detection ; Improved interface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved interface for the coupling of a liquid chromatograph (LC) and an electron-capture detector (ECD) allows the use of the LC-ECD combination for the determination of various types of chlorinated aromatic compounds. The addition of up to 6% of dioxan to the hexane used as mobile phase can be tolerated without serious deterioration of detector performance. Derivatization of polar compounds such as anilines, phenylurea herbicides, chlorophenols and hydroxylated polychlorobiphenyls with fluorine-and non-fluorine-containing acid anhydrides is a useful tool to extend the application range of LC-ECD. As an example, the analysis of a spiked soil sample is discussed.
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  • 18
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    Springer
    Chromatographia 16 (1982), S. 265-266 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Short micro bore columns ; Small volume electrochemical detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A flow-through two electrode wall-jet cell with a platinum measuring electrode and a cell volume of 20 nl has been designed and evaluated. It has been used to detect phenols by reversed phase liquid chromatography using short micro bore columns. The linear dynamic range between the measured current and the concentration is greater than 103 (1.5×10−7−5×10−4 mol/l) and the minimum analyzable amount was found to be 10 pg for pyrocatechol. A negligible broadening in the detector permits the use of micro columns down to 0.5 mm internal diameter, packed with 5 μm particles, without any substantial distortion of eluted zones.
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  • 19
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Chemically bonded silica ; Hydrolytically stable ; Metal complexing ligands ; Amino acid separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A silica of 14 nm pore size was reacted according to two procedures with the following silanes: γ-aminopropyltriethoxysilane (1), N-aminoethyl-N′-aminopropyltrimethoxysilane (2), N-aminoethyl-N′-aminoethyl-N″-aminopropyltrimethoxysilane (3), N-(3-triethoxysilanepropyl)-N, N-diacetic dimethylester (4), N-(3-trisodiumsilanolatepropyl)-N, N-diacetic acid disodium salt (5) and N-(3-trisodiumsilanolatepropyl)-ethylenediamine-N, N′, N′-triacetic acid trisodium salt (6). The reaction of silanes 1–4 with the silica was carried out under anhydrous conditions (procedure A). Silanes 1–6 were subjected to surface modification under essentially hydrous conditions applying a two-step procedure (procedure B). Procedure B is much simpler to perform and allows binding of high and definite amounts of silane onto the surface. Complexation of all bonded phases with Cu2+ was examined by measuring the sorption isotherms at constant pH. The pH-dependence of Cu2+ uptake at constant Cu2+ concentration was evaluated. Tests on the chemical and chromatographic stability of the packings showed that only the silicas with bonded iminodiacetate and ethylenediaminetriacetate groups remain hydrolytically stable. Retention of aliphatic and α-amino acids on these two packings was found to be mainly controlled by the pH and the ionic strength of the eluent.
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  • 20
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Multiphase eluents ; Biopolymers ; Microorganisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A novel form of liquid chromatography is described which involves the use of multiphase eluents, such as emulsions, for the separation of biopolymers and certain microorganisms.
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  • 21
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    Chromatographia 16 (1982), S. 368-371 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Hydrated silica gel ; Nonpolar and polar eluents ; Elevated column temperatures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of nonpolar (hexane, decane, benzene) and polar (water, isopropanol, water+isopropanol) eluents on separation of aromatic hydrocarbons and their derivatives in liquid-adsorption chromatography on hydroxylated silica gel columns has been studied. The work has revealed that the traditional application areas of hydroxylated silica gel in liquid chromatography may be extended. In particular it has been shown that, first, polar compounds may be separated on hydroxylated silica gel with nonpolar eluents at high temperatures (100–150°C) and that polar and nonpolar compounds may be separated using pure water as eluent. The effect of adsorbed moisture on retention behaviour of silica gel with nonpolar eluents has also been investigated.
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  • 22
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Terbium determination ; Trace element analysis ; Gadolinium oxide sulphide ; Luminescent phosphors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A detailed study of isocratic and gradient elution separations of lanthanides has been carried out. Analyses of industrially and scientifically interesting products such as luminescent phosphors have been carried out by gradient elution with DL-2-hydroxyisobutyric acid. The determination of small amounts of terbium in gadolinium oxide sulphide phosphors is described in which an HCl solution was eluted through a stainless steel column packed with microparticulate silica, with bonded cation-exchange groups. Complete separation of gadolinium and terbium is achieved. Detection is with a variable wavelength detector following post-column complex formation with 4-(2-pyridylazo)-resorcinol monosodium salt. Results obtained on test solutions show good reproducibility and sensitivity and the method may be considered sufficiently reliable to be used in routine quality control procedures.
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  • 23
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Carbohydrates ; Bonded-phase columns ; Silica gel modified with amino groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For the separation of carbohydrates by liquid chromatography, utilizing the intermolecular interaction with amino groups on the surface of the adsorbent, two types of adsorbents were used: silica gel modified by adding to the eluent a diamine, and a chemically bonded phase prepared by the reaction of γ-aminopropyl triethoxy silane with silica gel. Mono- di- and trisaccharides could be separated on silica gel modified by the adsorption of piperazin and ethylene diamine from the eluent. The separation capacity of columns packed with silica gel with bonded NH2 groups and with silica gel having diamines adsorbed on its surface is similar. The retention volumes of 15 carbohydrates were measured on columns containing silica gel with hydroxylated surface and on silica gel modified with piperazin from the eluent consisting of acetone-water. Comparison of acetone-water and acetonitrile-water as the eluent showed that the former is also suitable for the analysis of carbohydrates.
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  • 24
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    Chromatographia 15 (1982), S. 161-166 
    ISSN: 1612-1112
    Keywords: Reaction detectors ; Liquid chromatography ; Pharmaceutical analysis ; Environmental analysis ; Trace organics analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reaction detectors are considerably enhancing the application potential of HPLC particularly when dealing with trace analysis in complex matrices. In principle one distinguishes between segmented and non-segmented reactor system. The theory of band broadening of these designs and some criteria for the choice of the proper type are brieffly discussed. It seems that with a proper construction of the phase separators segmented systems have a wider range of applicability. Applications of reaction detectors in the areas of pharmaceutical and environmental analysis are discussed.
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  • 25
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    Chromatographia 15 (1982), S. 277-281 
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Solvent selectivity ; Steroids ; Amine bonded phase ; Overlapping resolution mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Resolution (Rs) is a function of three factors: efficiency, retentivity and selectivity. A procedure for optimization of mobile phase selectivity was demonstrated using a reversed-phase (RP) separation of compounds with various functionalities. In this paper, the same procedure is used with normal bonded-phase (NP) chromatography to develop a separation of structurally similar steroids. The optimization of mobile-phase selectivity provided increased problem-solving capability and decreased the analysis time.
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  • 26
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Dilution and signal enhancement factor ; Maximum injection volume ; Calculation methods ; HPLC small volume columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The responding signals of eluted components can be enhanced by using high performance small volume columns with long lengths generating more plates than required for a separation with a preset resolution in combination with instruments which show very small external bandbroadening. The excess number of plates is then consequently erased by maximizing the injection volume of the sample until the preset resolution is reached. Equations, describing the dilution, relative signal enhancement and maximum injection volume as a function of the process parameters are derived and experimentally verified. Theory and experiment are in agreement only if variances of response functions are calculated as their second normalized central moments.
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