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  • Column liquid chromatography  (15)
  • Springer  (15)
  • Nature Publishing Group
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  • Springer  (15)
  • Nature Publishing Group
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  • 1
    Electronic Resource
    Electronic Resource
    Linear solvation energy relationships. A comparison of molar volume and intrinsic molecular volume as measures of the cavity term in reversed phase liquid chromatography (1986)
    Springer
    Chromatographia 21 (1986), S. 473-477 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase capacity factors ; Cavity term ; Molar volumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase liquid chromatographic capacity factors are well correlated by an equation of the form: $$logk' = (logk')_0 + mV/100 + s\pi ^* + b\beta + a\alpha $$ wheremV/100 measures the cavity term and π*, β, and α are the solvatochromic parameters that measure solute dipolarity/polarizability, hydrogen bond acceptor basicity, and hydrogen bond donor acidity respectively. Liquid molar volume (molecular weight divided by liquid density at 20°C) $$\bar V$$ , and computer-calculated intrinsic (van der Waals) molecular volume, $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ , are compared as measures of the cavity term in a number of correlations. $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ leads to more precise correlations as well as to a “cleaner” dissection of the multiple solute/solvent interactions. The opposing exoergic effect of solvent donor/solute acceptor hydrogen bonding, and endoergic cavity term are the main factors influencing HPLC capacity factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02341273
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  • 2
    Electronic Resource
    Electronic Resource
    Olefin group selectivity in non-aqueous reversed-phase LC (1988)
    Springer
    Chromatographia 25 (1988), S. 327-331 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Olefin group selectivity ; Methylene group selectivity ; Non-aqueous reversed-phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of mobile phase composition upon olefin group selectivity (the ratio of the retention factor of a n-alkane to 1-olefin of equal carbon number) has been examined for non-aqueous reversed-phase liquid chromatorphy. Under time-normalized conditions, large variations in olefin group selectivities were noted as the mobile phase constitutents were changes. However, methylene group selectivities were found to be insensitive to the nature of the mobile phase under these conditions. Mobile phases containing alcohols demonstrated low olefin group selectivities compared to those containing acetonitrile as weak solvent. The results of this study explain variations previously observed in the LC separation of olive oil triglycerides that differ in the number of methylene groups and double bonds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324709
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  • 3
    Electronic Resource
    Electronic Resource
    On-line procedures for the phase-transfer-catalyzed dansylation of phenolic steroids — Application to biological samples (1988)
    Springer
    Chromatographia 26 (1988), S. 267-273 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phase-transfer catalysis ; On-line derivatization ; Phenolic steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Commercially available equipment from two manufacturers served to set up an automated system for the precolumn phase-transfer-catalyzed dansylation of phenolic steroids, using ethynyl estradiol (EE) and estradiol (E) as model compounds. Using different mixing techniques, the on-line determination of EE and E in 200μl untreated urine samples was achieved at a rate of 3–8 analyses per hour. Detection limits were calculated to be 3–5 ng/ml. Calibration curves in urine were linear over two orders of magnitude with r=0.999 (n=5) for EE and r=0.999 (n=6) for E. The repeatability of the determination of EE in urine (1μg/ml) was 3.9% (RSD; n=20) and of E (1.5μl/ml) 3.8% (RDS; n=10). The use of plasma instead of urine in the on-line procedures was not possible due to rapid formation of emulsions, but E and EE were determined in 100μl plasma samples using a mild off-line mixing procedure in 10min. Detection limits were calculated to be ca 10ng/ml. A reaction detector, based on a solvent-segmented system, was developed for the on-line post-column dansylation of phenols and was coupled with a reversed-phase LC system. The highly selective system showed excellent linearity over at least two orders of magnitude with r=0.9999 (n=6) for both phenol and 2,5-dimethylphenol. The reproducibility was good with RSD values of around 2%. Detection limits for loop injections from standard solutions were calculated to be between 4 and 11ng.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268165
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  • 4
    Electronic Resource
    Electronic Resource
    Immunoaffinity precolumn for selective sample pretreatment in column liquid chromatography: Immunoselective desorption (1991)
    Springer
    Chromatographia 31 (1991), S. 469-477 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Immunoaffinity precolomn ; Oestrogens ; Bioanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automated liquid chromatographic system is described using immunoaffinity precolumns for sample pretreatment. The system consists of a column-switching unit allowing preconcentration from a large volume of sample (e.g. 15 ml of urine) onto an immunoaffinity precolumn (containing polyclonal antibodies immobilized on Sepharose). After sorption, the analytes are desorbed by a mixture of two cross-reacting solutes, followed by reconcentration on a C-18-bonded silica precolumn, and then separation on a C-18-bonded silica analytical column. Using oestrogen steroids as model compounds and UV absorbance detection, the minimum detectable concentration is ca. 200 ng/l with a repeatability of 6–8%. The total analysis time is 45 min which allows the unattended analysis of 30 samples per day. The features of the sample pretreatment method, especially of the immunoselective desorption, are evaluated and the general applicability of the system is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262391
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  • 5
    Electronic Resource
    Electronic Resource
    On-line post-column extraction in column liquid chromatography with electron-capture detection (1986)
    Springer
    Chromatographia 22 (1986), S. 235-240 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase system ; On-line post-column extraction ; Electron-capture detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A post-column extraction module has been used for the on-line coupling of conventional-size (4.6mm i.d.) reversed-phase liquid chromatography (PPLC) and electron-capture detection (ECD). Hexane and toluene were used as extraction solvents, while methanol turned out to be preferable to dioxane and acetonitrile as modifier in the aqueous eluent. In this system the ECD behaves as a concentration-sensitive detector. The band broadening in the evaporation interface, which connects the extraction module with the ECD, dominates the total post-column band broadening; it can be reduced to 3–4 sec by directing at least 0.25–0.30 ml/min (i.e. 25–30%) of the extraction solvent to the ECD. Optimal signal-to-noise ratios were observed if 30–60% of the extraction solvent is directed to the ECD. The noise levels are 5–10 times higher than in systems using a direct coupling of normal-phase LC or narrow-bore reversed-phase liquid chromatography to the ECD. Separations of phenylurea herbicides and chlorophenols demonstrate the applicability of the RPLC-extraction module-ECD system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268765
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  • 6
    Electronic Resource
    Electronic Resource
    Pretreatment of body fluids by preparative isotachophoresis prior to chromatographic analysis (1988)
    Springer
    Chromatographia 26 (1988), S. 351-358 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isotachophoresis ; Sample pretreatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This study focusses attention on the possibilities of preparative isotachophoresis (ITP) as a sample pretreatment technique prior to liquid chromatographic (HPLC) analysis. The increased demand for accurate and less time consuming analysis necessitates that sample pretreatment procedures, should be develop in parallel with other improvements (e. g. in detection and separation) which can be observed. The preparation isotachophoresis was performed on gel slabs and the zones of interest were subsequently cut out, desorbed and the desorbates analyzed by HPLC. In this study satisfactory recoveries of between 85–90% with a standard deviation of 1–5% were observed for blank experiments. For spiked serum and urine samples the recoveries in general decreased with decreasing spiked drug concentrations. These observations are discussed in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268180
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  • 7
    Electronic Resource
    Electronic Resource
    The rapid quantitative analysis of codeine phosphate drug substance by reversed-phase high-performance liquid chromatography (1985)
    Springer
    Chromatographia 20 (1985), S. 289-292 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase ; Codeine phosphate drug substance ; Opium alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid procedure for the evaluation of codeine phosphate drug substance derived from poppy straw or opium concentrate is described. The gradient HPLC procedure employs a pH 2.5 phosphate buffer, methanol and acetonitrile mobile phase at 40°C and a μBondapak C-18 column. Eight opium alkaloids, including the four major alkaloids, are separated from each other. The paper describes details of the assay procedure and presents data documenting the linearity, specificity, precision, and sensitivity of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02310385
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  • 8
    Electronic Resource
    Electronic Resource
    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary New multidentate phenyl-bonded phases (MPBPs) were synthesized and evaluated the chromatographic retention behaviour with polycyclic aromatic hydrocarbons as sample probes in high-performance liquid chromatography. The new MPBPs show different retention characteristics from the previously synthesized MPBP, designated TP. Nevertheless, the results indicate that the retention mechanism is still the same as the TP phase: the size and shape of the solute molecule can be recognized by a cavity-like space formed by the methyl groups and phenyl rings of MPBPs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268372
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  • 9
    Electronic Resource
    Electronic Resource
    Study on retention behavior of peropyrene-type polycyclic aromatic hydroccrbons with various bonded stationary phases in reversed-phase liquid chromatography (1988)
    Springer
    Chromatographia 25 (1988), S. 483-486 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase diphenyl and naphtylethyl bonded phases ; Retention/molecular polarizability relationships ; Peropyrene aromatics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behavior of 15 peropyrene-type polycyclic aromatic hydrocarbons was investigated on various bonded stationary phases in reversed-phase liquid chromatography. On diphenyl and naphthylethyl bonded phases, high correlations were obtained between the molecular polarizability of solutes and their retention. However, very low or no correlations were found on various octadecyl bonded phases. These facts are discussed by using the electrostatic interaction concept between the solutes and the stationary phase. We conclude that these observations are due to two reasons: the difference in the degree of planarity of polycyclic aromatic hydrocarbons and the high ability of planarity recognition of octadecyl bonded phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324817
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  • 10
    Electronic Resource
    Electronic Resource
    The use of large polycyclic aromatic hydrocarbons to study retention in non-aqueous reversed-phase HPLC (1989)
    Springer
    Chromatographia 27 (1989), S. 118-122 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265862
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