Trace analysis by peak compression sampling of a large sample volume on microbore columns in liquid chromatography

Šlais, Karel; Kouřilová, D.; Krejčí, M.

doi:10.1016/s0021-9673(00)91614-5

Cited by 45 publications

(11 citation statements)

References 16 publications

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“…Mills et al [25] also derived a factor for preconcentration resulting from the step gradient using a vaguely described function of k 1 and k 2 in Slais et al [26]. Rather than finding the factor k 2 /k 1 they found the factor

{(1 \frac{1 + k_{2}}{1 + k_{1}})}^{2}

.…”

Section: Introductionmentioning

confidence: 99%

Quantitative evaluation of models for solvent-based, on-column focusing in liquid chromatography

Groskreutz

Weber

2015

Journal of Chromatography A

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On-column focusing or preconcentration is a well-known approach to increase concentration sensitivity by generating transient conditions during the injection that result in high solute retention. Preconcentration results from two phenomena: 1) solutes are retained as they enter the column. Their velocities are k′-dependent and lower than the mobile phase velocity and 2) zones are compressed due to the step-gradient resulting from the higher elution strength mobile phase passing through the solute zones. Several workers have derived the result that the ratio of the eluted zone width (in time) to the injected time width is the ratio k2/k1 where k1 is the retention factor of a solute in the sample solvent and k2 is the retention factor in the mobile phase (isocratic). Mills et al. proposed a different factor. To date, neither of the models has been adequately tested. The goal of this work was to evaluate quantitatively these two models. We used n-alkyl esters of p-hydroxybenzoic acid (parabens) as solutes. By making large injections to create obvious volume overload, we could measure accurately the ratio of widths (eluted/injected) over a range of values of k1 and k2. The Mills et al. model does not fit the data. The data are in general agreement with the factor k2/k1, but focusing is about 10% better than the prediction. We attribute the extra focusing to the fact that the second, compression, phenomenon provides a narrower zone than that expected for the passage of a step gradient through the zone.

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{(1 \frac{1 + k_{2}}{1 + k_{1}})}^{2}

.…”

Section: Introductionmentioning

confidence: 99%

Quantitative evaluation of models for solvent-based, on-column focusing in liquid chromatography

Groskreutz

Weber

2015

Journal of Chromatography A

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“…This effect is taken to profit for analyzing components present in trace amounts in the sample. Indeed, very large sample volumes can then be introduced in the column, which leaves a sufficiently large amount of these trace analytes in the column for leading to high enough detection signal-to-noise ratios at the column outlet and precise enough quantitative analysis [27][28][29][30][31][32][33][34][35][36][37]. If, instead, the sample solvent is stronger than the mobile phase, the analyte migration velocity in the sample solvent is larger than in the mobile phase.…”

Section: Introductionmentioning

confidence: 99%

Influence of a strong sample solvent on analyte dispersion in chromatographic columns

Mishra

Rana

Wit

et al. 2013

Journal of Chromatography A

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a b s t r a c tIn chromatographic columns, when the eluting strength of the sample solvent is larger than that of the carrier liquid, a deformation of the analyte zone occurs because its frontal part moves at a relatively high velocity due to a low retention factor in the sample solvent while the rear part of the analyte zone is more retained in the carrier liquid and hence moves at a lower velocity. The influence of this solvent strength effect on the separation of analytes is studied here theoretically using a mass balance model describing the spatio-temporal evolution of the eluent, the sample solvent and the analyte. The viscosity of the sample solvent and carrier fluid is supposed to be the same (i.e. no viscous fingering effects are taken into account). A linear isotherm adsorption with a retention factor depending upon the local concentration of the liquid phase is considered. The governing equations are numerically solved by using a Fourier spectral method and parametric studies are performed to analyze the effect of various governing parameters on the dispersion and skewness of the analyte zone. The distortion of this zone is found to depend strongly on the difference in eluting strength between the mobile phase and the sample solvent as well as on the sample volume.

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“…Slais et al (29) evaluated this combination for the determination of polynuclear hydrocarbons and chlorinated phenols in water. By using reversed-phase HPLC and amperometric detection, Slais et al (29) reported lower limits of detection from 20 to 280 ng/L of water (parts per trillion) when 1-mL sample enrichments were carried out directly on the analytical microbore column.…”

Section: Organic Pollutants In Watermentioning

confidence: 99%

High-Performance Liquid Chromatography for Determination of Trace Organic Compounds in Aqueous Environmental Samples

Graham

1986

Advances in Chemistry

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A review of high-performance liquid chromatographic (HPLC) instrumentation, techniques, and methodologies for the deter mination of trace organic compounds in water is presented. The review includes approaches to sample cleanup or analyte isola tion for those compounds likely to be candidates for analysis by HPLC. Column technology, as it contributes to the use of HPLC for trace organic analyses, is discussed. Finally, various tech niques for quantitative and qualitative detection of analytes are discussed. "W • Τ HAT IS IN THIS WATER?"This seemingly simple, yet horrendously complex question is being posed by increasing numbers of well-in formed and not so well-informed individuals. In the recent U.S. Envi ronmental Protection Agency (USEPA) report, "National Water Quality Inventory Report to Congress", two issues of national concern were identified: (1) pollution resulting from toxic substances and (2) con tamination and depletion of ground water. More than half the states reported ground water problems stemming from waste disposal, landfill seepage, and excessive depletion of ground water supplies. A diverse collection of highly skilled scientists and engineers will be needed to effectively address these ubiquitous problems and to provide meaning ful answers to the question "What is in this water?"As more people ask this question, a greater burden will fall on the

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Trace analysis by peak compression sampling of a large sample volume on microbore columns in liquid chromatography

Cited by 45 publications

References 16 publications

Quantitative evaluation of models for solvent-based, on-column focusing in liquid chromatography

Quantitative evaluation of models for solvent-based, on-column focusing in liquid chromatography

Influence of a strong sample solvent on analyte dispersion in chromatographic columns

High-Performance Liquid Chromatography for Determination of Trace Organic Compounds in Aqueous Environmental Samples

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