Quality control in the determination of cortisol in plasma/serum by using, on every sample, two different three-step separation methods including ultrafiltration, restricted-access high-performance liquid chromatography and reversed-phase high-performance liquid chromatography, and contrasting results to immunoassays

Mueller, H. W.; Eitel, Jürgen

doi:10.1016/0378-4347(95)00479-3

Cited by 12 publications

(8 citation statements)

References 16 publications

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“…A comparison of the values obtained by the three methods shows that the cortisol measurement by radioimmunoassay is significantly influenced by a hitherto unknown substance that has an Rf value similar to that of cortisol. This observation agrees with earlier investigations which demonstrated that human urine contains compounds which interfere with the radioimmunological cortisol measurement [9,10]. With respect to the cortisol values in the urine of cortisol-or ACTHtreated guinea pigs, the data obtained by HPTLC or HPLC agree with earlier investigations [1,2] and correspond to the changes of cortisol in the plasma [7,8].…”

Section: Discussionsupporting

confidence: 91%

“…of compounds detected may be even higher if washing of wood shavings is used for urine collection/cortisol analysis. Since previous reports indicated that HPLC is most suited for cortisol analysis in urinary extracts [9,10], I applied a similar method to the guinea pig urine. The results presented in this work show that the HPLC method was specific and precise.…”

Section: Discussionmentioning

confidence: 99%

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Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay

Fenske

1997

Chromatographia

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay

Fenske

1997

Chromatographia

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“…Standard curves were constructed by plotting the peak heights against the concentrations of the standards. Peak height values were used instead of peak area values, as it has been demonstrated that this gives improved precision and accuracy for low concentrations of voriconazole (12). In practice, a linear rela- tionship was found over a range of drug concentrations from 0.2 to 10 g/ml.…”

Section: Resultsmentioning

confidence: 99%

Comparison of High-Performance Liquid Chromatographic and Microbiological Methods for Determination of Voriconazole Levels in Plasma

Perea

Pennick

Modak

et al. 2000

Antimicrob Agents Chemother

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A new selective high-performance liquid chromatography (HPLC) method with UV detection for the determination of the investigational triazole voriconazole in human plasma by using acetonitrile precipitation followed by reverse-phase HPLC on a C 18 column was compared with a simple agar well diffusion bioassay method with Candida kefyr ATCC 46764 as the assay organism. Pooled plasma was used to prepare standard and control samples for both methods. The results of analyses with spiked serum samples (run as unknowns) were concordant by the bioassay and HPLC methods, with expected values being obtained. HPLC demonstrated an improved precision (3.47 versus 12.12%) and accuracy (0.81 versus 1.28%) compared to those of the bioassay method. The range of linearity obtained by both methods (from 0.2 to 10 g/ml for HPLC and from 0.25 to 20 g/ml for the bioassay) includes the range of concentrations of voriconazole (from 1.2 to 4.7 g/ml) which are considered clinically relevant. Although either methodology could be used for the monitoring of patient therapy, the smaller variability observed with HPLC compared to that observed with the bioassay favors the use of HPLC for pharmacokinetic studies.

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“…The precolumn concentration method is a useful pretreatment in the analysis of real samples by microcolumn LC, particularly in the analysis of biological samples, 6,7 as well as for environmental hormones analysis. 8,9 Similarly, on-column enrichment is also performed in order to increase the sensitivity of detection.…”

Section: Introductionmentioning

confidence: 99%

Determination of Inorganic Anions in Natural Water by Microcolumn Ion Chromatography with On-column Enrichment

2003

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Ion chromatography (IC) has been widely used in the determination of ionic species in drinking water, surface water, wastewater, etc. In most cases, the sample pretreatment involves only simple operations, such as filtration, protein precipitation, pH adjustment, dilution, and the extraction of the analytes. In some cases, the sample pretreatment can be difficult when the concentration of target ions in the sample is very low, or when the concentrations of the ionic matrix are too high relative to the analytes.Sample pre-concentration has been widely employed in HPLC in order to achieve a high concentration sensitivity separation of analytes.Liu et al. 1 proposed a simple sample preconcentration for the determination of trace levels of bromate and perchlorate in drinking water. The drinking-water sample was first treated with an Ag cartridge, and then concentrated 20-fold using a domestic microwave oven. A method for on-line pre-concentration and determination of Cr(VI) traces was developed by Padarauskas et al.2 by using a C18 column (50 × 6 mm i.d.). The technique has been successfully applied to the determination of Cr(VI) traces in drinking water as well as surface and ground-water samples.Efforts have also been made to inject large sample volumes 3,4 in order to enhance the detection sensitivity. In these trials, the advantage of combining microcolumn LC and particle beam MS is that this allows the determination of acidic pesticides at very low concentrations. The sample volume that could be injected into a packed capillary column was increased by 800 times. 4 Takeuchi and Ishii developed a precolumn concentration method in ultra-micro HPLC, and examined its application to trace analysis. 5 It was proven that the precolumns, which were about 1/10 to 3/10 of the length of the separation column, had shown a good enrichment efficiency in the separation of phthalates in water and corticosteroids in serum.The precolumn concentration method is a useful pretreatment in the analysis of real samples by microcolumn LC, particularly in the analysis of biological samples, 6,7 as well as for environmental hormones analysis. 8,9 Similarly, on-column enrichment is also performed in order to increase the sensitivity of detection. However, the on-column method is normally employed when using either gradient elution or a trap column, or when diluting the sample with a weak solvent. In these cases, it is common to inject large sample volumes in order to enhance the detection sensitivity. 10 On the other hand, in the case of a simple isocratic mode, large injection volumes would produce a wide initial sample zone, and thus create a large precolumn dispersion that severely degrades the resolution.Inorganic anions have a very close relation to environmental water.Lopez-Ruiz reviewed the advancement in the determination of inorganic anions by IC from 1997 to 1999. 11 These topics include new sample pretreatments, new separation methods, new detection systems, and the latest applications in the fields of environment, water, food, ...

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Cited by 12 publications

References 16 publications

Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay

Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay

Comparison of High-Performance Liquid Chromatographic and Microbiological Methods for Determination of Voriconazole Levels in Plasma

Determination of Inorganic Anions in Natural Water by Microcolumn Ion Chromatography with On-column Enrichment

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