Determination of organophosphorus pesticides in wheat flour by supercritical fluid extraction and gas chromatography with nitrogen-phosphorus detection.

Application of supercritical fluid extraction (SFE) for selective isolation of organophosphorus pesticides from a real-world matrix (wheat flour) has been described. The method uses extraction with supercritical carbon dioxide at 206.8 bar and 60 degrees C, followed by quantitation by gas chromatography with nitrogen-phosphorous detection without clean-up of the extracts. Comparison of SFE with a method currently employed for sample preparation (i.e., organic solvent extraction followed by liquid-liquid extraction and gel permeation chromatography clean-up) shows that the SFE technique simplifies the sample preparation step and speeds up the determination of organophosphorus pesticides in flour. Extraction times were 60 min for a 7 g sample size. This technique was able to determine organophosphorus pesticides (ethoprophos, diazinon, chlorpyrifos methyl, fenitrothion, parathion, phenthoate, EPN) in samples at the 10 ng/g level.

Analysis of cholesterol and cholesteryl esters in human serum using capillary supercritical fluid chromatography.

Capillary supercritical fluid chromatography (SFC) using carbon dioxide as a mobile phase was applied for the determination of free cholesterol and cholesteryl esters in human serum. Serum samples were extracted with methanol-chloroform (2:1, v/v), and the extracts were analyzed by pressure programmed capillary SFC-flame-ionization detection (FID) without thermal degradation and derivatization. The total cholesterol concentrations obtained from SFC analysis were compared with those from GC or enzymatic analysis. The capillary SFC-FID method having high resolution gave an acceptable average relative standard deviation of 2.6%, and a detection limit of 4-6 pg. The quantitative results were acceptable for the simultaneous analysis of cholesterol and its esters in biological fluids. The concentration profiles of each compound in various samples, normal Korean human serum, Western human serum, and from high-cholesterol patient plasma, have been compared with this method.

Quantitative analysis of serum proteins separated by capillary electrophoresis.

The possibility of open tubular capillary electrophoresis for clinical diagnostic use is examined. Capillary electrophoresis was performed in an untreated 50 microns (i.d.) x 100 cm (65 cm to detector) capillary with detection of absorbance at 200 nm. Conditions for the separation of serum proteins without adsorption to the capillary surface were established. Quantitative analyses of serum samples from 38 patients with liver cirrhosis, nephrotic syndrome, or polyclonal gammopathy by capillary electrophoresis were done and the results were compared with those by conventional agarose gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All samples were analyzed in duplicate. We evaluated linearity of response, within-run CV, and the correlation between capillary electrophoresis and agarose gel electrophoresis.

Analysis of antiepileptic drugs in human plasma using micellar electrokinetic capillary chromatography.

We describe a method for the simultaneous determination of antiepileptic drugs (ethosuccimide, phenytoin, primidone, phenobarbital, carbamazepine and valproic acid) by micellar electrokinetic capillary chromatography using sodium dodecyl sulphate as the micellar phase. Factors affecting the micellar electrokinetic separation were studied for the quantitative determination of these drugs in human plasma. The confirmation of the peaks and the specificity of the method were investigated by combining multiwavelength detection with micellar electrokinetic capillary chromatography.

Separation of theophylline and its analogues by micellar electrokinetic chromatography: application to the determination of theophylline in human plasma.

Micellar electrokinetic chromatographic separation of theophylline and its analogues was investigated using sodium dodecyl sulphate (SDS) as a micellar phase. The effects of pH, micelle concentration, applied voltage and temperature on the separation and preliminary quantitative analysis were studied for the determination of theophylline in human plasma. The data indicate that this technique could be used as the reference or routine method of theophylline measurement in therapeutic drug monitoring.

Free solution capillary electrophoresis of proteins using untreated fused-silica capillaries.

Numerous efforts have been made to separate proteins by capillary zone electrophoresis (CZE). The most common optimization techniques are changing the pH of the running buffer, coating the capillary surface with a hydrophilic polymer, or using additives in the sample solution. Surface coatings and solution additives can reduce the adsorption of the protein onto the capillary surface, but they diminish the separation efficiency and the resolution of CZE. This paper reports the successful separation of proteins in a untreated fused-silica capillary by raising the pH of the running buffer and washing between runs with 1.0 M sodium hydroxide. Under these conditions, model proteins and proteins in human serum have been determined by CZE. It is shown that the results from CZE are compatible with those of sodium dodecyl sulphate-polyacrylamide gel electrophoresis.