Sample preparation in the micro-determination of organic compounds in plasma or urine

High-performance liquid chromatographic analysis of hippuric acid in human blood plasma

A method has been developed for the isocratic high-performance liquid chromatographic analysis of hippuric acid in human blood plasma. After the addition of an internal standard (3-methoxysalicylic acid), plasma samples (1 ml) were made alkaline and extracted stepwise with methylene chloride and ethyl acetate. The detection limit was 50 pmol of hippuric acid per ml of plasma. The concentrations of hippuric acid in plasma from house painters (n = 8), with long-term exposure to solvent vapours from alkyd paints, were in the range 1-21 nmol/mol (median 11 nmol/ml). These values were statistically significantly higher than those for controls (n = 9): 2-8 nmol/ml (median 3 nmol/ml).

The disposition and metabolism of the synthetic prostaglandin fluprostenol (ICI 81,008) in the horse

1. Following single intramuscular doses of [14C]fluprostenol (0.5--2.4 micrograms/kg) to three female horses and to three gelded male horses, radioactivity was present in the plasma within 5 min; peak concn. (0.32--1.30 ng/ml fluprostenol equiv.) occurred 5 to 90 min after injection. Radioactivity was still present in the plasma of the females after three days. About 88% of fluprostenol is bound to plasma proteins. 2. Radioactivity was present in the parotid saliva of the gelded male horses within 10 min. Peak concn. (45--91 pg/ml fluprostenol equiv.) occurred from 5 min to 1 h after injection. Saliva : plasma concn. ratios varied inversely with saliva flow rate and limiting ratios were 0.33 and 0.41 for the combined results of two experiments on each of two male horses; the calculated value is 0.46 Chromatography indicated that the majority of plasma and saliva radioactivity was [14C]fluprostenol. 3. Excretion of radioactivity in the urine was rapid and virtually complete 12 h after dosing. The total radioactivity excreted in urine by the female horses was 45% of the dose (96 h) and by the gelded male horses 53% (30 h). About 30% of the radioactivity present in the urines was unchanged fluprostenol. 4. Faecal excretion, which was substantially complete after 2 days, accounted for 32% of the radioactivity administered to the female horses. 5. Tissue conc. of radioactivity in the female horses at four days were below the limits of detection (90 pg/g), but 0.2--0.9% of the dose was detected at the site of injection.

Rapid and simple clean-up and derivatization procedure for the gas chromatographic determination of acidic drugs in plasma

A rapid and simple clean-up and derivatization procedure that can be generally applied to the gas chromatographic (GC) determination of acidic drugs of various chemical and therapeutic classes is described. The drugs are extracted from acidified plasma with chloroform containing 5% of isopropanol, which is then evaporated. The residue is dissolved in toluene, then the drugs are back-extracted into a small volume of a methanolic tetramethylammonium hydroxide solution. The solution obtained is added to N,N-dimethylacetamide and the drugs are treated with n-butyl iodide and chromatographed as their n-butyl esters. Retention times are given for three different columns; the results show that in all but three instances one derivative is formed. The recoveries in the extraction steps were determined by GC and UV spectrophotometry. The recovery of the back-extraction and of the extraction from plasma with chloroform-isopropanol is fairly good. For some drugs toluene can be used as the extraction solvent, which has the advantage that no evaporation of the extract is necessary, and it can be extracted directly with the tetramethylammonium hydroxide solution. Chromatograms of blank plasma treated according to the described procedure do not show interfering peaks from endogenous compounds. The advantages of the proposed method are as follows. It is a standard procedure that can be used for different types of drugs, using one standard column, with no interference from endogenous compounds. Separation is achieved between drugs that differ only in the number or position of the methyl groups and between a drug and its demethylated metabolite(s). No decomposition of the products occurs during the alkylation process and injection of the resulting neutral solution is not detrimental to the column material.

Isolation of drugs from autopsy material by XAD-2 adsorption-elution technique. A routine procedure

The method of adsorption of drugs on Amberlite XAD-2 resin, followed by differential elution was under study during 1 1/2 year of routine use. The method allows a separation of acidic and basic drugs and--due to acid hydrolysis step before adsorption--assures better recovery of conjugated and protein-bound drugs. The amounts of various drugs, found in autopsy cases by the XAD-2 method were usually higher than those found by solvent extraction. The method applied requires 20 g of sample (biofluid or tissue) for general toxicological analysis.