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The determination of sulphate in plasma is described, making use of reversed-phase high-performance liquid chromatography with ultraviolet detection. The concentration of inorganic sulphate determined in plasma of twenty healthy volunteers was 0.307 +/- 0.092 mmol/l (mean +/- S.D.). In one stable chronic dialysis patient the kinetics of plasma sulphate removal were monitored during and after one single pass dialysis. In addition, plasma sulphate concentrations were determined in three stable chronic dialysis patients during a consecutive scheme of two single pass dialyses, five Redy dialyses and three single pass dialyses. As expected, plasma sulphate accumulates in plasma to a high steady-state level under Redy dialysis, whereas during single pass dialysis sulphate is efficiently removed.

The simultaneous determination of some hydroxycholesterols in human serum samples is described. The procedure is based on hydrolysis and extraction of these compounds in serum samples, followed by removal of especially cholesterol (making use of reversed-phase high-performance liquid chromatography) and derivatization of the purified compounds to their trimethylsilyl ethers and subsequent gas chromatography using flame ionization detection. Serum levels of 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol and 26-hydroxycholesterol were determined in several groups of patients: normals, untreated patients suffering from cerebrotendinous xanthomatosis, patients suffering from cerebrotendinous xanthomatosis and treated with either chenodeoxycholic acid or cholic acid in an effective dose, patients suffering from cerebro-hepato-renal syndrome, patients suffering from hypercholesterolemia and treated with cholestyramine for prolonged periods and one patient presumed to be suffering from an inborn error of metabolism in bile acid synthesis. It can be concluded that the 7 alpha-hydroxycholesterol concentration in serum is a good parameter for establishing disorders involving the metabolic conversion of 7 alpha-hydroxycholesterol towards bile acids. In addition, 26-hydroxycholesterol levels in patients suffering from cerebrotendinous xanthomatosis are beyond detectable limits, even during treatment with bile acids in an effective dose, whereas in all other conditions this compound is substantially present.

A newly devised procedure for a simultaneous determination of urinary tetrahydroaldosterone and aldosterone is described. The procedure is based on deconjugation and acetalization, followed by extraction and derivatization of the urinary compounds to their trimethylsilyl ethers and subsequent gas chromatographic-mass fragmentographic detection. To evaluate the assay, aliquots of a urine sample of a healthy individual were analysed in multiplicate; a mean tetrahydroaldosterone concentration of 103 nmol/l and a within-sample, within-day- and day-to-day coefficient of variation of 1.8, 3.2 and 3.4%, respectively, were found. Determination of aldosterone in the same sample yielded a mean concentration of 25.3 nmol/l and the following coefficients of variation: 2.8% (within-sample), 3.8% (within-day) and 4.3% (day-to-day). The urinary excretion of tetrahydroaldosterone and aldosterone in 24-h urine portions was determined in twenty healthy individuals, aged 23-77 years; for tetrahydroaldosterone and aldosterone, an excretion of 94 +/- 66 nmol per 24 h and of 40 +/- 22 nmol per 24 h was found, respectively, in accord with the literature. An example of the usefulness of the described assay is given by establishing the cause of severe salt-wasting in an infant; a highly elevated tetrahydroaldosterone and aldosterone excretion was demonstrated, proving that the child suffered from unresponsiveness to aldosterone (pseudohypoaldosteronism).