We describe a combined gas-chromatographic mass-spectrometric method for determination of theophylline in whole blood. With use of a probability-based matching approach, the extensive gas-chromatographic interference did not affect mass-spectrometric quantitation of theophylline. Concentrations expected and found were linearly related from 1 to 60 mg/liter; the run-to-run coefficient of variati...

1. Pratt, J. J., Steroid immunoassay in clinical chemistry. Clin. Chem. 24, 1869 (1978). 2. Shackleton, C. H. L., and Whitney, J. 0., Use of Sep-pak cartridges for urinary steroid extraction: Evaluation of the method for use prior to gas chromatographic analysis. Clin. Chim. Acta (in press). 3. Thenot, J.-P., and Horning, E. C., MOTMS derivatives of human steroids for GC and GC-MS studies. Anal...

A method for the determination of total bile acids in human feces that is suitable for routine application is described and discussed. Bile acids are extracted from freezedried feces with acetic acid and toluene, in the presence of the i?ternal standard 23-nordeoxycholic acid. After saponification of the extract, bile acids and the internal standard are methylated and converted by mild chromic ...

A short gas-chromatographic method for analysing urinary concentrations of 2,5-hexanedione is based on acid hydrolysis of urine at pH below 0.1 and "purification" of the urine samples by microcolumns containing an octadecyl-silane phase. A 5% acetonitrile solution allows a fairly selective elution of 2,5-hexanedione from the microcolumns. Recovery of 2,5-hexanedione from urine is as great as 79...

We compared results by a simplified colorimetric copper-soap method for serum free fatty acids (Clin, Chem. 19: 419, 1973, modified) with those by a gas--liquid chromatographic method. The modified method requires only 100 microliters of sample, its standard curve is linear from 0.1 to 4.0 mmol/L (reference interval for adults: 0.2 to 0.8 mmol/L), and it is suitable for use with newborns. Compa...

The 125I-radioimmunoassay for methaqualone in human urine was evaluated by a comparison with newly modified gas-liquid chromatographic and thin-layer chromatographic methods. The statistically significant sensitivity value for the radioimmunoassay was at 2 microgram of methaqualone per liter of urine. The coefficient of variation was 2.88 +/- 0.39% interassay and 2.71 +/- 0.16% intraassay. Ther...

We describe a ratio gas-chromatographic method for determination of cortisol production rate by measuring the isotope dilution of urinary cortisol metabolites. The method was calibrated by analyzing [3H]tetrahydrocortisol and [3H]tetrahydrocortisone of known specific activities. Results are reasonably well reproducible, the coefficients of variation ranging from 8-15% of allotetrahydrocortisol/...

We described a sensitive and precise high-pressure liquid-chromatographic method in which 5-(p-methylphenyl)-5-phenylhydantoin is used as the internal standard in determining carbamazepine in whole blood or plasma. Carbamazepine is well separated from normal blood constituents in less than 8 min, and other commonly used anticonvulsants do not interfere with the analysis. The sensitivity of this...

After a brief recall of the chromatographic principles, t h e different applications of gas chromatographic measurements of thermodynamic equilibria were reviewed. Gas and liquid chromatographies are now well known and elegant methods for measuring the physicochemical properties and phase equil ibrium thermodynamic constants. Although fundamentally a dynamical method and mostly known as a power...