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A new application of cyclodextrins is presented, being their use for sample purification. This new application is exemplified with a method for the determination of progesterone and testosterone in human serum based on isotope dilution gas chromatography/mass spectrometry. The whole procedure consists of a traditional solvent extraction with hexane for progesterone, respectively dichloromethane for testosterone, followed by a back-extraction of the steroids into a cyclodextrin-water solution. After washing of the aqueous phase with hexane, the steroids are finally extracted with toluene (progesterone) and dichloromethane (testosterone). Different cyclodextrins and cyclodextrin derivatives in various concentrations are investigated. A solution of 150 mmol/L hydroxypropyl beta-cyclodextrin in water is selected. The recovery of progesterone and testosterone is 70 and 80% respectively. The purification effectiveness, accuracy, and precision of the new method are equivalent to a traditional method using gel chromatography for sample purification.

Urinary 2-thioxothiazolidine-4-carboxylic acid is a useful indicator to assess the degree of occupational exposure to carbon disulfide. A new procedure is described for the isolation of this compound from urine prior to reversed-phase high-performance liquid chromatography. It is based on liquid-liquid extraction with methyl tert-butyl ether, followed by affinity chromatography on organomercurial agarose gel. 5-Carboxythiouracil is used as internal standard. The superior selectivity of affinity chromatography for the isolation of 2-thioxothiazolidine-4-carboxylic acid from urine permits an isocratic high-performance liquid chromatographic analysis. The total recovery of 2.5 mg of 2-thioxothiazolidine-4-carboxylic acid/g of creatinine in spiked urine by liquid-liquid extraction combined with affinity chromatography was 48.0% (SD 2.0%, n = 8). Within-run and within-day relative standard deviations averaged 4.0% (means = 2.48 mg/g of urinary creatinine, n = 9) and 6.5% (means = 1.19 mg/g of urinary creatinine, n = 15), respectively. The detection limit of the method was estimated at 0.05 mg of 2-thioxothiazolidine-4-carboxylic acid/g of urinary creatinine. The identity and spectral purity of 2-thioxothiazolidine-4-carboxylic acid detected in the urine extracts were confirmed by diode-array UV-vis detection. Typical 2-thioxothiazolidine-4-carboxylic acid levels in individual workers exposed to carbon disulfide ranged from nondetectable to 11 mg/g of urinary creatinine, several of which exceeded the generally accepted biological exposure index of 5 mg/g of urinary creatinine.