acetate (pH 9.5); the eluates were combined. To 1.5 mL of combined post-C18 eluate we added 0.1 mL of 0.25 mol/L KCN, 0.1 mL of 0.2 mol/L CuSO4, and 0.25 mL of ferric nitrate reagent (prepared from 100 g of ferric nitrate made up to 1 L with 0.4 mol/L nitric acid), with vortex-miring between additions, and measured the absorbance at 460 nm after 5 mm. Tests were performed in duplicate and a blank correction for each sample was obtained by adding the above reagents in reverse order to a third aliquot of urine supernate. Analytical recoveries of 20, 50, and 100 mol/L aqueous thiosulfate standards passed through the C18 column were 95%, 98%, and 96%, respectively; recoveries of urine with added 50 and 100 moJ/L thiosulfate were 94% and 91%. Thus the use of the C18 column permits a much simpler clean-up than the Sorbo method (5, 6), which used three ion-exchange columns (5). The good recoveries suggest that previously described inhibitors of the color development are also removed. No clinically significant interference was observed for urine specimens with added concentrations (mol/L) of ascorbate 100, acetoacetate 5000, acetone 500, ethanol 10 000, sulfate 100000, cysteine 500, cystine 500, acetaldehyde 500, or oxalate 500. The mean (range) urinary excretion of thiosulfate (moV24 h) in eight healthy male and three healthy female subjects was 25 (5-72) and 19 (4-34), respectively, similar to results reported by Sorbo and Ohman (5). We also report for the first time a dramatic effect of beer loading (1.1 L) in nonfastung ambulatory healthy men
,f. 115
(n = 3) on urinary thiosulfate (Figure 1). The mean thiosulfate excreted in urine at 0-3 and 3-6 h after beer ingestion was significantly greater (P
