Use of a sulfate: hydrogen sulfate buffer to preserve urine for steroid analysis

1. HCI, commonly used to preserve urine for steroid analysis, cannot safely be supplied to out of town patients. 2. An equimolar mixture of Na2SO4 and NaHSO4 is a safe alternative which may be used to protect specimens en route to the laboratory. 3. Addition of bisulfate buffer to urine (20 g/l) reduced the pH to 2.0-3.5 (31 specimens; 24 hr urine volumes, 560-3320 ml). 4. Little change in pH was observed when buffered urine (12 specimens) was kept at 30 degrees for 14 days (initial pH 2.62 +/- 0.38 (mean +/- standard deviation); PH after 14 days, 2.59 +/- 0.48). 5. Analysis of the creatinine, 17-oxosteroids, 17-oxogenicsteroids, estrogens, pregnanediol, androsterone + etiocholanolone and estriol in urine samples acidified to pH 2-3 with HCl, and in the same samples acidified with buffer, gave results which were indistinguishable from each other. 6. Almost no change in steroid and creatinine concentrations was observed in samples of buffered urine kept for 10 days at room temperature (20-26 degrees).