Quantitative determination of azure A in urine.

HE INTRODUCTION OF the carboxylic acid cation exchange Amberlite XE-96 (or IRC-50) Azure A resin’ as the medium for hydrogen ion exchange in place of the quininium exchange resin has simplified greatly the determination of gastric acidity without intubation (1). Solvent extraction and fluorimetry are no longer required. The amount of blue dye excreted in the urine is readily measured by visual comparison against standards. In connection with a large-scale screening program, and other studies on gastric secretion now under way in this laboratory, the comparison block procedure (2) for the approximate estimation of Azure A excretion proved cumbersome and did not lend itself readily to the processing of many specimens. The following modification is rapid, is simple to carry out, and has given more exact quantitative data required for our study.