Abstract
A color reaction involving a keto acid or hydroxy acid, a metal ion such as Al (III). and a xanthene dye was studied. A method for the spectrophotometric determination of keto acids or hydroxy acids (e.g., β-phenylpyruvic acid, PPA) with 9-(2'-carboxyphenyl)-4, 5-dibromo-2, 3, 7-trihydroxy-6-fluorone (bromohydroxyhydroquinonephthalein. Br. Qn. Ph.) and Al (III) was established. A detection test for PPA on a spot plate was also examined. This method is based on the formation of the Br. Qn. Ph. -Al (III)-PPA complex, which has an absorption maximum at around 570nm. The present method could be used to determine up to 20 μg/10ml PPA, and the apparent molar absorptivity was calculated to be 8.4×104 dm3 cm-1 mol-1. This method is superior to the other spectrophotometric methods in sensitivity. Recovery of PPA added to human urine was good.
