Colorimetric determination of hippuric acid in urine and liver homogenate.

To a dried extract Containing hippuric acid (HA), 1.0 mL of acetic anhydride and 2.0 mL of 0.5% p-dlmethyiamlnobenzaldehyde (DAB) solution In pyridine were added, and the solution was kept at 40 O C for 1 h after thorough mlxing. The absorbance was then determlned at 458 nm agalnst a blank containing acetic anhydride, DAB, and pyridine. This method was in good agreement with Beer’s law within 1 to 100 pg and the mean f SD absorbance for 20 pg HA was 0.939 k 0.013 ( n = 5). The apparent molar absorptivity of 2.5 X 104/mol/cm, and the relative standard deviation of 1.4% was calculated.