Development of a fast method for simultaneous determination of hippuric acid, mandelic acid, and creatinine in urine by capillary zone electrophoresis using polymer multilayer-coated capillary

This paper reports the development of a fast separation method employing capillary zone electrophoresis for the simultaneous determination of hippuric acid, mandelic acid, and creatinine in samples of urine using a coated capillary. The background electrolyte was composed of 10 mmol L-1 tris(hydroxymethyl)aminomethane and 30 mmol L-1 2-hydroxy-isobutyric acid at pH 3.6. The internal standard was 3,5-dihydroxybenzoic acid. Separations were performed in a fused silica capillary (32 cm total length, 8.5 cm effective length, and 50 mu m internal diameter) coated with crosslinked hydroxypropyltrimethyl ammonium chloride chitosan and kappa-carrageenan. Direct UV detection was performed at a wavelength of 200 nm. Samples and standards were injected hydrodynamically (-50 mbar, 3 s) using the short-end injection procedure. The electrophoretic system was operated under constant voltage of 30 kV with positive polarity on the injection side. The separation time for hippuric acid, mandelic acid, and creatinine was less than 70 s. The evaluation of some analytical parameters of the method for the three analytes showed good linearity (R (2) > 0.99), limit of detections of 0.21 to 0.63 mg L-1, inter-day precision better than 3.0% (peak area), and recovery in the range of 98 to 106%. The method developed was applied in the analysis of the three analytes in urine samples.