Simultaneous determination of hippuric acid and methyl hippuric acid in urine by capillary electrophoresis

A method for simultaneous determination of hippuric acid and methyl hippuric acid in urine by capillary electrophoresis(CE) was established.The sample was extracted with ethyl acetate and the extract was dried up under nitrogen gas.The residue was redissolved in a running buffer solution and analyzed by CE.The experimental parameters were as follows: an uncoated fused-silica-capillary(50 cm×50μm,41 cm effective length) was used as the separation column;a mixed 20 mmol/L borax buffer(pH 9.3) and acetonitrile(80:20,V/V) was used as the running buffer;the detection wavelength was 230 nm;the electrophoresis temperature was 20℃;gravity sampling time was 10s with gravity sampling height of 20 cm and the running voltage was 20kV.Under the optimized conditions,the linear ranges of the method for hippuric acid and methyl hippuric acid were all in the range of 2～50 mg/L with the correlation coefficients of 0.9998 and 0.9994,respectively.The detection limits were 0.26 mg/L and 0.20 mg/L,respectively.The spiked recoveries were 100.7%～115.5% and 93.3%～116.7%,respectively.The method is simple,sensitive,accurate and suitable for the determination of hippuric acid and methyl hippuric acid in urine.