[Determination of hippuric acid and methylhippuric acid in urine by high performance liquid chromatography after extracted with acetonitrile].

To establish pretreatment conditions of hippuric acid (HA)and methyl-hippuric acid (MHA)in urine and HPLC conditions.HA and MHA in urine were extracted with acetonitrile under acid condition and determinated by HPLC-DAD. The operating conditions by HPLC were C18 column (150 mm× 4.6 mm, 5 μm), methanol-0.2% acetic acid (contained 6.5 mmol/L potassium dihydrogen phosphate)(25∶75, V/V) as mobile phase,1 ml/min as flow rate and wavelength was at 254 nm.The standard curves for HA, 2-MHA and 3-MHA(4-MHA)showed good linearity between 9.91~2 974.20 μg/ml(r=0.999 98), 1.91~573.60 μg/ml (r=0.999 84)and 2.00~598.65 μg/ml (r=0.999 85), respectively. The mean recoveries were 96.38%~98.01%, 83.17%~94.05 %, 103.22%~104.45%, respectively. The within-run precision were 0.50%~1.20%, 0.51%~1.59%, 0.49%~0.95%, respectively, and the between-run precision were 1.70%~3.20%, 1.30%~2.67%, 0.86%~2.74%, respectively. The detection limit of HA, 2-MHA and 3-MHA(4-MHA)were 0.18 μg/ml, 0.46 μg/ml and 0.12 μg/ml, and the low determination concentrations of the method were 0.36 μg/ml, 0.92 μg/ml and 0.24 μg/ml(1 ml urine). The urine can be kept 15 days at 4 ℃ refrigerator without significantly loss.This method with simply pretreatment conforms to the relevant requirements of guide for establishing occupational health standards-part 5: determination methods of chemicals in biological materials. It can be used to detect HA and MHA in urine for occupational population exposure to toluene and xylene.