This study evaluates the pretreatment for analysis of benzidine metabolites in urine by measuring the recovery rates according to the temperature and periods of storage of the urine. By the solid phase extraction, the recovery rates of basic hydrolysis are benzidine 67.4 %, monoacetylbenzidine 105.1 %, and diacetylbenzidine 115.8 %, respectively. By the liquid extraction, the recovery rates of back-extraction into 0.1 M perchloric acid are benidine 105.7% monoacetylbenzidine 94.2 %, diacetylbenzidine 72.8 %, respectively. The difference of the recovery rates between the back-extraction into 0.1 M HCl and 0.1 M perchloic acid after basic hydrolysis are 101 % and 98.8 %, respectively. When the recovery rates of the urinary samples of pH 3, pH 7, pH 12 at 25 ℃ and -76 ℃ are compared for four weeks, there are no differences according to the temperature and the periods of storage.
The above results show that the solid phase extraction and back-extraction by 0.1 M perchloric acid after basic hydrolysis are suitable for the analysis of benzidine metabolites. There are no difference of the recovery rates of the urinary samples stored at 25 ℃ and -76 ℃ at pH 3, pH 7, pH 12, respectively for 28 days.
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