Simultaneous Ion-Pairing Liquid Chromatographic Determination of the Major Metabolites of Styrene and Carbamazepine, and of Unchanged Carbamazepine in Urine

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Abstract
A high-performance liquid chromatographic method for a simultaneous quantitative determination of carbamazepine (CBZ) and of the major metabolites of CBZ (trans-10,11-dihydroxy-10,11-dihydrocarbamazepine, TDC; carbamazepine-10,11-epoxide, CBZ-E) and those of styrene (S) (hippuric acid, HA; mandelic acid, MA; phenylglyoxylic acid, PA) in the rat urine is described. Separation is achieved on a Nova-Pak reverse-phase column by isocratic elution. Excellent resolution was obtained by adding to the acetonitrile-water mobile phase, tetrabutylammonium chloride (0.005 M) and methanol (1%). Detection is effected by UV absorption at 230 nm with a total analysis time of less than 18 min. An aliquot of diluted urine is injected directly onto the liquid chromatographic column. The limits of sensitivity of CBZ, CBZ-E, TDC, HA, MA, and PA are 3.3, 2.0, 1.8, 3.1, 1.2, and 3.1 μg/ml of diluted rat urine, respectively. Precision and accuracy of the method are found to be acceptable. The method can be used for studying the interaction between these two xenobiotics. Preliminary studies have shown its potential application to human investigations.