Analysis for carbamazepine in serum by electron-capture gas chromatography

We describe an analytical method for determining carbamazepine in serum by electron-capture gas chromatography. A single-step extraction is followed by formation of the N-pentafluorobenzamide derivative with pentafluorobenzoyl chloride. For quantitation either of two internal standards may be used: 10-methoxy carbamazepine or 7-chloro-5,11-dihydrodibenz[b,e] [1,4]-oxazepine-5-carboxamide (Squibb Compound No. 10996). The procedure requires 0.5 ml of serum. Analytical recoveries are 96%. Coefficients of variation routinely are less than 2% for concentrations of carbamazepine that are within the therapeutic range.