A rapid and sensitive spectrophotometric procedure for the micro determination of carbamazepine in blood

An ultraviolet spectrophotometric procedure for the micro determination of carbamazepine in blood is described which is based on the original 9-methyl-acridine method proposed by Beyer, K.H. and Klinge, K. (1969) (Arzneim-Forsch. 19, 1759--1760). Carbamazepine is extracted from blood with dichloromethane, which is then washed with alkali and acid. An aliquot of the extractant is evaporated to dryness and the residue heated briefly with hydrochloric acid at 150 degrees C. Following removal of non-specific interference with n-heptane, the absorbance of the acid catalysed rearrangement product (9-methylacridine) is determined at 258 nm. The resulting procedure is rapid, reliable, sensitive and specific. It requires 100-200 mul sample for a single estimation and has a detection threshold of less than 0.1 mg/100 ml. It is concluded that the method is suitable for routine clinical use.