Isothermal gas chromatographic method for the rapid determination of carbamazepine ("tegretol") as its TMS derivative.

A rapid, simple isothermal gas chromatographic (GC) method for the quantitation of carbamazepine ("Tegretol") in serum as its trimethylsilyl derivative has been developed. A single chloroform extraction using 1.0 ml of serum, a 10-min derivatization step, and analysis on a 3% OV-1 (methyl silicone) GC column gives a linear response to a carbamazepine concentration up to 25 mg/liter. A non-drug internal standard (tetracosane) compensates for variables in extraction, injection, and instrumental changes occurring during analysis. This method was found to be free of interferences from endogenous substances in the serum, as well as from toxic concentrations of commonly used drugs. Day-to-day precision at concentration levels of 2, 5, and 10 mg/liter ranged from 2.9 to 4.4% (CV). Standard addition studies of carbamazepine added to serum resulted in a mean recovery of 95%. To ensure accurate results, all standards were prepared in serum.