Micromethod for Determination of Diazepam by Electron-Capture Gas-Liquid Chromatography

We used 100 l of plasma for the determination of di-azepam. After the internal standard, prazepam, is added, the serum is directly extracted with diethyl ether, the ex-tract is evaporated, the residue is dissolved in ethanol, and the drug is measured by gas-liquid chromatography, with use of an electron capture detector. With this procedure, 2.5 ng of diazepam in the sample can be speedily mea-sured with specificity, accuracy, and reproducibility (CV = 4.5%). AdditionalKeyphrases:pediatric chemistry. drug assay monitoring therapy Diazepam is widely used as an adjuvant to anticonvulsant therapy. Information on the concentrations in blood of anti-convulsant drugs are of clinical value in the management of epilepsy. We propose here a very rapid and simple micro-method for determining diazepam. Only gas-liquid chromatographic methods involving the use ofan electron capture detector are adapted to therapeutic ranges of this drug. Methods for determining benzodiazepine without hydrolysis have already been published. Some authors (1, 2) report time-consuming methods with multiple extrac-tions with ether. Howard et al. (3) use a simple extraction technique,but the diazepam curve is nonlinear, and the pro-cedure requires 1 or 2 ml of plasma, which is too much in the case of neonates. Others (4,5) determine this drug in a 100-pl sample after extraction with benzene. The toxicity of the solvent, the addition of the internal standard just before the injection,and the poor linearityare the main disadvantages. Scagliola (6) describes a technique for use with a 100-pl sample but with multiple extraction steps. The micromethod we propose involves direct determination of the compound in a 100-pl plasma sample, with only one extraction step. Sensitivity, specificity, and reproducibility are excellent, and the method is suitable for use in routine analysis