Modified carbon-paste electrodes as sensors for the determination of 1,4-benzodiazepines: Application to the determination of diazepam and oxazepam in biological fluids

The determination of benzodiazepines in biological fluids is object of great interest for many scientists. In the daily medical practice, it is necessary to perform drug analytical monitorization in order to adequate the dose of these substances to the necessities of the patients, and to avoid toxic effects. In forensic toxicology, benzodiazepines are often found in fatal cases of drug intoxication, as well as in the blood of drivers involved in traffic accidents. These reasons justify the necessity of developing new analytical methods for their determination. The main objective of this paper consists of the development of an electrochemical procedure to analyse benzodiazepines and/or their metabolites in a sensible, versatile and economic way, in biological fluids, such as plasma and urine. A whole electrochemical study of diazepam, temazepam and oxazepam using modified carbon-paste electrodes is reported. Using the optimal conditions for the voltammetric measurements of these pharmaceuticals, diazepam was determined in plasma and oxazepam in urine. Due to the complexity of these biological matrices, a previous solid-phase extraction (SPE) procedure was necessary to separate the active principles before their determination. The best results were obtained for the determination of oxazepam in urine.