Solid-phase extraction of 1,4-benzodiazepines from biological fluids.

The solid-phase extraction (SPE) of seven 1,4-benzodiazepines (oxazepam, diazepam, temazepam, nordazepam, brotizolam, adinazolam and midazolam) using prazepam as internal standard was investigated. The 1,4-benzodiazepines were recovered from an aqueous buffer of suitable pH, using C18 Sep-Pak cartridges and mixtures of methanol-water as elution solvent. The recovery of oxazepam using different sorbent materials (C2, C8, C18, cyanopropyl, phenyl and cyclohexyl Bond-Elut) was also examined as a function of pH and the composition of the elution solvent. The SPE of oxazepam was investigated using spiked urine samples and the C2 cartridge gave rise to the cleanest urine extracts. The recoveries of the other 1,4-benzodiazepines from spiked urine and plasma samples using the C2 cartridge was then found to be higher than 90%, without any interference from endogenous compounds of the samples. Finally, the influence of other factors such as drug concentration, sample volume and the number of times the SPE cartridge had been used was also examined.