Bioanalytical method for simultaneous determination of benzodiazepines in vitreous humor using liquid chromatography-tandem mass spectrometry.

The use of vitreous humor (VH) in forensic casework has been growing in the last years due to numerous advantages. Several compounds can be evaluated in this matrix, including benzodiazepines whose determination is essential due to their great availability and potential of dependance and misuse. Postmortem toxicological analyses are required to determine the influence of benzodiazepines in deaths. However, most of the analytical methods which determine these drugs in VH are laborious and time consuming. This article describes a simple method based on protein precipitation for the determination of eight benzodiazepines in VH samples. Samples were prepared through a protein precipitation method and analyzed by liquid chromatography tandem mass spectrometry. Solvent choice and sample and solvent volumes for precipitation were optimized using chemometric approaches. The method was validated for selectivity, lower limit of quantification (LLOQ), linearity, carryover, precision, bias, matrix effect and dilution integrity. In order to verify the applicability, 62 vitreous humor samples were analyzed. LLOQs were 1 ng/mL and calibration curves were linear from 1 to 25 ng/mL (r2 > 0,99) for all analytes. Bias, precision and dilution integrity results were satisfactory according to proper guidelines. Ionization suppression was significant with values ranging from 8 to 37%. Two samples from real cases were positive for diazepam with the following concentrations: 6.80 ng/mL and 47.68 ng/mL, approximately 10 times lower than those found in peripheral blood. The procedure described here can be used as a straightforward and low cost method for the quantitation of multiple benzodiazepines in VH.