Determination of Benzodiazepines in Urine by CE-MS/MS

Using capillary electrophoresis combined with tandem mass spectrometry, we have developed a method to simultaneously detect lorazepam, clonazepam, temazepam, oxazepam, diazepam, and nitrazepam in urine. The urine samples were submitted to a modified QuEChERS extraction procedure, followed by electrophoretic separation in 0.1 M formic acid electrolyte (pH 2.4) using a polyvinyl alcohol (PVA)-coated capillary. The correlation coefficients of the calibration curves, using matrix-matched benzodiazepines standard solutions at six different concentrations from 10 to 500 ng/mL, were up to 0.998. The limits of detection ranged from 0.9 to 1.4 ng/mL. We verified precision and accuracy through recovery for spiked urine blank samples at five concentration levels (10, 20, 50, 100, and 200 ng/mL) in triplicate. The recovery values ranged from 89 to 121 %, with a relative standard deviation lower than 6.0 %.