Analysis of benzodiazepines in dynamically coated capillaries by CE-DAD, CE-MS and CE-MS2.

The applicability of a low pH volatile electrolyte for fast analysis of benzodiazepines with CE-MS was investigated. The electrolyte is based on a commercially available CEofix buffer system that produces a substantial and highly reproducible electroosmotic flow through a dynamic double coating principle. The system was first evaluated with a mixture of benzodiazepine standards in CE-DAD and the electrolyte composition was further optimized for CE-MS. The LOD for the six selected benzodiazepines with CE-MS was ca. 100 ppb, except for diazepam, for which the LOD was lower than 50 ppb. RSDs varied from 0.51 to 1.02% (n = 7) for migration times and from 4.75 to 11.80% (n = 7) for peak areas. The method was successfully applied to the analysis of a spiked urine sample after solid-phase extraction (SPE). CE-MS2 was performed on a standard mixture.