Dynamic coating for fast and reproducible determination of basic drugs by capillary electrophoresis with diode-array detection and mass spectrometry

The double coating principle of CEofix® buffers was evaluated for the analysis of some basic drugs by capillary electrophoresis–diode-array detection (CE–DAD) and capillary electrophoresis–mass spectrometry (CE–MS). The involatile phosphate present in original low pH CEofix®, was replaced with formic acid for hyphenation of CE with MS. The double coating produces a substantial and highly reproducible electroosmotic flow (EOF), even at low pH. The rinsing procedure and electrolyte composition were optimized for both CE–DAD and CE–MS. The system was evaluated with the analysis of a mixture of basic drugs and a spiked urine sample enriched by solid-phase extraction (SPE). The R.S.D. values on the migration time and peak area measured for 28 analyses with CE–DAD were below 0.25 and 2.40%, respectively. For CE–MS, the R.S.D. on the migration time was 0.85% or less and the area precision ranged from 5.65 to 14.33% (for seven injections). The LOD with the developed CE–MS method was below 50 ppb for all five drug standards tested.