Comparative study of extraction methods for the GC and GC-MS screening of urine for beta-blocker abuse

Comparison is made between conventional liquid-liquid extraction and solid-phase extraction techniques using Extrelut-1, Extrelut-3 and C18-RP cartridges respectively for the screening of several beta-blockers in urine. Generally, using GC with nitrogen specific detection as the screening technique, liquid-liquid extraction and Extrelut-1 solid-phase extraction seem to be the methods of choice. However, when the screening and confirmation are performed by GC-MS, solid phase extractions with C18 or Extrelut-1 are valuable alternatives to conventional extraction. Using the different extraction techniques, detection limits and time periods during which the drugs are detectable in urine after oral administration of subtherapeutic amounts of several beta-blockers are determined.