Comprehensive analysis of drugs of abuse in urine using disposable pipette extraction

The extraction of basic, acidic, and neutral drugs of abuse from a low volume of urine (0.2 mL) using disposable pipette extraction (DPX) is described. DPX is a solid-phase extraction device that uses loosely contained sorbent inside a pipette tip fitted with a screen. This device provides faster extraction times because conditioning steps are not required. In this study, the DPX used a modified divinyl benzene sorbent containing both cation-exchange and reversed-phase mechanisms that facilitates the retention of basic and acidic/neutral drugs, respectively. With this device, a comprehensive method of analysis was developed for a diverse group of drugs and drug classes in urine including amphetamines, opiates, cocaine and its metabolites, tetrahydrocannabinol metabolite, tricyclic antidepressants, meperidine, methadone, and phencyclidine. Recoveries of the majority of drugs analyzed were 90% or greater with relative standard deviations of less than 10%. Additional validation involved the analysis of urine specimens previously analyzed by a local forensic toxicology laboratory.