Drug of abuse confirmation in human urine using stepwise solid-phase extraction and micellar electrokinetic capillary chromatography.

This paper demonstrates that most common drugs of abuse can be absorbed simultaneously onto a mixed-mode bonded-phase matrix and eluted sequentially in two to three steps for subsequent analysis by micellar electrokinetic capillary chromatography (MECC). Having on-column multiwavelength UV absorption detection, this is shown to be an attractive approach for confirmation testing of barbiturates, hypnotics, amphetamines, opioids, benzodiazepines, and metabolites of cocaine in a single aliquot of human urine. For these compounds, no hydroysis of the urine specimen or sample derivatization is required. Under the examined conditions using 5 mL of urine, excellent recoveries (80-90% level) and detection limits (about 100 ng/mL) are obtained. For patient urines which tested positively for different classes of drugs using immunological screening methods, a two-step extraction scheme is shown to provide extracts suitable for rapid MECC confirmation of the drugs of abuse.