Urine drug testing for opioids, cocaine, and metabolites by direct injection liquid chromatography/tandem mass spectrometry

A sensitive and specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the simultaneous quantification of opioids, cocaine, and metabolites in urine was developed and validated. A 10-muL aliquot of urine was injected directly onto the LC/MS/MS system. The lack of sample preparation substantially reduced total analysis time. Separation was performed by reversed-phase chromatography with gradient elution for all analytes in 26 min. Atmospheric pressure chemical ionization (APCI) was a rugged and efficient ionization technique for basic drugs. Identification and quantification was based on selected reaction monitoring (SRM). Calibration, with deuterated internal standards, was performed by linear regression analysis (weighting factor 1/x). Limits of quantitation (LOQ) were established between 10-100ng/mL and linearity was obtained up to a maximum of 10 000 ng/mL with an average correlation coefficient (R-2) > 0.99. Analytical validation criteria for specificity, precision, accuracy, dilution integrity, matrix effect, and stability were fulfilled. The method proved to be simple and time efficient, and was applicable for illicit drug use monitoring and methadone treatment compliance in clinical research projects at the National Institute on Drug Abuse (NIDA). Published in 2003 by John Wiley Sons, Ltd.