Fast screening for drugs of abuse by solid-phase extraction combined with flow-injection ionspray-tandem mass spectrometry.

Abstract

A fast analytical approach for the simultaneous quantitative screening for illicit drugs in serum and urine without tedious chromatographic separation steps was developed by combining solid-phase extraction (SPE) followed by flow-injection analysis (FIA) with ionspray-ionization and tandem mass spectrometry (MS-MS) detection using a PE Sciex API 300 triple-quadrupole MS. MS-MS analysis was performed by sequentially isolating the precursor ions of the analytes and their deuterated standards with subsequent fragmentation and monitoring of one fragment ion for each substance. A multiple-reaction monitoring experiment was set up for morphine (MO), codeine (COD), amphetamine (AMP), benzoylecgonine (BZE), and their deuterated analogues. For method evaluation, serum samples spiked with 2-1000 ng of each drug and deuterated standards were extracted by mixed-mode SPE, redissolved in CH3CN-NH4OAc-buffer, and directly injected by flow injection into the ionspray source. The specificity of this new method was demonstrated by testing compounds with similar chemical structure for interferences from the analytes of interest (e.g., dihydromorphone, morphine glucuronide, and 6-monoacetylmorphine with MO; dihydrocodeine and hydrocodone with COD; cocaine [COC] and ecgonine methylester with BZE; methamphetamine with AMP). The possibility of interferences of such compounds with the FIA-ionspray-MS-MS screening method is discussed. Spiked serum samples and serum and urine samples from drug addicts and victims of drug abuse were analyzed with FIA-MS-MS and, after derivatization, with gas chromatography-mass spectrometry (GC-MS). Comparable quantitative results were obtained with both methods; no interferences with metabolites or other compounds were found. The FIA-ionspray-MS-MS method is a fast, quantitative, sensitive, and highly specific alternative method to drug-screening by immunoassays, high-performance liquid chromatography, and GC-MS. It can be used for the simultaneous detection of different drugs and metabolites such as opiates, COC, AMP derivatives, and many other drugs.