Quantitative analysis of multiple illicit drugs in preserved oral fluid by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

We present a validated method for the simultaneous analysis of basic drugs which comprises a sample clean-up step, using mixed-mode solid-phase extraction (SPE), followed by LC-MS/MS analysis. Deuterated analogues for all of the analytes of interest were used for quantitation. The applied HPLC gradient ensured the elution of all the drugs examined within 14 min and produced chromatographic peaks of acceptable symmetry. Selectivity of the method was achieved by a combination of retention time, and two precursor-product ion transitions for the non-deuterated analogues. Oral fluid was collected with the Intercept, a FDA approved sampling device that is used on a large scale in the US for workplace drug testing. However, this collection system contains some ingredients (stabilizers and preservatives) that can cause substantial interferences, e.g. ion suppression or enhancement during LC-MS/MS analysis, in the absence of suitable sample pre-treatment. The use of the SPE was demonstrated to be highly effective and led to significant decreases in the interferences. Extraction was found to be both reproducible and efficient with recoveries >76% for all of the analytes. Furthermore, the processed samples were demonstrated to be stable for 48 h, except for cocaine and benzoylecgonine, where a slight negative trend was observed, but did not compromise the quantitation. In all cases the method was linear over the range investigated (2-200 microg/L) with an excellent intra-assay and inter-assay precision (coefficients of variation <10% in most cases) for QC samples spiked at a concentration of 4, 12 and 100 microg/L. Limits of quantitation were estimated to be at 2 microg/L with limits of detection ranging from 0.2 to 0.5 microg/L, which meets the requirements of SAMHSA for oral fluid testing in the workplace. The method was subsequently applied to the analysis of Intercept samples collected at the roadside by the police, and to determine MDMA and MDA levels in oral fluid samples from a controlled study.

Solid-phase extraction and cleanup procedures for determination of acrylamide in fried potato products by liquid chromatography/mass spectrometry.

In response to recent discoveries of acrylamide in heated foods, a solid-phase extraction and cleanup protocol was developed for the determination of acrylamide in fried or baked potato samples by liquid chromatography/mass spectrometry (LC/MS). The analyte was extracted from the matrix by using 2M NaCl, and an aliquot of the initial extract was loaded onto a reversed-phase cartridge. After the analyte was eluted from the cartridge, the eluate was cleaned up on a mixed-mode cation-exchange cartridge. The eluate was then evaporated, and the residue was reconstituted in mobile phase before LC/MS analysis. Recoveries, based on the recovery of an added internal standard, ranged from 96 to 101% with relative standard deviations (RSDs) of 5-11%. The response was linear for a concentration range of 100-2000 ng/g with a coefficient of determination (R2) of 0.992 (n = 25). An interday study showed good accuracy and precision of the method over a 3-day period with a recovery of 98% and an RSD of 9.5% (n = 15). The analyses of 6 potato chip samples showed concentrations of incurred acrylamide ranging from 260 to 1500 ng/g.

Mixed-mode solid-phase extraction procedures for the determination of MDMA and metabolites in urine using LC-MS, LC-UV, or GC-NPD.

A solid-phase extraction (SPE) procedure was developed for the liquid chromatographic-mass spectrometric (LC-MS) analysis of 3,4-methylenedioxymethamphetamine (MDMA) and its metabolites 3,4-methylenedioxyamphetamine (MDA) and N,alpha-dimethyl-(3-methoxy-4-hydroxybenzene) (HMMA) ethanamine in urine. The procedure, with modifications, was also demonstrated using LC-UV and GC-nitrogen-phosphorus detection (NPD). A mixed-mode cation exchange SPE cartridge was effective for both reducing matrix impurities and for preconcentrating the analytes for the analysis. The concentration range investigated spanned from 0.10 to 20 microg/mL with recoveries ranging from 88% to 108% for all analytes using LC-MS. Both LC methods and the GC method allow for complete resolution of MDMA, MDA, and HMMA, as well as the internal standards (MDMA-d5 and 3,4-methylenedioxypropylamphetamine) in less than 10 min. Lower limits of quantitation (LLOQ) for the LC-MS method were 0.1 microg/mL for MDMA and MDA and 0.04 microg/mL for HMMA. Compared with LC-UV and GC-NPD, the LC-MS method requires the least amount of sample manipulation and provided the highest sample throughput. GC-NPD gave comparable selectivity, but the extra sample manipulation steps required contributed to lower recovery, lower precision, and increased time for the analysis. LC-MS analysis demonstrated better selectivity for the determination of HMMA in incurred samples compared with LC-UV analysis.