Gas Chromatography Mass Spectrometry (GC-MS) for Identification of Designer Stimulants Including 2C Amines, NBOMe Compounds, and Cathinones in Urine.

Phenethylamine derivatives are being increasingly exploited for recreational use as "designer" stimulants designed to mimic psychostimulant properties of amphetamine or other illicit substances like 3,4-methylenedioxymethamphetamine (MDMA [ecstasy]). Clandestine operations meticulously design phenethylamines so the user can bypass legal action when detected, as many of these are yet to be regulated by government authorities. Substituted phenethylamines or 2C amines, N-methoxybenzyl derivatives of the corresponding 2C amines commonly known as NBOMe compounds, and cathinones are among the most commonly abused phenethylamines. Current FDA-approved assays used in screening for illicit drug use lack the sensitivity needed to detect designer stimulants making it challenging for toxicologists to accurately identify these compounds. Gas chromatography mass spectrometry (GC-MS) is a sensitive method for identifying designer stimulants. This unit describes and compares two qualitative GC-MS methods for identifying 2C amines, NBOMe compounds, and cathinones in urine. © 2017 by John Wiley & Sons, Inc.

Ultraperformance liquid chromatography-tandem mass spectrometry assay for iohexol in human serum.

BACKGROUND: Iohexol is an iodinated contrast dye that has been shown to be useful in the estimation of glomerular filtration rate (GFR) in patients with suspected renal insufficiency. We developed and validated an ultraperformance liquid chromatography (UPLC)-triple quadrupole mass spectrometry (MS/MS) assay for quantifying iohexol in human serum. METHODS: Sample preparation involved dilution of 50 microL serum with 400 microL water, followed by protein precipitation with zinc sulfate and methanol containing the structural analog ioversol as the internal standard. After 1:20 dilution of the supernatant with water, 5 microL was injected into the UPLC-MS/MS system. Chromatography was performed using a Waters Oasis HLB 5-microm particle size, 2.1 x 20 mm column maintained at 50 degrees C. We used a 1-step acetonitrile/0.1% formic acid gradient to elute the compounds of interest at a common retention time of 0.96 min. The multiple reaction monitoring transitions used for integration and quantification were m/z 821.7-->803.7 for iohexol and m/z 807.9-->589.0 for ioversol in the electrospray positive ionization mode. RESULTS: The assay was linear from 2.5 mg/L (lower limit of quantification) to 1500 mg/L iohexol, with a mean extraction efficiency of >99%. Recovery of nominal target concentrations was 99%-102%. Interassay imprecision ranged from 7.9% at a concentration of 2.5 mg/L to 4.1% at 1000 mg/L. Ion suppression studies showed no matrix effects on the ionization of the 2 compounds. CONCLUSIONS: This rapid UPLC-MS/MS method can be successfully used for quantifying iohexol in human serum.

Quantification of mycophenolic acid and glucuronide metabolite in human serum by HPLC-tandem mass spectrometry.

BACKGROUND: The potent immunosuppressant mycophenolic acid (MPA) is metabolized to an inactive glucuronide (MPAG). The extent of metabolism varies among individuals, and the MPAG formed can be hydrolyzed to MPA and can displace MPA from serum albumin, creating a potential need to monitor both MPA and MPAG. METHODS: After addition of the carboxybutoxy ether of MPA (MPAC) as internal standard, MPA and MPAG were isolated from serum by acidification followed by solid-phase extraction. Gradient chromatographic separation was performed on a Waters Atlantis reversed-phase liquid chromatography (HPLC) column, and the compounds were quantified by electrospray ionization tandem mass spectrometry (MS/MS) in the multiple-reaction monitoring mode. Results obtained by HPLC-MS/MS were compared with an HPLC assay using ultraviolet detection (HPLC-UV) performed at a reference laboratory. RESULTS: MPAG, MPA, and MPAC were fully separated during a 7.0-min run time. Precision at both low and high concentrations of MPA ad MPAG met the suggested method validation criteria from a consensus panel report on MPA. The extraction efficiencies were 99% for MPA and MPAG. The assay was linear to 16 mg/L for MPA and 200 mg/L for MPAG. Limits of quantification were 0.1 mg/L for MPA and 1 mg/L for MPAG. Regression analysis gave the following results: HPLC-MS/MS = 1.03(HPLC-UV) - 0.03 mg/L (R2 = 0.982) for MPA; and HPLC-MS/MS = 0.93(HPLC-UV) + 0.89 mg/L (R2 = 0.967) for MPAG. CONCLUSION: This HPLC-MS/MS assay can be used to reproducibly quantify MPA and MPAG across a large analytical range in serum from organ transplant patients.