Performance characteristics of an LC–MS/MS method for the determination of plasma metanephrines

High mass accuracy assay for trimethylamine N-oxide using stable-isotope dilution with liquid chromatography coupled to orthogonal acceleration time of flight mass spectrometry with multiple reaction monitoring

“…Next steps for this transition will include the need for high mass accuracy instrumentation to overcome interferences that can affect the accuracy of measurement with 14 some nominal mass MRM systems [18,[26][27]. Initial exploration of this technology has already been done in toxicology laboratories [28].…”

Multiple Reaction Monitoring with Multistage Fragmentation (MRM3) Detection Enhances Selectivity for LC-MS/MS Analysis of Plasma Free Metanephrines

“…Previous studies have reported interferences in plasma metanephrine LC-MS/MS assays arising from prescription medications isoproterenol, isoetharine, and labetalol and from illicit substances and metabolites 3,4-methylenedioxy-N-methylamphetamine, 3,4-methylenedioxyamphetamine, and HMMA (5,6 ). Retrospective review of medications for the affected patient samples showed that, of the prescribed medications above, only 1 patient was on labetalol.…”

“…We prepared samples as described previously (5,26 ), with 100 L patient sample mixed with 100 L of 10 mmol/L ammonium phosphate buffer containing deuterated internal standards before being loaded onto an Oasis WCX Elution 96-well SPE plate. The metanephrines were later eluted with 3ϫ 30 L of 95:3:2 acetonitrile:water:formic acid.…”

“…We performed LC-MS/MS analyses for the routine MRM method as described previously (5,24,26,27 ) with the following alterations. Prepared samples, calibrators, and quality controls (15 L) were injected onto a Prominence HPLC system (Shimadzu) coupled to an API QTRAP 5500 mass spectrometer (ABSciex) operating in positive ion electrospray mode.…”

“…Studies using LC-MS/MS have reported false-positive values that were attributed to preanalytical problems; e.g., blood samples taken with patients in sitting rather than supine position (26 ). More recent reports describe a number of drug and drug metabolite interferences that can falsely increase, or prevent the measurement of, plasma normetanephrine and metanephrine values determined by LC-MS/MS (5,6 ). Petteys et al demonstrated that the use of quantifier/qualifier ion ratios could provide additional protection from reporting a falsely raised value in these instances (5 ).…”