Measurement of succinylcholine concentration in human plasma by electrospray tandem mass spectrometry

An electrospray mass spectrometric method for the quantification of the dep olarizing neuromuscular blocking agent succinylcholine (SUX) is described. An extraction method compatible with direct infusion inlet was developed an d leads to an analysis cycle time of 7-8 min instead of 25 min that would b e required for HPLC inlet. SUX was extracted from human plasma on C1 solid- phase cartridges and was analyzed using positive ion electrospray tandem ma ss spectrometry (ESI-MS/MS). SUX plasma concentrations were determined by a stable isotope dilution assay using hexadeuterosuccinylcholine diiodide (S UXd6) as the internal standard. The calibration curve was prepared using th e ratio of intensities of the major product ions in the collision-induced d issociation spectrum for known concentration ratios of SUX and SUXd6 in pla sma. Calibration curves for the quantification were linear from 25 to 4000 ng/ml. For intraday precision, CV were less than or equal to6% and accuracy ranged from 98 to 103%. For the interday precision, CV were less than or e qual to 10% and accuracy ranged from 90 to 102%. This method is specific, s ensitive, reproducible, and practical in a clinical setting. (C) 2001 Acade mic Press.