Improved method for the determination of cyclic guanosine monophosphate (cGMP) in human plasma by LC-MS/MS

Cyclic guanosine monophosphate (cGMP) is an important second messenger molecule involved in gating ion channels and activating protein kinases. Here, we describe a validated LC-MS/MS method for the quantification of cGMP in human plasma, utilizing a stable isotope labeled analogue of cGMP as I.S. Plasma samples were extracted and concentrated by weak anion exchange solid phase extraction and the extracts were chromatographically separated on a porous graphitic carbon column. The analytes were detected by positive electrospray ionization and tandem mass spectrometry.The calibration function was linear in the range 1-20nM and the intra- and inter-day precision showed relative standard deviations of better than 2 and 6%, respectively. The accuracy was always better than 4%. Plasma concentrations in healthy human subjects determined with this method were 3.92 +/- 1.17 nM (n = 20). The method was due to its isotope labeled I.S., matrix independent. (C) 2009 Elsevier B.V. All rights reserved.