Determination of cabergoline by electrospray ionization tandem mass spectrometry: Picogram detection via column focusing sample introduction

An electrospray ionization tandem mass spectrometric method was developed f or low-picogram detection of an ergot alkaloid, cabergoline, in coyote plas ma extracts. Cabergoline is under investigation as an abortifacient in cani d species. Central to the successful development of this method was the abi lity to introduce relatively large sample volumes into the mass spectromete r. This was achieved by focusing the analyte on a conventional highperforma nce liquid chromatography guard column prior to elution into the spectromet er. Volumes up to at least 900 muL could be injected onto the guard column using a 100% aqueous mobile phase. Cabergoline retained on the column was e luted as a discreet band into the mass spectrometer by the rapid addition o f methanol (30%) to the mobile phase. As compared to flow injection sample introduction, the ability to inject larger sample volumes led to a greatly lowered detection limit. Using this technique and a modification of a previ ously reported extraction procedure, cabergoline could be determined in coy ote plasma at concentrations as low as 9 pg of cabergoline/mL of plasma.