Measurement of sub-picogram quantities of platelet activating factor (AGEPC) by gas chromatography/negative ion chemical ionization mass spectrometry.

A very sensitive method of 1-O-alkyl-2-acetyl-sn-glycerophosphocholine (platelet activating factor) quantitation is described. 1-O-Alkyl-2-acetyl-sn-glycerophosphocholine is converted to 1-O-alkyl-2-acetylglycerol by treating with phospholipase-C which is in turn acylated with pentaflurobenzoyl chloride. The resulting diglyceryl ester of pentafluorobenzene is analysed by gas chromatography/negative ion chemical ionization mass spectrometry. With methane as the reagent gas the pentafluorobenzoyl acyl derivative yields mainly the molecular anion ([M]-.) representing more than 92% of the total ion current. Deuterium-labeled 1-O-hexadecyl-2-(2H3)acetyl-sn-glycerophosphocholine is used as the internal standard for quantitation. The standard curves are linear and typically have a correlation coefficient of greater than 0.999. Using 1 pg of the deuterium-labeled internal standard, quantities as low as 100 fg are measured.