Electron capture negative ion chemical ionization analysis of arachidonic acid

A highly sensitive (subpicomole level) and structural specific method for the analysis of arachidonic acid esterified to complex glycerophospholipids has been developed using combined capillary gas chromatography and mass spectrometry. The methodology is based upon the formation of the pentafluorobenzyl ester of arachidonic acid, which is efficiently ionized using electron capture negative ion chemical ionization conditions to yield an abundant carboxylate anion at m/z 301. Quantification is carried out following hydrolysis of the complex glycerophospholipid in the presence of a known amount of (2H8) arachidonic acid. The use of this method is illustrated by the quantification of arachidonic acid within the glycerophospholipid classes isolated from resident peritoneal macrophage cells isolated from HS mice.