Determination of pyrethroid insecticides by ion trap GC-MS-MS

Selected ejection isobutane chemical ionization (SECI) of pyrethroid insecticides was compared to collisionally activated dissociation (CAD) of selected ions by using a benchtop quadrupole ion trap mass spectrometer. SECI-CAD was successfully demonstrated for compounds of different masses which elute closely. SECI produced a characteristic cleavage at the ester bond for most compounds, while SECI-CAD of the protonated species showed this cleavage as well, but with a reduced number of different fragment ions for the higher mass pyrethroids. The limit of detection showed a loss of one order of magnitude during the isolation step of the ions followed by a loss of half or none of the ion intensity during the activation step. Typical detection limits were in the ppb range.