Microbore liquid chromatography electrospray mass spectrometry of selected synthetic pyrethroid insecticides

The pyrethroid insecticides kadethrin, alpha-cypermethrin, flucythrinate and SSI-116 have been studied by positive-ion electrospray mass spectrometry (+ESMS) in the presence of ammonium acetate and formic acid. Ammoniated molecule base peak ions [M + NH4](+) were observed for all the insecticides studied at low electrospray source sampling cone voltages. The effect of increasing the cone voltage (40-120 V) and its influence on the extent of fragmentation experienced by each insecticide were studied. A number of these key fragment ions found in +ESMS spectra of alpha-cypermethrin have been examined by MS-MS under low-energy collisional activation (CA) conditions. On-line microbore reversed-phase liquid chromatographic separations were performed on mixed pyrethroid standards. The eluates were analysed by +ESMS to establish the lower limits of detection using full-scan and selective-ion recording (SIR) modes. Limits of detection (signal-to-noise ratio better than 3:1) for each component of the pyrethroid mixture, injected on column, were in the range 120-300 pg (0.30-0.77 pmol) using full-scan mode and 12-60 pg (0.03-0.15 pmol) by SIR.