Microbore liquid chromatography–electrospray mass spectrometry of selected synthetic pyrethroid insecticides

Abstract

The pyrethroid insecticides kadethrin, α-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 α-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.