Improved methodology for liquid chromatography/continuous flow secondary-ion mass spectrometry: Quantitation of abscisic acid glucose ester using reaction monitoring

Improvements in methodology for liquid chromatography/continuous flow secondary‐ion mass spectrometry (LC/CFSIMS) are described. Practical procedures have been developed for the preperation of packed fusedsilica capillary liquid chromatography columns and the coupling of these columns to the CFSIMS probe. A modified probe tip is described that significantly reduced ion beam instability arising from acceleration voltage discharge, changes in mobile phase composition during gradient elution, and uneven tip wettability. Interfering matrix background ions in LC/CFSIMS experiments are eliminated by reaction monitoring: the detection limit of the plant hormone metabolite, abscisic acid glucose ester, ABAGE is below 100 pg (235 fmol) with this technique. Reproducibility for quantitation is achieved by parallel reaction monitoring of the analyte and an added internal standard, ABAGE‐d6. The d6/d0 ABAGE response ratio for the monitored transitions is linear over the range 100 pg to 10 ng of injected ABAGE.