DETECTION OF ALKYLMETHYLPHOSPHONIC ACIDS ON LEAF SURFACES BY STATIC SECONDARY-ION MASS-SPECTROMETRY

Detection of environmental degradation products of nerve agents directly from the surface of plant leaves using static secondary ion mass spectrometry (SIMS) is demonstrated, Pinacolylmethylphosphonic acid (PMPA), isopropylmethylphosphonic acid (EMPA), and ethylmethyl-phosphonic acid (EMPA) were spiked from aqueous solutions onto philodendron leaves prior to analysis by static SIMS, Fragment ions were observed in the anion SIMS spectra from all three compounds at m/z 63, 77, 79, and 95, which are attributed to PO2-, CH2PO2-, PO3-, and CH3PO2OH-, respectively, Additionally, peaks due to [M - H](-) were observed at m/z 179 for PMPA, m/z 137 for IMPA, and m/z 123 for EMPA. The minimum detection limits for PMPA and IMPA on philodendron leaves were estimated to be between 4 and 0.4 ng/mm(2), The minimum detection limit for EMPA on philodendron leaves was estimated to be between 40 and 4 ng/mm(2), SIMS analyses of IMPA adsorbed on 10 different crop leaves were also performed in order to investigate the general applicability of static SIMS for detection of alkylmethylphosphonic acids (AMPAs) on a wide variety of leaves, Interferences due to organophosphorus pesticides were investigated as well as the effect of AMPA solution pH, The results of the work reported here suggest that static SIMS is a promising approach for rapid screening of organic surface contaminants on plant leaves.