SYSTEMATIC STUDY OF THE EFFECTS OF EXPERIMENTAL PARAMETERS ON THE BEAM-INDUCED DEHALOGENATION OF CHLORPROMAZINE IN LIQUID SECONDARY-ION MASS-SPECTROMETRY

The effect of experimental parameters such as time of irradiation, ana lyte concentration, primary beam density, matrix selection and matrix additives on the beam-induced dehalogenation of chlorpromazine in liqu id secondary ion mass spectrometry (LSIMS) was investigated. It was fo und that dehalogenation of chlorpromazine in glycerol increased with i ncreasing time of irradiation, analyte concentration and primary beam density. These results were compared with those obtained using 4-chlor ophenylalanine ethyl ester and the differences observed were rationali zed in terms of compound surface activity. Evidence is given that matr ix selection is the key experimental parameter affecting the extent of beam-induced dehalogenation of chlorpromazine in LSIMS, Of the eleven matrices used, the greatest extent of dehalogenation was observed in glycerol. Sulfur-containing matrices consistently exhibited a lower ex tent of dehalogenation than oxygen-containing aliphatic matrices, impl ying that sulfur is implicated in mitigating the reduction process. De halogenation was totally inhibited in 2-hydroxyethyl disulfide, 4-hydr oxybenzenesulfonic acid and 3-nitrobenzyl alcohol. Similarly, the use of matrix additives such as 3-nitrobenzyl alcohol and trifluoroacetic acid was found to be useful in inhibiting the extent of dehalogenation occurring in glycerol.