IMPROVEMENT OF SIGNAL INTENSITIES IN STATIC SECONDARY-ION MASS-SPECTROMETRY USING HALIDE ADDITIVES AND SUBSTRATE MODIFICATION

A new approach is reported for secondary-ion time-of-flight mass spect rometry (TOF-SIMS) sample preparation. The method involves the use of halide additives or halide modification of silver substrate surfaces t o promote analyte cationization and protonation. The enhancement of si gnal intensity has been demonstrated for neutral organic lipophilic an d hydrophilic compounds including various small peptides and nucleosid es. Improvement factors range from 2-30 for cationized species to 20-2 000 for protonated species. However, the new sample preparation does n ot affect the signal intensities of preformed ionic species. The sampl e preparation approach is applicable to a wide variety of neutral comp ounds and should find broad use for organic analysis by TOF-SIMS. (C) 1998 John Wiley & Sons, Ltd.