ENHANCEMENT OF ION INTENSITY IN TIME-OF-FLIGHT SECONDARY-IONIZATION MASS-SPECTROMETRY

Enhancement of ion intensity in static secondary-ionization mass spect rometry (SIMS) has been achieved by using a matrix-assisted sample pre paration technique. Previous investigations of polymers and biomolecul es by SIMS indicated that secondary-ion (SI) yield is dependent on sub strate coverage. Recently we discovered a sample preparation technique that enhanced the SI yield of cyclosporin A (CsA) in an allograft pat ient sample and neat samples of CsA (1202 rr) and polystyrene (M(w) = 2650 u). The preparation technique involves deposition of a submonolay er of cocaine hydrochloride (5 mu L of a 20-mu g/mL MeOH solution) on an etched silver substrate, solvent evaporation, and subsequent deposi tion of the analyte. This preparation method resulted in similar to 30 0% increase in the SI yield of CsA and polystyrene when deposited from neat solutions. The original discovery was observed when a blood extr act that contained CsA was deposited on an etched Ag substrate that ha d been soaking in a dilute cocaine solution for similar to 2 months. I n these initial experiments, the SI yield of CsA was enhanced by over 1 order of magnitude.