Investigations of matrix-assisted laser desorption/ionization sample preparation by time-of-flight secondary ion mass spectrometry

Matrix-assisted laser desorption/ionization (MALDI) and time-of-flight seco ndary ion mass spectrometry (ToF-SIMS) analyses are compared to gain insigh t into some of the details of sample preparation for MALDI analysis of synt hetic polymers. ToF-SIMS imaging of MALDI samples shows segregation of the cationization agent from the matrix crystals. The amount of observed segreg ation can be controlled by the sample preparation technique. Electrospray s ample deposition minimizes segregation. Comparing ToF-SIMS and MALDI mass s pectra from the same samples confirms that ToF-SIMS is significantly more s urface sensitive than MALDI. This comparison shows that segregation of the oligomers of a polymer sample can occur during MALDI sample preparation. Ou r data indicate that MALDI is not as sensitive to those species dominating the sample surface as to species better incorporated into the matrix crysta ls. Finally, we show that matrix-enhanced SIMS can be an effective tool to analyze synthetic polymers, although the sample preparation conditions may be different than those optimized for MALDI. (J Am Soc Mass Spectrom 1999, 10, 104-111) (C) 1999 American Society for Mass Spectrometry.