A DIRECT DEPOSITION METHOD FOR COUPLING MATRIX-ASSISTED LASER DESORPTION IONIZATION MASS-SPECTROMETRY WITH GEL-PERMEATION CHROMATOGRAPHY FOR POLYMER CHARACTERIZATION/

Matrix-assisted laser desorption/ionization (MALDI) measurements of po lymeric materials of narrow polydispersity provide molecular weight me asurements that agree closely with those from conventional tools such as gel-permeation chromatography (GPC). However, materials that have a broader molecular weight distribution (polydispersity) > 1.1) have be en shown to diminish the accuracy of the MALDI results. In a recent ef fort to overcome this limitation, some researchers have utilized GPC p rior to MALDI analysis to collect fractions with narrower molecular we ight distributions. In our research, the GPC eluent was spray deposite d onto a rotating matrix-coated substrate and the resulting polymer 't rail' was characterized directly by MALDI. Specifically, molecular wei ght information was determined using various points along poly(methyl methacrylate) sample 'trails' deposited on a matrix of trans-3-indolea crylic acid. The overall number-average molecular weight (M-n) and mol ecular weight distribution (MWD) for each of the samples were calculat ed The M-n values are in fairly good agreement with manufacturer's val ues, though the MWD values determined by MALDI are narrower. (C) 1997 by John Wiley & Sons, Ltd.