Small Angle Neutron Scattering Measurements of Snythetic Polymer Dispersions in Matrix-Assisted Laser Desorption/Ionization Matrixes
Barry J. Bauer, H M. Byrd, Kathleen M. Flynn
Small angle neutron scattering (SANS) is used to measure the size and the dispersion of synthetic polymers in matrix-assisted laser desorption/ionization (MALDI) matrixes. Deuterated polystyrene (DPS) and dithranol in tetrahydrofuran were deposited by electrospray onto a substrate for small angle neutron scattering (SANS) measurements. DPS with (6,050 and 27,000) g mol-1 molecular masses were prepared at mass fractions between (0.2 and 6) %. All samples contained large aggregates of DPS with characteristic sizes > 200 that represent hundreds of aggregated chains. Samples of mass fraction 1 % DPS (6,050 g mol-1) in 2,5-dihydroxy benzoic acid, all-trans retinoic acid, and sinapinic acid also have large zero angle scattering characteristic of large aggregates. The morphological trend obtained from the SANS measurements of the DPS aggregate size in the four matrixes is dithranol > 2,5-dihydroxybenzoic acid > all-trans-retinoic acid > sinapinic acid. These measurements indicate that DPS in dithranol exhibits the most strong phase separation, while DPS in sinapinic acid shows considerable domain mixing.All of these matrixes produce MALDI signal strength under appropriate conditions, suggesting that strong phase separation does not diminish the signal-to-noise ratio. DPS (188 000 g mol-1) in biphenyl was used as a model system of a matrix that can be either crystalline or amorphous. SANS data shows that above the biphenyl melting point, a conventional solution is formed that has molecularly dispersed polymers. Upon crystallization, there is strong aggregation of the DPS into large domains. Therefore, the crystalline matrixes commonly used in MALDI measurements probably cause large aggregations of polymers to be present during the MALDI process.
, Byrd, H.
and Flynn, K.
Small Angle Neutron Scattering Measurements of Snythetic Polymer Dispersions in Matrix-Assisted Laser Desorption/Ionization Matrixes, Rapid Communications in Mass Spectrometry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852007
(Accessed December 11, 2023)