MALDI for Polymer Analysis: Synthetic Polymers and Additives
Introduction:
A high-resolution MALDI/TOF-TOF system with unique ion optics is applied to the identification of polymers and polymer additives. Exact mass measurements and isotopic abundances were used to identify elemental compositions. High-energy collision-induced dissociation with monoisotopic precursor selection provided structural information for additives and polymers. The mass accuracy for the sodiated molecule of Irganox 1010 in polymethyl methacrylate (PMMA) was within 1ppm of the calculated m/z (m/z 1199.7733, C73H108O12Na+). The high-energy CID product-ion mass spectrum for sodiated Irganox 1010 shows bond cleavage with little or no rearrangement. Four types of product ions are identified for the high-energy CID product-ion mass spectra of sodiated PMMA ions.
Experimental:
Samples were analyzed by using a MALDI/TOF-TOF (JEOL JMS-S3000 “Spiral TOF™ MS”) mass spectrometer with multi-turn ion optics that fit a 17-meter flight path within a 1 meter space. Electrostatic sectors are used to continuously refocus the ion beam to minimize ion losses.
The MS-I resolving power is sufficiently high (60,000 FWHM) that monoisotopic precursor selection can be achieved by using a simple deflector. Ions with 20 keV kinetic energies undergo collisions with helium and a 9 keV post-acceleration combined with an offset parabolic reflector provides a wide energy acceptance for product ions.
Irganox1010 added to PMMA solution was used as a model sample, which included 5000 ppm as concentration of Irganox1010. 2,5-Dihydroxybenzoic acid (DHB) was used as the MALDI matrix and sodium iodide (NaI) was used as cationization agent.