Laser desorption ionization and MALDI time-of-flight mass spectrometry for low molecular mass polyethylene analysis

• Published in: Journal of the American Society for Mass Spectrometry 2001-11, Vol.12 (11), p.1186-1192
• Main Authors: Chen, Rui, Yalcin, Talat, Wallace, William E., Guttman, Charles M., Li, Liang
• Format: Article
• Language: English
• Subjects: Alkanes; Alkenes; Desorption; Fragmentation; Indicators and Reagents; Ionization; Ions; Laser beams; Lasers; Mass spectrometers; Mass spectrometry; Molecular Weight; Polyethylene; Polyethylenes; Polyethylenes - analysis; Silver; Spectrometers; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/S1044-0305(01)00308-7

Polyethylene’s inert nature and difficulty to dissolve in conventional solvents at room temperature present special problems for sample preparation and ionization in mass spectrometric analysis. We present a study of ionization behavior of several polyethylene samples with molecular masses up to 4000 Da in laser desorption ionization (LDI) time-of-flight mass spectrometers equipped with a 337 nm laser beam. We demonstrate unequivocally that silver or copper ion attachment to saturated polyethylene can occur in the gas phase during the UV LDI process. In LDI spectra of polyethylene with molecular masses above ∼1000 Da, low mass ions corresponding to metal–alkene structures are observed in addition to the principal distribution. By interrogating a well-characterized polyethylene sample and a long chain alkane, C 94H 190, these low mass ions are determined to be the fragmentation products of the intact metal–polyethylene adduct ions. It is further illustrated that fragmentation can be reduced by adding matrix molecules to the sample preparation.