title: Application of parylene for surface (polymer) enhanced laser desorption/ionization of synthetic polymers.
abstract: BACKGROUND
  Synthetic polymers of molecular masses up to a few kDa can be analyzed without the use of any matrix by direct laser desorption/ionization mass spectrometry (LDI-MS). In this technique, the surface of the sample plate plays a crucial role, and many attempts have been made to understand the influence of the surface on the ease of desorption. Since this technique requires no tedious sample pretreatment, it is a promising method for the rapid characterization of various synthetic polymers.
  
  
  METHODS
  Parylene (poly(p-xylylenes), PPX) was tested as a surface support for studying the molecular masses of biocompatible polymers: poly(ethylene glycol) (PEG), poly(L-lactide) (PLLA), and poly(methyl methacrylate) (PMMA). The average molecular masses of the polymers were: PEG (600.0 Da and 3.5 kDa), PMMA (2.0 kDa), and PLLA (2.8 kDa).
  
  
  RESULTS
  LDI mass spectra of polymers deposited on parylene were enhanced by a factor of two over those obtained directly from the gold target plate.
  
  
  CONCLUSIONS
  Modification of the surface of the target plate by the addition of a PPX layer extended the functionality of LDI-TOF MS, especially for the analysis of low-mass compounds. The LDI analysis using the PPX-coated target plate provided details of polymers including: end-group, composition, monomer unit, and molecular mass distribution. The average molecular weights of four tested polymers on the gold target plate and the PPX support were unchanged, indicating that sample degradation was not occurring despite the high energy of the laser beam. The LDI investigations showed that the PPX support boosted ion yields by a factor of two compared with the gold target plate.
authors.affiliation: Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363, Lodz, Poland. miksa@cbmm.lodz.pl
authors.forename: Beata J
authors.initials: BJ
authors.lastname: Miksa
authors.forename: Marek
authors.initials: M
authors.lastname: Sochacki
authors.forename: Anna
authors.initials: A
authors.lastname: Sroka-Bartnicka
authors.forename: Paweł
authors.initials: P
authors.lastname: Uznański
authors.forename: Andrzej
authors.initials: A
authors.lastname: Nosal
authors.forename: Marek J
authors.initials: MJ
authors.lastname: Potrzebowski
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*; D013499:Surface Properties; D014867:Water / Q000737:chemistry; D014992:Xylenes / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D011108:Polymers; D014992:Xylenes; D014867:Water; C011055:parylene; D006046:Gold