Analytical Sciences

Laser Desorption/Ionization on Porous Silicon Mass Spectrometry for Accurately Determining the Molecular Weight Distribution of Polymers Evaluated Using a Certified Polystyrene Standard

Teruyuki SEINO,*^,** Hiroaki SATO,** Masaki TORIMURA,** Kazue SHIMADA,*** Atsushi YAMAMOTO,*** and Hiroaki TAO**

*New Energy and Industrial Technology Development Organization (NEDO), 1310 Omiya, Saiwai, Kawasaki 212-8554, Japan
**Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan
***Research Institute for Energy Electronics, AIST, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan

Desorption/ionization on porous silicon-mass spectrometry (DIOS-MS) is a novel soft ionization MS technique that does not require any matrix reagent, ideally resulting in fewer obstructive peaks in the lower mass region. In this study, the etching conditions of porous silicon spots as an ionization platform of DIOS-MS were investigated for determining the molecular weight distribution (MWD) of polymers. To evaluate the accuracy of DIOS mass spectra observed using porous silicon spots prepared under various etching conditions, a certified polystyrene (PS) standard sample with an average molecular weight of ca. 2400 was used as a model sample. By optimizing the etching conditions, the MWD of the PS sample could be accurately observed by DIOS-MS using both p-type and n-type porous silicon spots. Especially, in the case of a suitable n-type spot, an accurate peak distribution with very fewer obstructive background peaks could be observed using the minimum laser power, comparable to the conventional matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS).

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