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Analysis of low molecular weight polyethylene with solvent-free method using JMS-S3000 "SpiralTOF™"

Product: JMS-S3000

Introduction

Matrix assisted laser desorption ionization (MALDI) time-flight mass spectrometer (TOFMS) is a powerful tool to identify the repeat units and end groups of polymers. The mass spectra of polymers can be easily interpreted because MALDI can generate singly-charged ions over a wide mass range. MALDI is a soft ionization method that uses "matrix" compounds and “cationization agents” to assist the ionization process of polymers. Typically, sample, matrix and cationization agent are dissolved in the same solvent. These solutions are pre-mixed and placed drop-wise on the target plate to make cocrystals (dried droplet method). However, this procedure cannot be applied to polymers that are insoluble or only slightly soluble. To solve this problem, solvent-free methods have been developed [1-4] for these situations. In this report, we analyzed low molecular weight polyethylene by using a solvent-free method and then using a high mass-resolution MALDI-TOFMS “SpiralTOF™” system for the analysis.

Experimental

Sample: Polyethylene analytical standard, for GPC, 1,000
(Sigma Aldrich, PN 81219) (PE1000)

Matrix: trans-2-[3-(4-tert-Butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB)

Cationization Agent: Silver Trifluoroacetate (AgTFA)

Preparation: PE1000, DCTB and AgTFA powders were mixed in Agate mortar. The mixed powder was then pressed onto the target plate using a spatula (Note 1). (See Figure 1)

Measurement: The mass spectra were acquired by using SpiralTOFTM positive ion mode.

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