对位芳纶端基结构分析的MALDI-TOF MS方法的建立与优化

Establishment and Optimization of MALDI-TOF MS Method for Poly(p-Phenylene Terephthalamide) End Group Analysis

采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)对对位芳纶的端基结构进行分析。以3-氨基喹啉为基质,三氟乙酸钾为离子化剂,采用蒸发研磨法(E-G)制备了测试样;为了获得具有较高信噪比的对位芳纶MALDI-TOF MS图,对基质与分析物比例进行优化,重点分析了少量残余硫酸对质谱结果的影响。结果表明:在反射模式下,样品制备选择基质/分析物比例为20:1可获得较佳的质谱信号;样品中含有少量硫酸能够改善分析物与基质的结晶效果,减少脱羧作用的发生,降低氨基碎片丢失的几率,使得H/Na和H/K交换现象发生的几率降低,从而改善质谱信噪比,提高分析可靠性。

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（MALDI-TOF MS） was used to analyze the end-group distribution of poly（p-phenylene terephthalamide）（PPTA）.Samples were prepared by the evaporation-grinding（E-G） method.In order to improve the grinding of PPTA,the samples were treated with concentrated sulfuric acid until they became soft before the sample preparation.3-Aminoquinoline was employed as the matrix material with potassium trifluoroacetate as the cationizing agent.The ratio of matrix-to-polymer was optimized in order to achieve higher signal-to-noise ratio.The MALDI-TOF MS spectrum of the sample with residual sulfuric acid was compared with the MS spectra of the sample without residual sulfuric acid,the influence of residual traces of sulfuric acid on the MALDI-TOF MS spectra was analyzed.The results showed that a relatively higher signal-to-noise ratio was obtained at the matrix-to-polymer mixing ratio of 20∶1 in the reflection mode.The peak splitting from hydrogen/sodium and hydrogen/potassium exchange,the amino-group fragment loss and decarboxylation probability were also reduced by the residual traces of sulfuric acid in the samples,which could improve the signal-to-noise ratio and reliability.