大气压离子化质谱技术研究N-聚氧乙烯醚衍生物

利用大气压离子化质谱技术 ,采用直接进样方式研究了N 聚氧乙烯醚衍生物的氧乙烯链聚合度 (EO数 )分布 ,并对O 聚氧乙烯醚衍生物及壬基酚聚氧乙烯醚进行了测定。当化合物的分子质量小于 1 0 0 0u时 ,采用大气压化学离子源和大气压电喷雾离子源两种离子化质谱技术均可得到正态的EO数分布曲线 ,最大n值与根据环氧乙烷加入量计算出的平均加成数基本吻合。采用直接进样质谱技术可同步分析含氧乙烯链的不同结构化合物的EO数分布曲线。选择大气压化学离子源检测时 ,样品与溶剂间的极性差异越小越好 ;而采用大气压电喷雾离子源时 ,溶剂极性对EO数的正态分布影响较小。对于EO数较大的化合物 ,宜采用大气压电喷雾源离子化 ,并可观察到多电荷体系 ;调节质谱参数将影响多电荷体系的分布。直接进样质谱技术为含氧乙烯链化合物的EO数分布提供了一条快速、简捷的分析途径。

Study of N-Polyoxyethylene Derivatives with Atmospheric Pressure Ionization Mass Spectrometry Techniques

N Polyoxyethylene derivatives possess a molecular weight distribution as the different polymerization degrees(n) of ethylene oxide.With atmospheric pressure ionization(API) mass spectrometry technique,eight N polyoxyethylene derivatives having different numbers of ethoxy units are investigated by injecting samples directly,and this procedure was employed for some commercial surfactants,such as nonylphenol polyethoxylates.When the molecular weight of these compounds is less than 1000 dalton,the molecular weight distribution curves could be determined with both atmospheric pressure chemical ionization(APCI) and atmospheric pressure electrospray ionization(API-ES),the maximum value of n EO approximated to the average number of ethoxylate groups which was calculated according to the added quantity of ethylene oxide in synthesis.This method was also available to the simultaneous determination of mixture with different structure.Similar polarities of sample and solvent were expected in using APCI,but effect of solvent polarity on the ethylene oxide distribution curves was limited with API-ES.API-ES was suitable for determination of the compounds with large n EO numbers, and the double charged system was observed.The results show that API-MS technique is a very sensitive and rapid analytical procedure for the determination of n EO distribution and polymerization degrees of ethylene oxide.