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实时直接分析电离源(DART)已经广泛应用于固体、液体和气体样品的快速检测.在使用DART对低挥发性化合物进行分析时,样品衍生化是十分重要的.四甲基氢氧化铵(TMAH)是强的瞬时甲基化试剂,常用于GC-MS的分析中.以人参皂苷及人参寡糖为例,研究了它们在TMAH的辅助下在DART中发生甲基化及电离的过程,并从凝聚相和气相的角度对电离过程中的甲基化机理进行了研究.人参皂苷主要发生不完全和全甲基化,人参寡糖的甲基化则随着糖链的增长以及羟基的增多由全甲基化主导转变为过甲基化主导.结果表明,凝聚相和气相的共同作用是质谱检测到甲基化及过甲基化样品分子的根本原因.
Real-time Direct Analysis Ionization Sources (DARTs) have been widely used for the rapid detection of solid, liquid and gas samples. Sample derivatization is important when analyzing low volatility compounds using DART. Tetramethylammonium hydroxide (TMAH ) Is a strong transient methylation reagent commonly used in the analysis of GC-MS.Ginsenosides and ginseng oligosaccharides, for example, to study their methylation and ionization in DART assisted by TMAH, and The mechanism of methylation in ionization process was studied from the perspective of coacervate phase and gas phase.Ginsenosides mainly occurred incomplete and full methylation.The methylation of ginseng oligosaccharides with the increase of sugar chain and the increase of hydroxyl groups The results showed that the co-action of condensed phase and gas phase is the fundamental reason for the detection of methylated and over-methylated sample molecules by mass spectrometry.