酸性染料在四极杆/静电场轨道阱高分辨质谱中的离子化与裂解规律

Study on the Ionization and Fragmentation Law of Acid Dyes by Quadrupole/ Electrostatic Field Orbitrap High Resolution Mass Spectrometry

采用四极杆/静电场轨道阱高分辨质谱(Q-Orbitrap-HRMS),对结构性质差异大的常见18种酸性染料的分子离子峰存在形式进行研究,并在分辨率高达70 000条件下,直接采集准分子离子峰碎裂片段的高精度质量数(分辨率>70 000,m/z 200),通过元素模拟得到碎片离子的元素组成,进而探究酸性红1、酸性蓝9和酸性红18的裂解规律。结果表明:该类染料的分子离子峰是通过丢掉全部Na+离子后,自身形成带负电荷离子,以其中含有多个磺酸基(SO-3)的二价准分子离子为基峰;随着能量增加,裂解过程主要集中在化合物支链单键上,其中偶氮基团结构存在叠氮-偶氮的互变异构体,高键能的偶氮键■重排为氮氮单键(-NH-■)后,易发生C-N键和-NH-■键的断裂,同时伴随小分子的中性丢失,产生m/z 79.955 7(SO-3离子)的特征碎片离子。此外,通过直接进样确定18种酸性染料的最佳电离方式和分子离子峰存在形式,得到酸性红1、酸性蓝9和酸性红18的质谱裂解规律,可为相似染料的电喷雾质谱行为解析提供参考。

The existence forms of molecular ion peaks of 18 acid dyes with different structures and properties,and the high accuracy mass number of fragmentation fragments(resolution>70 000,m/z 200) were studied by quadrupole/electrostatic field orbitrap high resolution mass spectrometry(Q-Orbitrap-HRMS),and the element composition was obtained by element simulation,and then the cracking laws of acid red 1,acid blue 9 and acid red 18 were investigated.Results showed that the molecular ion peaks of these dyes were changed into negatively charged ions by removing all Na ions,in which the bivalent excimer ions with multiple sulfonic groups(SO-3) were the base peaks.With the increase of energy,the fracture process mainly concentrated on the single bond of compound branch chain,in which a tautomer of azido-azo existed in the azo group structure,the azo bond■ of the high-bond energy was rearranged into a nitrogen-nitrogen single bond(-NH-■,and the C-N bond and -NH-■bond were easily broken.While with the neutral loss of the small molecule,the characteristic fragment ion of m/z 79.955 7(SO-3) was generated.The optimum ionization modes and the existence forms of molecular ion peaks of 18 acid dyes were determined by direct injection.The mass spectrometry cracking law for acid red 1,acid blue 9 and acid red 18 provides a reference for the analysis of electrospray ionization mass spectrometry behaviors of similar dyes.