基于电感耦合等离子体串联质谱(ICP-MS/MS)建立了准确测定丙二醇甲醚中超痕量金属杂质元素的分析方法, 提出了利用混合反应气消除质谱干扰的新策略。 丙二醇甲醚经超纯水稀释后直接采用ICP-MS/MS测定其中具有挑战性的超痕量金属元素Mg, Al, K, Ti, V, Cr, Fe, Ni, Cu和Zn, 在MS/MS模式下, 选择混合气NH₃/He/H₂为反应气, Ti⁺, Cr⁺, Fe⁺, Ni⁺, Cu⁺, Zn⁺与NH₃发生质量转移反应, 在形成的团簇离子中, Ti(NH₃)6+, Cr(NH₃)2+, Fe(NH₃)2+, Ni(NH₃)3+, Cu(NH₃)2+和Zn(NH₃)⁺丰度高且无干扰, 利用NH₃质量转移法将Ti⁺, Cr⁺, Fe⁺, Ni⁺, Cu⁺和Zn⁺转移为相应的团簇离子进行测定; H₂能与加合物—NH和—NH₂反应生成—NH₃, 增大碰撞/反应池(CRC)内—NH₃的浓度, 有利于提高Ti, Cr, Fe, Ni, Cu和Zn的分析灵敏度。 Mg⁺, Al⁺, K⁺和V⁺几乎不能与NH₃反应, 而干扰离子能与NH₃反应形成团簇离子, 可以利用NH₃原位质量法进行Mg, Al, K, V的测定; H₂能快速与Ar基干扰离子发生反应, 而与其他离子的反应速度很慢, 反应气中加入H₂能迅速彻底消除Ar基干扰离子所形成的质谱干扰, 有利于Mg, Al, K和V的测定。 优选Sc⁺与NH₃反应生成的团簇离子Sc(NH₃)5+为Ti(NH₃)6+, Cr(NH₃)2+, Fe(NH₃)2+, Ni(NH₃)3+, Cu(NH₃)2+和Zn(NH₃)⁺的内标离子, Be⁺与NH₃反应生成的团簇离子Be(NH₃)4+为Mg⁺, Al⁺, K⁺和V⁺内标离子, 校正了样品溶液, 标准溶液和空白溶液之间由于物理化学性质差异产生的基体效应, 确保了分析信号的稳定。 将所建立的方法应用实际样品的加标回收实验, 并采用双聚焦扇形磁场电感耦合等离子体质谱(SF-ICP-MS)进行对比分析, 评价分析方法的准确性。 结果表明, 各元素的检出限为0.52~61.5 ng·L^-1, 加标回收率为95.6%~104.2%, 相对标准偏差(RSD)≤4.5%; 在95%的置信度水平, 所有元素的分析结果与SF-ICP-MS的测定结果无显著性差异, 验证了分析方法的准确性好, 精密度高。 将方法应用于丙二醇甲醚中超痕量金属杂质元素的测定, 具有分析速度快, 无干扰, 灵敏度高的优势。

Based on inductively coupled plasma tandem mass spectrometry (ICP-MS/MS), an analytical method for the accurate determination of ultra-trace metal impurity elements in propylene glycol methyl ether (PGME) was established, and mixed reaction gas was used to eliminate the spectral interference. The challenging ultra-trace metal elements including Na, Mg, Al, Ti, V, Cr, Fe, Ni, Cu, and Zn in diluted PGME were determined directly by ICP-MS/MS. In the MS/MS mode, the mixed gas NH₃/He/H₂ was selected as the reaction gas. Ti⁺, Cr⁺, Fe⁺, Ni⁺, Cu⁺, Zn⁺ and NH₃ undergo mass shift reactions. Among the large number of cluster ions formed, Ti(NH₃)6+, Cr(NH₃)2+, Fe(NH₃)2+, Co(NH₃)2+, Ni(NH₃)3+, Cu(NH₃)2+, Zn(NH₃)⁺ have high abundances and interference-free, Ti⁺, Cr⁺, Fe⁺, Ni⁺, Cu⁺, Zn⁺ can be transferred to the corresponding cluster ions for determination by NH₃ mass shift method. H₂ can react with the adducts —NH and —NH₂ to form —NH₃. Increasing the concentration of —NH₃ in the collision/reaction cell (CRC) will help to improve the analytical sensitivity of Ti, Cr, Fe, Ni, Cu, Zn. Mg⁺, Al⁺, K⁺, V⁺ can hardly react with NH₃, and the interference ions can react with NH₃ to form cluster ions. The NH₃ on-mass method can be used to determine the contents of Mg, Al, K, and V. Argide ions react with H₂ at a relatively fast rate, while nearly all elemental ions exhibit low reactivity with H₂. Therefore, the addition of H₂ to the reaction gas can quickly and completely eliminate the spectral interference caused by Argide ions, which is beneficial to the determination of Mg, Al, K, and V. The cluster ions Sc(NH₃)5+ generated by the reaction between Sc⁺ and NH₃ were selected as the standard internal ions of Ti(NH₃)6+, Cr(NH₃)2+, Fe(NH₃)2+, Ni(NH₃)3+, Cu(NH₃)2+, and Zn(NH₃)⁺. The cluster ions Be(NH₃)4+ generated by the reaction between Be⁺ and NH₃ were selected as the standard internal ions of Mg⁺, Al⁺, K⁺, and V⁺. The matrix effect caused by the difference of physical and chemical properties between sample solution, standard solution and the blank solution was corrected to ensure the stability of the analytical signal. The developed method was applied to the spike recovery experiment of real samples, and the accuracy was evaluated by comparing and analyzing with sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). The results show that the limit of detection is 0.52~61.5 ng·L^-1, the spiked recovery is 95.6%~104.2%, and the relative standard deviation (RSD) is ≤4.5%. At the 95% confidence level, there is no significant difference between the analysis results of analytes and that of SF-ICP-MS, which verifies the accuracy and precision of this analysis method. The method shows great potential for determining the ultra-trace metal impurity elements in PGME, and has the advantages of rapid, interference-free and high sensitivity.