Delcorte A, Bertrand P
Unité de Physico-Chimie et de Physique des Matériaux, Université catholique de Louvain, 1 Croix du Sud, B-1348, Louvain-la-Neuve, Belgium.
Anal Chem. 2005 Apr 1;77(7):2107-15. doi: 10.1021/ac040158s.
In a search for molecular ion signal enhancement in organic SIMS, the efficiency of a series of organic and inorganic salts for molecular cationization has been tested using a panel of nonvolatile molecules with very different chemical characteristics (leucine enkephalin, Irganox 1010, tetraphenylnaphthalene, polystyrene). The compounds used for cationization include alkali bromide and group Ib metal salts (XBr with X = Li, Na, K; CF3CO2Ag; AgNO3; [CH3COCH=C(O-)CH3]2Cu; AuCl3). Alkali ions, very good for polar molecule cationization, prove to be of limited interest for nonpolar molecules such as polystyrene. Silver trifluoroacetate displays excellent results for all the considered molecules, except for leucine enkephalin (which might be due to the use of different solvents for the analyte and the salt). Instead, silver nitrate mixed with leucine enkephalin in an ethanol solution provides intense molecular signals. The influence of the respective concentrations of analyte and salt in solution, of the silver trifluoroacetate solution stability, and of the sample microstructure on the secondary ion intensities are also investigated. The results of other combinations of analyte and salts are reported. Finally, the use of salts is critically compared to other sample preparation procedures previously proposed for SIMS analysis of large organic molecules.
为了在有机二次离子质谱（SIMS）中寻找分子离子信号增强的方法，我们使用了一组具有非常不同化学特性的非挥发性分子（亮氨酸脑啡肽、抗氧剂1010、四苯基萘、聚苯乙烯），测试了一系列有机和无机盐用于分子阳离子化的效率。用于阳离子化的化合物包括碱金属溴化物和第Ib族金属盐（XBr，其中X = Li、Na、K；CF3CO2Ag；AgNO3；[CH3COCH = C(O-)CH3]2Cu；AuCl3）。碱金属离子对极性分子阳离子化非常有效，但对于聚苯乙烯等非极性分子来说，其作用有限。三氟乙酸银对所有考虑的分子都显示出优异的结果，但亮氨酸脑啡肽除外（这可能是由于对分析物和盐使用了不同的溶剂）。相反，硝酸银与亮氨酸脑啡肽在乙醇溶液中混合可提供强烈的分子信号。还研究了溶液中分析物和盐的各自浓度、三氟乙酸银溶液稳定性以及样品微观结构对二次离子强度的影响。报告了分析物和盐的其他组合的结果。最后，将盐的使用与先前提出的用于大型有机分子SIMS分析的其他样品制备程序进行了严格比较。
