Andrade Francisco J, Shelley Jacob T, Wetzel William C, Webb Michael R, Gamez Gerardo, Ray Steven J, Hieftje Gary M
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
Anal Chem. 2008 Apr 15;80(8):2654-63. doi: 10.1021/ac800210s. Epub 2008 Mar 18.
The flowing afterglow-atmospheric pressure glow discharge (APGD) ionization source described in part 1 of this study (in this issue) is applied to the direct analysis of condensed-phase samples. When either liquids or solids are exposed to the ionizing beam of the APGD, strong signals for the molecular ions of substances present on their surfaces can be detected without compromising the integrity of the solid sample structure or sample substrate. As was observed for gas-phase compounds in part 1 of this study, both polar and nonpolar substances can be ionized and detected by mass spectrometry. The parent molecular ion (or its protonated counterpart) is usually the main spectral feature, with little or no fragmentation in evidence. Preliminary quantitative results show that this approach offers very good sensitivity (detection limits in the picogram regime are reported for several test compounds in part 1 of this study) and linear response to the analyte concentration. Examples of the application of this strategy to the analysis of real-world samples, such as the direct analysis of pharmaceutical compounds or foods is provided. The ability of this source to perform spatially resolved analysis is also demonstrated. Preliminary studies of the mechanisms of the reactions involved are described.
本研究第1部分（本期）中描述的流动余辉-大气压辉光放电（APGD）电离源被应用于凝聚相样品的直接分析。当液体或固体暴露于APGD的电离束时，可以检测到其表面存在的物质的分子离子的强信号，而不会破坏固体样品结构或样品基质的完整性。正如在本研究第1部分中对气相化合物所观察到的那样，极性和非极性物质都可以被电离并通过质谱检测。母体分子离子（或其质子化对应物）通常是主要的光谱特征，几乎没有或没有碎片迹象。初步定量结果表明，这种方法具有非常好的灵敏度（本研究第1部分报告了几种测试化合物的皮克级检测限），并且对分析物浓度呈线性响应。提供了这种策略在实际样品分析中的应用实例，例如药物化合物或食品的直接分析。还展示了该源进行空间分辨分析的能力。描述了所涉及反应机制的初步研究。
