School of Physics, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, Georgia 30332, USA.
Anal Chem. 2010 Jan 15;82(2):621-7. doi: 10.1021/ac901964m.
In this paper, we demonstrate the first use of a microplasma ionization source for ambient mass spectrometry. This device is a robust, easy-to-operate microhollow discharge that enables ambient direct analysis of gaseous, liquid, and solid-phase samples with minimum requirements in terms of operating power and high purity gas consumption. The initial performance of the microplasma device has been evaluated by ionizing samples containing dimethyl sulfoxide (DMSO), dimethylformamide (DMF), methyl salicylate, caffeine, l-leucine, l-histidine, loratadine, ibuprofen, acetaminophen, acetylsalicylic acid, and cocaine in various forms. These molecules are diverse in nature, but almost all have relatively high proton affinities. Thus, the major species observed in all obtained mass spectra corresponded to protonated molecules. Though these microplasmas are known to produce significant densities of metastable species and electrons with mean energies greater than several electronvolt, minimal fragmentation was observed. Background spectra showed prominent signals corresponding to H(+)(H(2)O)(2) ions and a distinct lack of H(3)O(+). Small water cluster ions are likely the dominant proton transfer agents, giving rise to mass spectral data very similar to that obtained using other plasma-based ambient ionization techniques. The simplicity, low cost, low power, low rate of gas consumption, and possibility of being batch-fabricated, makes these microplasma devices attractive candidates as ion sources for miniaturized mass spectrometry and other field detection applications.
在本文中，我们展示了微等离子体离子源在环境质谱中的首次应用。该装置是一种坚固、易于操作的微空心放电，能够在最小的操作功率和高纯气体消耗条件下，对气体、液体和固相样品进行环境直接分析。通过对含有二甲基亚砜（DMSO）、二甲基甲酰胺（DMF）、水杨酸甲酯、咖啡因、亮氨酸、组氨酸、氯雷他定、布洛芬、对乙酰氨基酚、乙酰水杨酸和可卡因等不同形式的样品进行电离，评估了微等离子体装置的初始性能。这些分子在性质上是多种多样的，但几乎都具有相对较高的质子亲和力。因此，在所有获得的质谱中观察到的主要物种都对应于质子化分子。尽管这些微等离子体已知会产生大量的亚稳态物质和具有超过几个电子伏特的平均能量的电子，但观察到的碎片化很少。背景光谱显示出与 H(+)(H(2)O)(2)离子对应的显著信号，以及明显缺乏 H(3)O(+). 小的水分子簇离子可能是主要的质子转移剂，产生的质谱数据与使用其他基于等离子体的环境电离技术获得的数据非常相似。由于其简单、低成本、低功耗、低气体消耗率以及批量制造的可能性，这些微等离子体装置作为微型化质谱和其他现场检测应用的离子源具有吸引力。
