Waltman Melanie J, Dwivedi Prabha, Hill Herbert H, Blanchard William C, Ewing Robert G
Pacific Northwest National Laboratory, Richland, WA 99354, USA.
Talanta. 2008 Oct 19;77(1):249-55. doi: 10.1016/j.talanta.2008.06.014. Epub 2008 Jun 21.
A recently developed atmospheric pressure ionization source, a distributed plasma ionization source (DPIS), was characterized and compared to commonly used atmospheric pressure ionization sources with both mass spectrometry (MS) and ion mobility spectrometry (IMS). The source consisted of two electrodes of different sizes separated by a thin dielectric. Application of a high RF voltage across the electrodes generated plasma in air yielding both positive and negative ions. These reactant ions subsequently ionized the analyte vapors. The reactant ions generated were similar to those created in a conventional point-to-plane corona discharge ion source. The positive reactant ions generated by the source were mass identified as being solvated protons of general formula (H(2)O)(n)H(+) with (H(2)O)(2)H(+) as the most abundant reactant ion. The negative reactant ions produced were mass identified primarily as CO(3)(-), NO(3)(-), NO(2)(-), O(3)(-) and O(2)(-) of various relative intensities. The predominant ion and relative ion ratios varied depending upon source construction and supporting gas flow rates. A few compounds including drugs, explosives and amines were selected to evaluate the new ionization source. The source was operated continuously for 3 months and although surface deterioration was observed visually, the source continued to produce ions at a rate similar that of the initial conditions.
最近开发的一种大气压电离源——分布式等离子体电离源（DPIS），通过质谱（MS）和离子迁移谱（IMS）对其进行了表征，并与常用的大气压电离源进行了比较。该源由两个不同尺寸的电极组成，中间隔着一层薄电介质。在电极上施加高射频电压会在空气中产生等离子体，从而产生正离子和负离子。这些反应离子随后使分析物蒸气离子化。产生的反应离子与传统点对面电晕放电离子源中产生的离子相似。该源产生的正反应离子经质量鉴定为通式为（H₂O）ₙH⁺的溶剂化质子，其中（H₂O）₂H⁺是最丰富的反应离子。产生的负反应离子经质量鉴定主要为具有不同相对强度的CO₃⁻、NO₃⁻、NO₂⁻、O₃⁻和O₂⁻。主要离子和相对离子比率因源结构和辅助气体流速而异。选择了包括药物、爆炸物和胺类在内的几种化合物来评估这种新的电离源。该源连续运行了3个月，尽管从视觉上观察到表面有劣化现象，但该源仍以与初始条件相似的速率继续产生离子。
