The efficiency of desorption/ionization becomes more critical as the sampled surface area decreases. Desorption electrospray and desorption nanoelectrospray belong to ambient ionizations and enable direct surface analysis including mass spectrometric imaging. Lateral resolution in tens of micrometers was demonstrated for desorption nanoelectrospray previously, but sensitivity of the surface scan can be an issue. For desorption electrospray, the drag force in the source is driven by the flow of used gases and vacuum suction. Ion signal intensity can be improved by controlling the nebulizing gas flow rate or auxiliary pumping of a closed compartment in front of the mass spectrometer inlet. Because nanoelectrospray generates charged droplets without the assistance of a nebulizing gas, only vacuum suction drives the gas flow. In this study, the effect of pressure drop between the atmospheric and evacuated region of a mass spectrometer on the ion signal intensity was investigated for desorption nanoelectrospray. A modification of the commercial inlet was designed. An auxiliary pump was directly connected to an inner compartment of the modified mass spectrometer inlet through a needle valve that enabled the regulation of the reduced pressure. Adjustment of the pressure drop significantly increased signal intensity (more than one order of magnitude in some cases). To a lesser extent, the temperature of a heated capillary (an integral part of the inlet) also influenced the signal intensity. The applicability of desorption nanoelectrospray equipped with pressure regulation was demonstrated by the analysis of synthetic cathinones or a pill of paracetamol. Because pressure in the inlet depends on the diameters of orifices and the power of vacuum systems of mass spectrometers, the effect of the pressure regulation can be different for different instruments. Nevertheless, the presented results confirmed the importance of pressure drop‐driven transport for desorption nanoelectrospray efficiency and can encourage its new applications.

中文翻译：

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通过具有压力调节功能的定制入口增强解吸纳米电喷雾电离中的信号。

随着采样表面积的减小，解吸/电离的效率变得越来越关键。解吸电喷雾和解吸纳米电喷雾属于环境电离，可进行直接表面分析，包括质谱成像。先前已证明解吸纳米电喷雾的横向分辨率为数十微米，但是表面扫描的灵敏度可能是一个问题。对于解吸电喷雾，源中的阻力是由使用过的气体流和真空抽吸驱动的。可以通过控制雾化气体流速或在质谱仪入口前面的密闭隔室进行辅助泵送来改善离子信号强度。由于纳米电喷雾在没有雾化气体帮助的情况下产生带电液滴，因此只有真空抽吸才能驱动气流。在这个研究中，研究了用于解吸纳米电喷雾的质谱仪的大气和真空区域之间的压降对离子信号强度的影响。设计了商业进气口的改进。辅助泵通过针阀直接连接到改进型质谱仪入口的内部隔室，该针阀能够调节减压。压降的调节显着增加了信号强度（在某些情况下超过一个数量级）。在较小程度上，加热的毛细管（入口的组成部分）的温度也会影响信号强度。通过分析合成的卡西酮或扑热息痛丸，证明了具有压力调节功能的解吸纳米电喷雾的适用性。由于进样口中的压力取决于孔的直径和质谱仪真空系统的功率，因此对于不同的仪器，压力调节的效果可能会有所不同。然而，提出的结果证实了压降驱动传输对于解吸纳米电喷雾效率的重要性，并可以鼓励其新的应用。