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首页> 外文期刊>Journal of mass spectrometry: JMS >Further studies on the signal enhancement effect in laser diode thermal desorption-triple quadrupole mass spectrometry using microwell surface coatings
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Further studies on the signal enhancement effect in laser diode thermal desorption-triple quadrupole mass spectrometry using microwell surface coatings

机译：进一步研究Microwell表面涂层激光二极管热解吸 - 三重四极杆质谱法的信号增强效果

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The laser diode thermal desorption (LDTD) ionization source allows ultrafast and sensitive analysis of small molecules by mass spectrometry. Signal enhancement in LDTD has been observed when coating the surface of sample microwells with a solution of ethylenediaminetetraacetic acid (EDTA) or nitrilotriacetic acid. Here we present a quantitative analysis of signal enhancement using solutions of diverse commercial proteins (lysozyme, immunoglobulin G, albumin, and fibrinogen) as coatings. Results showed that compounds with polar chemical functions such as carboxylic acid, sulfonyl, and nitro had signal enhancement factors, in most cases higher than 10, when using any of the tested proteins as coating agent. Analysis of variance revealed that immunoglobulin G and fibrinogen gave the best results. However, the signal enhancement factors obtained with these proteins were not superior to those observed with EDTA. To explain the signal enhancement effect of proteins, analysis by scanning electron microscopy of dried samples on the microwell sample plates was carried out. Images showed that salicylic acid, one of the compounds with the highest observed signal enhancement, formed a thick layer when applied directly on the uncoated surface, but it formed small crystals (<1 mu m) in the presence of protein or EDTA coatings. Further crystallographic studies using powder X-ray diffraction showed that the crystalline form of salicylic acid is modified in the presence of EDTA. Salicylic acid when mixed with EDTA had a higher percentage of amorphous phase (38.1%) than without EDTA (23.1%). These results appear to confirm that the diminution of crystal size of analytes and the increase of amorphous phase are implicated in signal enhancement effect observed in LDTD using microwell surface coatings. To design better coatings and completely elucidate the signal enhancement effect in LDTD, more studies are necessary to understand the effects of coatings on the ionization of analytes.
机译：激光二极管热解吸（LDTD）电离源允许通过质谱法超速和敏感的小分子分析。当用乙二胺四乙酸（EDTA）或氮酰基乙酸溶液涂覆样品微孔的表面时，已经观察到LDTD中的信号增强。在这里，我们使用各种商业蛋白质（溶菌酶，免疫球蛋白G，白蛋白和纤维蛋白原）作为涂层的信号增强的定量分析。结果表明，当使用任何测试的蛋白质作为涂布剂时，大多数情况下，具有信号增强因子，羧酸，磺酰基和硝基等极性化学官能的化合物具有信号增强因子。方差分析显示免疫球蛋白G和纤维蛋白原给出了最佳结果。然而，用这些蛋白质获得的信号增强因子不优于用EDTA观察到的因子。为了解释蛋白质的信号增强效果，进行了通过在微孔样品板上扫描干燥样品的电子显微镜的分析。图像显示，当直接在未涂覆的表面上施加时，在具有最高观察到的信号增强的化合物之一，形成厚层，但在蛋白质或EDTA涂层存在下形成小晶体（<1μm）。使用粉末X射线衍射的进一步结晶研究表明，在EDTA存在下修饰了水杨酸的结晶形式。与EDTA混合时的水杨酸具有比没有EDTA的无定形相（38.1％）的更高百分比（38.1％）。这些结果似乎证实分析物的晶体尺寸的减少和非晶相的增加涉及使用微孔表面涂层在LDTD中观察到的信号增强效果。为了设计更好的涂料并完全阐明LDTD中的信号增强效果，更多的研究是了解涂层对分析物电离的影响。

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