Profiling pH Changes in the Electrospray Plume

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• 作者：Shaolian Zhou ; Benjamin S. Prebyl ; and Kelsey D. Cook
• 刊名：Analytical Chemistry
• 出版年：2002
• 出版时间：October 1, 2002
• 年：2002
• 卷：74
• 期：19
• 页码：4885 - 4888
• 全文大小：58K
• 年卷期：v.74,no.19(October 1, 2002)
• ISSN：1520-6882

文摘

Laser-induced fluorescence spectrometry is used to profile pH changes as droplets evaporate in an electrosprayplume by measuring emission spectra of 2(or 4)-[10-(dimethylamino)-3-oxo-3H-benzo[c]xanthene-7-yl]-benzenedicarboxylic acid (carboxy SNARF-1), a pH-sensitivefluorescent dye. The observed pH changes depend oninitial droplet pH and polarity. In some instances, smallor negligible changes of pH are observed, consistent withexpected buffering. The pH of initially acidic dropletsdecreases along the spray axis in both positive andnegative ion modes, to an extent larger than expected fromsolvent evaporation. This phenomenon may be a manifestation of droplet cooling, droplet subdivision, or heterogeneous charge distribution within the spray plume orwithin individual ES droplets.