Wortmann Arno, Kistler-Momotova Anna, Zenobi Renato, Heine Martin C, Wilhelm Oliver, Pratsinis Sotiris E
Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland.
J Am Soc Mass Spectrom. 2007 Mar;18(3):385-93. doi: 10.1016/j.jasms.2006.10.010. Epub 2006 Nov 16.
We investigated how chemical equilibria are affected by the electrospray process, using simultaneous in situ measurements by laser-induced fluorescence (LIF) and phase Doppler anemometry (PDA). The motivation for this study was the increasing number of publications in which electrospray ionization mass spectrometry is used for binding constant determination. The PDA was used to monitor droplet size and velocity, whereas LIF was used to monitor fluorescent analytes within the electrospray droplets. Using acetonitrile as solvent, we found an average initial droplet diameter of 10 microm in the electrospray. The PDA allowed us to follow the evolution of these droplets down to a size of 1 microm. Rhodamine B-sulfonylchloride was used as a fluorescent analyte within the electrospray. By spatially resolved LIF it was possible to probe the dimerization equilibrium of this dye. Measurements at different spray positions showed no influence of the decreasing droplet size on the monomer-dimer equilibrium. However, with the fluorescent dye pair DCM and oxazine 1 it was shown that a concentration increase does occur within electrosprayed droplets, using fluorescence resonance energy transfer as a probe for the average pair distance.
我们使用激光诱导荧光（LIF）和相位多普勒风速仪（PDA）进行同步原位测量，研究了电喷雾过程如何影响化学平衡。开展这项研究的动机在于，越来越多的出版物使用电喷雾电离质谱法来测定结合常数。PDA用于监测液滴大小和速度，而LIF用于监测电喷雾液滴内的荧光分析物。使用乙腈作为溶剂，我们发现电喷雾中初始液滴的平均直径为10微米。PDA使我们能够追踪这些液滴直至其尺寸减小到1微米。罗丹明B - 磺酰氯被用作电喷雾内的荧光分析物。通过空间分辨LIF能够探测该染料的二聚平衡。在不同喷雾位置进行的测量表明，液滴尺寸减小对单体 - 二聚体平衡没有影响。然而，对于荧光染料对二氯甲烷和恶嗪1，使用荧光共振能量转移作为平均对距离的探针表明，在电喷雾液滴内确实发生了浓度增加。
