Development of a Liquid Beam Technique for Characterization of Solute Molecules in Solution.

发展了对溶液中溶质分子的高灵敏度检测和表征。该技术由连续液流(液束)和多光子电离质谱仪组成。为了检验这项技术的性能，测试了几种溶解在甲醇、乙醇和水中的芳香族分子。液束是通过20微米的孔径将溶液注入真空室来制备的。当束被注入时，腔室的压力能够维持在10^&lt；-5；-10^&lt；-6 Torr。一束波长约为270 nm的激光被允许穿过液体光束，产生的光离子由于库仑爆炸而被喷射到真空中。通过对光离子的脉冲加速，获得了约300的质量分辨率，得到了多种结果：例如，在苯胺-乙醇溶液的光致电离中，苯胺溶质分子在溶液中通过共振双光子过程电离，并通过库仑爆炸被喷射出液束。此外，苯胺分子倾向于随着苯胺浓度的增加而增加。在表面活性剂溶液的情况下，例如N-十二烷基吡啶的水溶液，观察到从表面活性剂的碳氢链断裂的碳氢化合物。这一结果表明，表面活性剂被放置在液体表面，其碳氢链在外面。为了最大限度地提高灵敏度，将开发一种从液态束中驱逐光离子的方法。

High sensitive detection and characterization of solute molecules in solutions were developed. This technique consists of a continuous liquid flow (liquid beam) and multiphoton ionization mass spectrometry. Several aromatic molecules dissolved in methanol, ethanol and water were tested in order to examine the performance of this technique.The liquid beam was prepared by injecting a solution into a vacuum chamber through a 20 mum aperture. The pressure at the chamber was able to be maintained at 10^<-5>-10^<-6> Torr when the beam was injected. A laser beam with a wave length of about 270 nm was allowed to cross the liquid beam, and the photoions produced in the beam were ejected into vacuum as a result of Coulomb explosion. The mass resolution was attained to be about 300 by using pulse acceleration of the photoions.A variety of results were obtained: In the photoionization of an aniline-ethanol solution, for example, the aniline solute molecule is ionized via a resonant two-photon process in the solution and is ejected out of the liquid beam by Coulomb explosion. In addition, the aniline molecules tend to be associated with increasing the aniline concentration. In the case of a surfactant solution, such as an aqueous solution of N-dodencyl pyridinium, hydrocarbons fragmented from the hydrocarbon chain of the surfactant were observed. This result indicates that the surfactant is placed on the liquid surface with its hydrocarbon chain outside. In order to maximize the sensitivity limit, a method of expelling the photoions from the liquid beam will be developed.