ソニックスプレーイオン化法とイオン生成過程

概要

論文の詳細を見る
Sonic spray ionization technique has been developed as an interface in LC/MS and CE/MS. In this technique, a solution from a capillary is sprayed with a sonic gas flow coaxial to the capillary, and gas-phase ions and charged droplets are formed under atmospheric pressure. The amount of the produced ions depends on the gas velocity and has a maximum at the sonic velocity. The origin of the charged species cannot be ascribed to the traditional models of friction electrification, electrical double layer formed near the capillary surface, or statistical charging. An explanation is proposed based on nonuniformity of positive and negative ion concentrations near the solution surface caused by the surface potential. Based on the explanation, we have modified our technique to regulate the nonuniformity by applying an external electric field to the solution surface. Then, the ion amount is found to be dramatically enhanced and multiply-charged ions are readily formed. The analysis of the droplets produced from a nonvolatile solution also shows that the abundance of the droplets having charge numbers close to the Layleigh limit increases as the external electric field increases. These results suggest that ions are readily formed from solutions having a very wide range of chemical properties and flow rates, since highly-charged droplets are produced from the solutions by the shear stress due to the sonic gas flow.
1999-10-01