Surface-activated no-discharge atmospheric pressure chemical ionization

A new ionization method named surface‐activated chemical ionization (SACI) has been realized. In this invention a commercially available atmospheric pressure chemical ionization (APCI) chamber, employed without any corona discharge (no‐discharge APCI), has been modified with the insertion of a gold surface, leading to a significant improvement in the ionization efficiency. The ionization of the sample takes place by both gas‐phase and surface‐activated processes. This new ionization source is able to generate ions with high molecular mass and low charge states, leading to improved sensitivity and reduced noise. The new device has been tested in the analysis of some peptides. A comparison between the performance with and without the presence of the surface, and the optimization of the operating conditions (nebulizing gas flow, sample solution flow, pH of solution, and surface area), are reported and discussed. Copyright © 2003 John Wiley & Sons, Ltd.