Surface‐activated no‐discharge atmospheric pressure chemical ionization

Abstract

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.

Surface‐activated chemical ionization versus electrospray ionization in the study of selected aluminium(III)/ligand solution equilibria

“…In recent years, other MS techniques have been developed which allow the detection of species directly from solution samples: APCI (atmospheric pressure chemical ionization), 2 APPI (atmospheric pressure photoionization), 3 SACI (surface-activated chemical ionization), 4 and APLI (atmospheric pressure laser ionization). 5 These techniques, and especially the most recently developed SACI and APLI, demonstrate improved sensitivity and reduced chemical noise with respect to ESI, 4,5 and they can be expected to be employed like ESI in the study of metal/ligand equilibria in solution.…”

Development and applications of surface‐activated chemical ionization

“…This could be the case for peptide ions, which depending on the solution pH, can be in an ionic form. In fact, in a previous investigation (Cristoni et al, 2003b) on SACI performances, a relationship between the…”

“…Most probably this is because the presence of low electric fields in the ionization chamber and consequently the chemical noise do not extracharge the solvent and therefore the cluster changed molecules and to their reactivity, strongly decrease. This ionization technique has been recently upgraded by Cristoni et al (Cristoni et al, 2003b) to the SACI ionization source that strongly increases the performance mainly in terms of sensitivity when compared to ESI, APCI, and ND-APCI.…”

Surface‐activated chemical ionization ion trap mass spectrometry in the analysis of 21‐deoxycortisol in blood

“…Recently, a new high sensitivity ionization technique named surfaceactivated chemical ionization (SACI) has been described. 18 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 leading to a high instrumental selectivity and sensitivity.…”

“…We postulate that the positively charged surface gives rise to the adsorption and orientation of compounds exhibiting a permanent dipole moment (e.g., H 2 O or CH 3 OH employed in the present LC/MS experiments), thus making protons more available for capture by the analyte neutral molecules and thus increasing the ionization efficiency. 18 Moreover, the application of a low surface potential makes it possible to obtain a better focusing of the ions into the mass analyzer. In the case of 21-DF, the applications of 150 V surface potential gives rise to a 500% increase in signal intensity with respect to that achieved without applying a potential to the floating surface.…”