The role of different phenomena in surface-activated chemical ionization (SACI) performance
Articolo
Data di Pubblicazione:
2005
Citazione:
The role of different phenomena in surface-activated chemical ionization (SACI)
performance / S. Cristoni, L. Rossi Bernardi, F. Guidugli, M. Tubaro, P. Traldi, M. Tubaru, P. Traldi, F. Guidugli. - In: JOURNAL OF MASS SPECTROMETRY. - ISSN 1076-5174. - 40:12(2005 Dec), pp. 1550-1557. [10.1002/jms.913]
Abstract:
In previous studies, the production of ions in an APCI source without any corona
discharge was observed, and the intensity of the ion signals showed significant
increases on placing a metallic surface at 45 degrees inside an orthogonal ion
source. This method was named surface-activated chemical ionization (SACI). The
present study was performed to investigate the mechanisms of ion production with
or without the presence of the metallic surface, by varying instrumental
parameters and the geometrical configuration. Approximate calculations show
that, in the absence of corona discharge and of any additional surfaces, ions
cannot be produced by collisional phenomena, because of their low kinetic
energy, in the 10(-2) to 10(-3) eV range. Two alternative possibilities have
been considered: the first takes into account that ions may originate by
collision of neutral clusters of polar solvent molecules with the APCI source
surfaces through clusterelectric effect. The second takes into account that the
water dissociation constant k(w) is temperature dependent, passing from
10(-14.1669) at 20 degrees C to 10(-12.4318) at 90 degrees C. It means that the
[H(+)] varies from 8.3 x 10(-8) to 6.1 x 10(-7) M going from 20 to 90 degrees C.
Hence, at the high temperatures experimented in the APCI vaporizer, H(+) becomes
available in solution in molar quantities analogous to those of analyte, and the
protonation of the analyte itself can consequently occur. The activation of
further ionization processes in the presence of the metallic surface can be
reasonably attributed to interactions between gas-phase analyte molecules and
solvent molecules adsorbed on the surface. Experiments performed with a thin
layer of deuterated glycerol on the surface led to unequivocal results, i.e. the
production of [M + D](+) ions of the analyte
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
corona, APCI
Elenco autori:
S. Cristoni, L. Rossi Bernardi, F. Guidugli, M. Tubaro, P. Traldi, M. Tubaru, P. Traldi, F. Guidugli
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