In particle induced desorption-ionization mass spectrometry the strength of an
analyte's signal under a given set of bombardment conditions is usually considered to
be representative of the analytes relative surface activity. This rationale is generally
used to explain differences in the technique's sensitivity between and within various
classes of compound. In liquid matrix assisted secondary ion mass spectrometry
(SIMS) sensitivity enhancement of ionic analytes by pairing with surface active
counterions has been demonstrated by several groups. This technique has been utilized
in this work to achieve a 10,000 fold enhancement in the signal for ATP on a double
focusing magnetic sector instrument and to detect femtomole quantities of nucleoside
monophosphates on a time-of-flight instrument. The analyte's signal, however, is
dependent on both the analyte bulk concentration and that of the surfactant.
Additionally, the surfactant concentration that produces the maximum analyte signal
changes with the analyte concentration. In this study, this phenomenon has been
modeled in terms of conventional solution equilibria and surface chemical principles.
It is assumed that the initial surface composition and the bulk concentration are the
boundary conditions of a steady state established by the competing processes of surface
sputtering and surface replenishment from the bulk during analysis. Calculated surface
excesses correlate well with observed relative ion intensities, suggesting that equilibrium
conditions are approached in the sample matrices despite the outwardly dynamic nature
of the sputtering processes. / Graduation date: 1994
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36760 |
| Date | 18 March 1993 |
| Creators | Pavlovich, James Gilbert |
| Contributors | Barofsky, Douglas F. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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