Abstract
The field of ambient ionisation within the mass spectrometry community has been growing
since the early 2000s. Currently, very little research has been conducted into if one technique
could be recommended for use over another. This is because the literature contains examples
where several different analytes and mass spectrometers have been used, making
conclusions difficult to draw. The aim of the research presented in this thesis was to study a
number of ambient ionisation techniques using a consistent set of analytes on the same mass
spectrometer.
A set of analytes, (illicit drugs, amino acids, and explosives) were chosen based on their
functional groups, varying masses and ability to ionise in positive or negative mode. These
analytes are of interest for screening of drugs of abuse, security, and clinical settings.
Ambient ionisation techniques investigated included atmospheric solids analysis probe,
thermal desorption corona discharge, direct analysis in real time, secondary electrospray
ionisation and paper spray, all of which were coupled to a waters QDa single quadrupole
mass spectrometer. A number of these techniques were also compared to electrospray
ionisation, which was used to demonstrate the capability of the mass spectrometer itself. The
selectivity, sensitivity (in terms of the limit of detection), repeatability and linearity were
investigated.
The results have shown that the choice of ambient ionisation technique can have an impact
on the selectivity and sensitivity of the data collected. Ambient ionisation mass spectrometry
is best suited for targeted screening applications, where the sample is unlikely to be the
limiting factor, however reasonable limits of detection can be achieved with a number of
these techniques. A linear relationship can be established at various concentration levels
depending on the analyte tested, indicating the possibility of use for semi-quantitative
analysis.
The experimental design/setup has implications on both sensitivity and selectivity of the
results produced. Based on the results, an overall top performer was not identified, however,
recommendations surrounding suitability for applications could be suggested.