Methods of temperature measurement by mass spectrometry have been critically
reviewed. It was concluded that the most appropriate method depended critically on the
availability of fundamental data, hence a database of fundamental spectroscopic
constants, for diatomic ions which cause interferences in ICP-MS, was compiled. The
equilibration temperature, calculated using the different methods and using various
diatomic ions as the thermometric probes, was between c.a. 400 - 10,000 K in the
central channel, and between c.a. 600 - 16,000 K when the plasma was moved 1.8 mm
off-centre. The wide range in temperature reflected the range of temperature
measurement methods and uncertainty in the fundamental data.
Optical studies using a fibre optic connected to a monochromator were performed in
order to investigate the presence of interferences both in the plasma and the interface
region of the ICP-MS, and the influence of a shielded torch on these interferences. It was
possible to determine the presence of some species in the plasma, such as the strongly
bound metal oxides, however, no species other than OH were detected in the interface
region of the ICP-MS. The OH rotational temperature within the interface region of the
ICP-MS was calculated to be between 2,000 - 4,000 K.
The effect of sampling depth, operating power, radial position and solvent loading, with
and without the shielded torch, on the dissociation temperature of a variety of
polyatomic interferences was investigated. These calculated temperatures were then used
to elucidate the site of formation for different polyatomic interferences. Results
confirmed that strongly bound ions such as MO+ were formed in the plasma, whereas
weakly bound ions such as ArO+ were formed in the interface region due to gross
deviation of the calculated temperatures from those expected for a system in thermal
equilibrium.
Date of Award | 2000 |
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Original language | English |
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Awarding Institution | |
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FUNDAMENTAL STUDIES OF INTERFERENCES IN ICP - MS
ROWLEY, L. K. (Author). 2000
Student thesis: PhD