Method Development
Low pressure plasma ion sources for atomic and molecular mass spectrometry
For a number of years we, in this laboratory and partly in collaboration with others, have developed a low pressure inductively coupled plasma (LP-ICP) as an ion source for mass spectrometry which is capable of providing information about both the elemental composition and molecular structure of the analyte. Evans et al. have operated a low pressure helium inductively coupled plasma as an ion source in two modes, namely ‘atomic’ and ‘molecular’, thereby obtaining atomic and molecular mass spectra respectively with one instrument. Hence, unknown compounds can be identified in ‘molecular’ mode, and quantified, using similar but not necessarily identical compounds, in ‘atomic’ mode. Other tuneable sources used for mass spectrometry, such as corona discharges, ionspray and electrospray, do not produce unequivocally elemental mass spectra, and are bedevilled by recombination reactions which result in cluster ions. In contrast, the LP-ICP can be operated over a wide range of power and pressure, thereby allowing a choice of conditions which either partially fragment or completely atomise the analyte.
The technology can be applied to a wide variety of applications where it is essential to know the molecular and atomic speciation of organo-metallic compounds such as: organo-platinum anti-cancer drugs and metabolites; metalloporphyrins and metallocorrin (e.g. vitamin B12), and metabolites; organo-metallic compounds in industrial by-products and waste streams (e.g. silicone manufacture, agrochemicals); copper and tin based organo-metallic compounds used in marine anti-fouling paints, and speciation of selenium, arsenic, mercury and lead compounds in the environment (e.g. contaminated land and shellfish); organo-metallic intermediates in organic reaction pathways, particularly with respect to reactions catalysed by organo-metallic compounds.
Publications
Barriada, J. L., Tappin, A. D., Evans, E. H. and Achterberg, E. P. (2007). Dissolved silver measurements in seawater. Trends in Analytical Chemistry 26, 809-817.
Kara, D., Fisher, A. and Hill, S.J. (2005).Preconcentration and determination of trace elements with 2,6-diacetylpyridine functionalized Amberlite XAD-4 by flow injection and atomic spectroscopy. Analyst 130, 1518-1523.
Kara, D., Fisher, A. and Hill, S.J. (2006). Comparison of some newly synthesised chemically modified Amberlite XAD-4 resins for the preconcentration and determination of trace elements by flow injection inductively coupled plasma-mass spectrometry (ICP-MS). Analyst 131, 1232-1240.
Marcus, R.K., Evans, E.H. and Caruso, J.A. (2005). Tunable plasma sources in analytical spectroscopy: Current status and projections. Journal of Analytical Atomic Spectrometry 15, 1-5
Nash, M.J., Maskall, J.E. and Hill, S.J. (2006). Developments with anion exchange stationary phases for HPLC-ICP-MS analysis of antimony species. Analyst 131, 724-730.
O'Connor, G., Rowland, S.J. and Evans, E.H. (2002). Evaluation of gas chromatography coupled with low pressure plasma source mass spectrometry for the screening of volatile organic compounds in food. Journal of Separation Science 25, 839-846
Pazos-Capeans, P., Barciela-Alonso, M.C., Bermejo-Berrera, A., Bermejo-Berrera, P., Fisher, A. and Hill, S.J. (2006). On-line sequential determination of Cr(III) and Cr(VI) with selective elution of solid extracts using an alumina column. Atomic Spectroscopy 27, 107 -116.
Santamaria-Fernandez, R., Cave, M.R. and Hill, S.J. (2006). Trace metal distributions in the Arosa estuary (NW Spain): The application of a recently developed sequential extraction procedure for metal partitioning. Analytica Chimica Acta 557, 344-352.