Atomic Spectrometry Update. Clinical and biological materials, foods and beverages

Abstract

In our last Update we discussed in considerable depth the analytical developments for investigating functions and metabolism of elements in biological systems i.e. metallomics. This included methods for speciation and for surface analysis/visualization. The importance of this topic and the increase in research activity with the clinical and other areas is such that a new Atomic Spectrometry Update has been commissioned to review the current literature. This Update, with the title Elemental Speciation, will be published in the August edition of Journal of Analytical Atomic Spectrometry. We will continue to draw attention to important features particularly as they apply to the content of this Update without necessarily providing as much detail as in recent years. Several recent technical and instrumental developments were shown to be usefully applied to the analysis of biological specimens. An unusual device described as a multiple microflame quartz tube atomizer has been further improved and was used to detect As species by HG-FAAS. A system for AES, involving HPLC and a particle beam/hollow cathode, was used to separate and determine non-protein bound Fe and Fe-proteins. Output from the column went to an interface with a thermo-concentric nebulizer, heated spray chamber and a momentum separator, to remove eluent solvent vapours and produce a beam of dry particles which entered the hollow cathode glow discharge source for vaporization, excitation and emission. This maintains optimal chromatographic conditions without having to make compromises because of problems associated with solvent entering an ICP. A miniaturized AF spectrometer to determine hydride forming elements, described as a ‘lab-on-a-valve’, was used to measure As in hair and rice. The device consisted of a dielectric barrier discharge atomizer with an integrated arrangement for HG, gas-liquid separation, atomization and detection. With a 0.5 mL sample the LOD was 0.03 µg L⁻¹ for As. This portable instrument could revolutionise vapour generation analysis if its potential is fully realised. Methods for producing chemical vapours with Cu and Zn were demonstrated and applied to analysis of waters and biological RMs by AFS and AAS. Breath condensate was proposed as a new sample type applicable for monitoring occupational exposure to Cr while salivary As concentrations were shown to reflect drinking water levels. A useful study presented the changes in concentrations of metals in tissues stored in formalin for long periods of time. Elsewhere it was reported that, if samples are stored at very low temperatures prior to investigation for As species, then only metabolic intermediaries with As^V are found, suggesting that As^III analogues are artefacts. Nevertheless, methods for measuring As^III species continue to be reported, keeping this controversial issue open. Parallel work reveals yet more Se species in nature, especially in yeasts and plants. An increasing number of applications involving XRF were seen yet again during this review period. The writing team would welcome feedback from readers of this review and invite you to complete the Atomic Spectrometry Updates questionnaire at http://www.asureviews.org.