Trace metal speciation studies

Abstract

The development of methods capable of determining individual metal species at trace levels is a widely researched topic. The majority of the techniques developed for this purpose involve the use of “coupled” instrumental techniques to separate and detect metal species at low concentrations, also additional derivatisation steps are often required prior to detection. This approach requires lengthy analysis times and high manual input to construct and maintain the interface between the two instruments. Complicated sample preparation procedures are also necessary for tissue samples. These factors discourage the implementation of routine environmental monitoring of trace metal species. In the course of this study, alternative techniques for trace metal speciation are examined. The criteria for these techniques is that each should be straightforward in design and operation requiring a minimal level of manual input while remaining cost effective. The use of a solid phase extraction technique known as Matrix Solid Phase Dispersion (MSPD) is evaluated for extracting arsenic species from fish tissues. MSPD involves physically grinding up tissue samples with a quantity of chromatographic packing material and packing the resulting mixture into a column followed by selective elution of the analytes with mobile phase. The technique is developed and validated for five arsenic species. The effectiveness of this technique is then assessed by comparison with an existing liquid-liquid extraction protocol. The feasibility of capillary electrophoretic methods (CE) for routine trace metal speciation is examined for arsenic and methylated tin species respectively. This technique involves the separation of charged species in narrow bore capillary tubing under the influence of an electric field. CE offers the benefits of highly efficient separations, short analysis times, minimal sample preparation requirements and small reagent consumption. Problems with low sensitivity can be overcome with electrostacking and indirect detection methods which allows the technique to be extended to the area of trace metal analysis