Trace metal determinations in aqueous environments

The accurate determination of metal ions at trace levels in environmental matrices is a complex problem and as a result, methods for determination and preconcentration of trace metals are continuously under investigation. In this thesis a number of approaches for metal determination and preconcentration are described. Chapter 1 looks at trace metal speciation methods. Traditional and novel methods of metal determination and preconcentration are described including their advantages and disadvantages. Chapters 2 and 3 describe the use of column-switching techniques for preconcentration of Cr(VI) and Cr(III) respectively. An ion-exchange chromatographic technique with post column derivitization detection is described for determination of hexavalent chromium, while a reversed-phase chromatographic technique, using complexation with 8-hydroxyquinoline, is reported for the trivalent species. The use of dye-coated stationary phases for determination of Cr(VI) anion is described in chapter 4 in which exhausted reversed-phase HPLC columns are utilized to support methylene blue and crystal violet dyestuffs. Determination of metal ions by capillary electrophoresis (CE) using oncolumn complexation with 4,2-pyridylazo resorcinol (PAR) followed by peak stacking is described in chapters 5 and 6. This method of trace enrichment achieved a limit of detection of 1.10‘8 M for Co(II), Zn(II) and Fe(II). For Pb(II) determination, described in chapter 6, a 100 fold improvement in sensitivity was achieved using on-column complexation as opposed to precolumn derivitization. Speciation o f Cr(III) and Cr(VI) using two separation techniques is reported in chapter 7. Comparison of an ion-exchange chromatographic technique using post column derivitization detection, and a capillary electrophoretic separation technique is described. Both of these procedures allowed simultaneous determination o f the two chromium species