A flow injection hydride generation atomic absorption (AAS) method has been developed for the analysis of arsenic species. The technique has been optimised for the analysis of arsenite, arsenate, monomethylarsonate(MMA) and dimethylarsinate(DMA) with detection limits of 9, 35, 24 and 24 ppb respectively being achieved. The method described offers the advantage of the reproducible use of small volumes and the ability to achieve rapid sample throughput. The optimised hydride generation AAS method was then investigated as a detector for HPLC. The resulting hyphenated technique allows the separation and detection of the individual arsenic species at ppm levels. As lower detection limits are required for the analysis of arsenic species in real samples an on-line preconcentration technique has been developed, resulting in improved detection limits and the removal of matrix interferences. Finally a matrix solid phase dispersion technique was developed for the extraction of arsenic species from fish which did not result in the loss of information on speciation. A sensitive and reliable method was developed for the determination of aflatoxins Bj, B2, Gj, and G2, ochratoxin A and zearalenone in animal feed ingredients. A multi-toxin extraction and clean-up procedure was used, with dichloromethane: 1 M hydrochloric acid (10:1) being used for the extraction and gel permeation chromatography being used for the clean-up. The liquid chromatographic method developed for the separation of the six mycotoxins involved gradient elution with reverse-phase Cjg column and fluorescence detection. Recoveries, repeatability and reproducibility have been determined on maize, palm and wheat. The detection limits varied depending on the type of feed.