Arsenic exists as many different chemical forms including inorganic, methylated and dietary species. The toxicity of these species varies: some are highly toxic and can cause adverse health effects in many parts of the body; others are considered relatively non-toxic. Monitoring arsenic exposure is usually accomplished by its direct measurement in biological fluids. Urine is the specimen of choice for assessing arsenic exposure, because of its short biological half-life in blood. There have been very few studies of arsenic species in blood, yet such research can provide valuable information on arsenic distribution and its metabolism in the body.

The principal aim of this thesis was to conduct a thorough evaluation of current analytical methods for the determination of (a) total arsenic in whole blood and urine and (b) five arsenic species in blood and urine. A method for measuring total arsenic in urine was developed based on coupling an on-line oxidation system to hydride generation atomic fluorescence spectrometry. The method for total arsenic was optimized to include up to seven arsenic species that may be present in urine including those of dietary origin.

For speciation analysis, a method was developed to quantify up to five arsenic species separately in either a blood or urine matrix, thus providing a more complete picture of arsenic exposure and metabolism. The method incorporated ion-pair liquid chromatography coupled to inductively coupled plasma mass spectrometry. The methods were validated with various reference materials, including a new Standard Reference Material^® 2669 Arsenic Species in Frozen Human Urine.

The validated method was used to investigate (a) the uptake and distribution of arsenic species in blood following consumption of a meal containing seaweed and mushrooms, and (b) arsenic speciation in matching pairs of archived blood and urine specimens from a biomonitoring study. Results show that most arsenic in blood is present as arsenobetaine. A small interlaboratory study of arsenic speciation in whole blood was conducted that included four laboratory participants specializing in these measurements. Overall interlaboratory agreement was judged reasonable given the lack of standard protocols and certified reference materials for this analysis.