Analytical toxicology is the use of the entire range of qualitative and quantitative chemical, immunochemical, and physical techniques used in sample preparation, separation, assay calibration, detection and identification, and quantification for the purposes of toxicological research and testing. Examples of the objectives of such analysis include determining the levels of exposure to potential toxicants via air, water, or food; verifying exposure levels to doses for animals in experimental studies; determining levels of xenobiotics and their metabolites in animal studies; and screening blood and urine for the presence of illicit drugs or their metabolites. The diagnosis and treatment of health problems induced by chemical substances and the closely allied field of therapeutic drug monitoring rely on analytic toxicology. Advances in analytic toxicology have added both power and problems to toxicology, with the increases in sensitivity and specificity.