Many scientific endeavors are dependent upon accurate quantification of medicine and endogenous substances in biological samples; the main target of bioanalysis within the pharmaceutical industry is to supply a quantitative measure of the active drug and/or its metabolite(s) for the aim of pharmacokinetics, toxicokinetics, bioequivalence and exposure–response (pharmacokinetics/pharmacodynamics studies). Bioanalysis also applies to drugs used for illicit purposes, forensic investigations, anti-doping testing in sports, and environmental concerns. Bioanalysis was traditionally thought of in terms of measuring small molecule drugs. However, the past twenty years has seen a rise in biopharmaceuticals (e.g. proteins and peptides), which are developed to deal with many of an equivalent diseases as small molecules. These larger biomolecules have presented their own unique challenges to quantification. the primary studies measuring drugs in biological fluids were administered to work out possible overdosing as a part of the new science of forensic medicine/toxicology. Initially, nonspecific assays were applied to measuring drugs in biological fluids. These were unable to discriminate between the drug and its metabolites; for instance , aspirin (circa 1900) and sulfonamides (developed within the 1930s) were quantified by the utilization of colorimetric assays. Antibiotics were quantified by their ability to inhibit bacterial growth. The 1930s also saw the increase of pharmacokinetics, and intrinsically the will for more specific assays.[2] Modern drugs are stronger , which has required more sensitive bioanalytical assays to accurately and reliably determine these drugs at lower concentrations. This has driven improvements in technology and analytical methods.