Assay techniques are methods used to determine the presence, amount, or activity of a substance, often in a biological or chemical sample. These techniques are essential in fields like pharmacology, environmental science, and clinical diagnostics. Common types of assays include enzyme-linked immunosorbent assays (ELISA), spectrophotometry, and chromatography, each serving specific purposes based on the nature of the sample and the analyte of interest. The choice of assay technique depends on factors such as sensitivity, specificity, and the type of sample being analyzed. For instance, bioassays are used to measure the effects of substances on living organisms, while chemical assays focus on quantifying chemical compounds. Understanding these techniques is crucial for accurate data interpretation and decision-making in research and industry.