Association Constant - A response between antibody and its determinant which comprises a measure of affinity. Immunoassay - A qualitative or quantitative assay technique based on the measure of interaction of high affinity antibody with antigen used to identify and quantify proteins. High Performance Liquid Chromatography (HPLC) - An instrumental separation method used to characterize or to find out the purity of a BDP by passing the product (or its element peptides or certified amino acids supplier acids) in liquid type over a chromatographic column containing a strong help matrix.