Amino Acid Analysis (AAA) by RP-HPLC is used in protein characterization to analyse peptide or protein concentration, content and molar ratio or, alongside UV spectrophotometry, to gain an extinction coefficient. This analysis is used throughout all stages of drug discovery, or to demonstrate comparability and consistency between batches for release during the manufacturing phase. Amino acid analysis is a necessary part of protein characterisation and can also be used for estimation of extinction coefficient, total amino acids including cysteine, tryptophan, hydroxyproline & free amino acids, including asparagine & glutamine. By determination of extinction coefficient the method is validated for the product and includes molecular weight measurement by MALDI-TOF MS. The validated method may be used for batch release. Protein concentration may be calculated by relating extinction coefficient to Optical Density measurement, which is performed using a UV spectrometer at 280nm. Amino acid analysis is a key part of the ICH Q6B guidelines for characterisation and confirmation of biopharmaceuticals in support of new marketing applications.

In chemistry, an amino acid is a molecule that contains both amine and carboxyl functional groups. In biochemistry, this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent.[1] In the alpha amino acids, the amino and carboxylate groups are attached to the same carbon, which is called the ?-carbon. . Amino acids combine in a condensation reaction that releases water and the new 'amino acid residue' that is held together by a peptide bond. Proteins are defined by their unique sequence of amino acid residues; this sequence is the primary structure of the protein. Twenty standard amino acids are used by cells in protein biosynthesis, and these are specified by the general genetic code. These 20 amino acids are biosynthesized from other molecules, but organisms differ in which ones they can synthesize and which ones must be provided in their diet. The ones that cannot be synthesized by an organism are called essential amino acidschemical industries as well as agriculture and environmental engineering