This chapter provides guidance and procedures used for characterization of biotechnology-derived articles by amino acid analysis. This chapter is harmonized with the corresponding chapter in JP and EP. Portions of the chapter that are not harmonized with the other two pharmacopeias are marked by the symbol ⧫. The footnote below is in the USP but is not in the EP or JP. Other characterization tests, also harmonized, are shown in Capillary Electrophoresis 〈1053〉 , Biotechnology-Derived Articles—Isoelectric Focusing 〈1054〉 , Biotechnology-Derived Articles—Peptide Mapping 〈1055〉 , Biotechnology-Derived Articles—Polyacrylamide Gel Electrophoresis 〈1056〉 , and Biotechnology-Derived Articles—Total Protein Assay 〈1057〉 .