Development of a certified reference material of human serum albumin: certification and value assignment via amino acid analyses

摘要

Serum albumin is widely used as the standard material for various protein quantifications. Some commonly used methods to quantify albumin include the bromocresol green and bromocresol purple methods that use bovine serum albumin as a calibrant. To achieve the exact matching of the analyte and calibrant in human serum measurements, human serum albumin (HSA) is the ideal calibrant because it minimizes the measurement bias due to structural difference. Herein we describe the development of a certified reference material (CRM) for the HSA solution, namely NMIJ CRM 6202-a, with SI traceability at the National Metrology Institute of Japan (NMIJ). The certification process involved preparation of the material, homogeneity studies, stability studies, and value-assignment. The certified concentration of the candidate CRM was determined via amino acid analyses using isotope-dilution mass spectrometry with amino acid CRMs as the calibrants. The amino acid analyses were performed using microwave-assisted liquid phase and gas phase hydrolyses with hydrochloric acid under the optimized conditions, followed by measurements using liquid chromatography-mass spectrometry after a pre-column derivatization of the hydrolyzed amino acids. The certified value of this CRM was determined to be (74.3 +/- 2.1) g L-1; the number following +/- represents the expanded uncertainty (k=2).