Development of amyloid β (1-42) certified reference material NMIJ CRM 6210-a.

Amyloid β is a well-known peptide biomarker for Alzheimer's disease. Various methods for amyloid β such as immunological assays have been reported. It is important to establish metrological traceability using a certified reference material (CRM) at the highest level in the calibration hierarchy to assess equivalence of measured values obtained from each method. Herein, we developed a CRM for amyloid β, named as NMIJ CRM 6210-a, with a concentration traceable to the International System of Units (SI). This CRM comprises a lyophilized synthetic peptide with a human amyloid β (1-42) sequence (hereafter, amyloid β) and includes oxidated, deamidated, and isomerized forms of amyloid β. Two certified values were assigned for the mass concentration of total amyloid β (a mixture of amyloid β and its oxidized, deamidated, and isomerized forms) and amyloid β, determined via amino acid analyses with two different hydrolysis methods with different liquid chromatography mass spectrometry methods coupled to isotope-dilution mass spectrometry on the reconstituted solution of the candidate material with (1.00