Certification of NIST standard reference material 2389a, amino acids in 0.1 mol/L HCl—quantification by ID LC-MS/MS
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An isotope-dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS) measurement procedure was developed to accurately quantify amino acid concentrations in National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2389a—amino acids in 0.1 mol/L hydrochloric acid. Seventeen amino acids were quantified using selected reaction monitoring on a triple quadrupole mass spectrometer. LC-MS/MS results were compared to gravimetric measurements from the preparation of SRM 2389a—a reference material developed at NIST and intended for use in intra-laboratory calibrations and quality control. Quantitative mass spectrometry results and gravimetric values were statistically combined into NIST-certified mass fraction values with associated uncertainty estimates. Coefficients of variation (CV) for the repeatability of the LC-MS/MS measurements among amino acids ranged from 0.33% to 2.7% with an average CV of 1.2%. Average relative expanded uncertainty of the certified values including Types A and B uncertainties was 3.5%. Mean accuracy of the LC-MS/MS measurements with gravimetric preparation values agreed to within |1.1|% for all amino acids. NIST SRM 2389a will be available for characterization of routine methods for amino acid analysis and serves as a standard for higher-order measurement traceability. This is the first time an ID LC-MS/MS methodology has been applied for quantifying amino acids in a NIST SRM material.
KeywordsAmino acids Standard reference material Mass spectrometry Isotope dilution LC-MS/MS
The authors would like to thank Brandi Benford and Brian Lang (NIST) for their help in validating purity measurements for unlabeled amino acid powders.
Certain commercial equipment, instruments, or materials are identified in this paper to specify adequately the experimental procedure. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.
- 8.KC Taylor BN. NIST Technical Note 1297. 1994Google Scholar
- 9.International Organization for Standardization. ISO (1993) Guide to the expression of uncertainty in measurement. 1993. Geneva, SwitzerlandGoogle Scholar
- 10.Meyer VR (1995) Error sources in the determination of chromatographic peak size ratios. Marcel Dekker, New YorkGoogle Scholar
- 11.Levenson MS, Banks DL, Eberhardt KR, Gill LM, Guthrie WF, Liu HK, Vangel MG, Yen JH, Zhang NF (2000) J Res Natl Inst Stand Technol 105:571–579Google Scholar