title: Development of isotope dilution-liquid chromatography/mass spectrometry combined with standard addition techniques for the accurate determination of tocopherols in infant formula.
abstract: During the development of isotope dilution-liquid chromatography/mass spectrometry (ID-LC/MS) for tocopherol analysis in infant formula, biased measurement results were observed when deuterium-labeled tocopherols were used as internal standards. It turned out that the biases came from intermolecular H/D exchange and intramolecular H/D scrambling of internal standards in sample preparation processes. Degrees of H/D exchange and scrambling showed considerable dependence on sample matrix. Standard addition-isotope dilution mass spectrometry (SA-IDMS) based on LC/MS was developed in this study to overcome the shortcomings of using deuterium-labeled internal standards while the inherent advantage of isotope dilution techniques is utilized for the accurate recovery correction in sample preparation processes. Details of experimental scheme, calculation equation, and uncertainty evaluation scheme are described in this article. The proposed SA-IDMS method was applied to several infant formula samples to test its validity. The method was proven to have a higher-order metrological quality with providing very accurate and precise measurement results.
authors.affiliation: Korea Research Institute of Standards and Science, Yuseong-gu, Daejeon 305-340, Republic of Korea.
authors.forename: Joonhee
authors.initials: J
authors.lastname: Lee
authors.forename: Eun-Sil
authors.initials: ES
authors.lastname: Jang
authors.forename: Byungjoo
authors.initials: B
authors.lastname: Kim
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D003903:Deuterium / Q000737:chemistry*; D006801:Humans; D041943:Infant Formula / Q000737:chemistry*; D007231:Infant, Newborn; D007554:Isotopes / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D011865:Radioisotope Dilution Technique; D053719:Tandem Mass Spectrometry / Q000379:methods*; D024505:Tocopherols / Q000032:analysis*
chemical_list: D007554:Isotopes; D003903:Deuterium; D024505:Tocopherols
keywords: H/D exchange; Infant formula; Standard addition-isotope dilution mass spectrometry (SA-IDMS); Tocopherols