Towards the certification of the purity of calibrant reference materials for thyroid hormones: A chicken and egg dilemma

• Published in: Journal of Chromatography A Vol. 1156; no. 1; pp. 236 - 248
• Main Authors: Toussaint, B., Schimmel, H., Klein, C.L., Wiergowski, M., Emons, H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 13.07.2007; Elsevier
• Subjects: Biological and medical sciences; Calibrant; Calibration - standards; Certification; Chromatography, High Pressure Liquid - methods; Drug Stability; Investigative techniques, diagnostic techniques (general aspects); Mass Spectrometry; Medical sciences; Miscellaneous. Technology; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Purity; Reference material; Reference Standards; Spectrophotometry, Ultraviolet; Thyroid hormones; Thyroid Hormones - standards; Thyroxine - standards; Triiodothyronine - standards; Uncertainty; Wettability; Reference material; Purity; Thyroid hormones; Certification; Calibrant; Chemical analysis; Coupled method; HPLC chromatography; Purity control; Calibration; Certified reference material; Ultraviolet detector; Clinical biology; Quality control; Thyroid hormone; Mass spectrometry; Quantitative analysis
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2006.11.095

The certification of the purity of CRMs intended for calibration, where no other certified material already exists for comparison, raises principle questions on how to determine the purity of a “first” calibrant in the calibration hierarchy. We developed and certified two calibration CRMs for their purity in thyroid hormones taking into consideration inorganic residues, residual solvents and organic impurities detectable by HPLC–UV and HPLC–MS. IRMM-468 was certified for a thyroxine (T 4) mass fraction of 98.6 ± 0.7% and IRMM-469 was certified for a 3,3′,5-triiodothyronine (T 3) mass fraction of 97.1 ± 0.7%. The approach we used aims to determine the purity of these two CRMs to the best of our knowledge and taking all scientific aspects properly into account for the estimation of an uncertainty related to the stated purity.