A double-spike MC TIMS measurement procedure for low-amount Ca isotopic analysis of limited biological tissue samples

• Published in: Analytical and bioanalytical chemistry 2022, Vol.414 (1), p.675-689
• Main Authors: Retzmann, A., Walls, D., Miller, K. A., Irrgeher, J., Prohaska, T., Wieser, M. E.
• Format: Article
• Language: English
• Subjects: ABCs 20th Anniversary; Algorithms; Analytical Chemistry; Biochemistry; Biomedical materials; Bone turnover; Calcium isotopes; Characterization and Evaluation of Materials; Chemical analysis; Chemical Fractionation; Chemistry; Chemistry and Materials Science; Data reduction; Food Science; Fractionation; Hair; Hair - chemistry; Humans; Ionization; Isotopes - analysis; Laboratory Medicine; Mass spectrometry; Mass Spectrometry - methods; Mass spectroscopy; Metabolism; Monitoring/Environmental Analysis; Reference materials; Research Paper; Seawater; Tissues; Water analysis
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-021-03650-8

The application of Ca isotopic analysis in biomedical studies has great potential to identify changes in Ca metabolism and bone metabolism. Reliable measurement of Ca isotope-amount ratios is challenging considering limited Ca amounts and significant procedural blank levels. In this study, Ca purification was performed using the DGA Resin, optimized for low procedural blanks and separation of Ca from matrix elements and isobaric interferences (Na, Mg, K, Ti, Fe, Ba), while maintaining quasi-quantitative recoveries which are sufficient since a 42 Ca– 48 Ca double-spike (DS) was applied. Ca isotopic analysis was performed using multicollector thermal ionization mass spectrometry (MC TIMS). The obtained procedural Ca blank of ≤10 ng enables processing of limited Ca amounts down to 670 ng. Data reduction of the measured Ca isotope-amount ratios was performed using an in-house developed software solving the DS algorithm. Data quality was improved by extension of equilibration time of the sample-DS mixture and implementation of a normalization strategy for raw isotopic data. The reported δ ( 44 Ca/ 40 Ca) NIST SRM 915a of NIST SRM 915a processed as a sample was found to be 0.01 ‰ ± 0.08 ‰ (2 SD , n  = 15). Ca isotope-amount ratios of the reference material NIST SRM 1400 (bone ash), NIST SRM 1486 (bone meal), GBW07601 (human hair), and IAPSO (seawater) were in good agreement within uncertainty with literature data. Novel data on additional reference materials for biological tissues (hair) is presented, which might indicate a potential fractionation of Ca incorporated into hair tissue when compared to the blood pool. Graphical abstract