Determination of magnesium isotopic ratios of biological reference materials via multi-collector inductively coupled plasma mass spectrometry

Rationale Despite a wide range of potential applications, magnesium (Mg) isotope composition has been so far sparsely measured in reference materials with a biological matrix, which is important for the quality control of the results. We describe a method enabling the chemical separation of Mg in geological and biological materials and the determination of its stable isotope composition. Methods Different geological (BHVO-1, BHVO-2, BCR-1, and IAPSO) and biological (SRM-1577c, BCR-383, BCR380R, ERM-CE464, DORM-2, DORM-4, TORT-3, and FBS) reference materials were used to test the performance of a new sample preparation procedure for Mg isotopic analysis. The procedure consisted of a simple three-stage elution method to separate Mg from the matrix. Mg isotopic analyses were performed in two different laboratories and with three different multi-collector inductively coupled plasma mass spectrometry instruments. Results The biological reference materials show a wide range of delta Mg-26 values (relative to DSM3 standard), spanning over 2 parts per thousand, from 0.52 +/- 0.29 parts per thousand (2SD, n = 7) in bovine liver (SRM-1577c) to -1.45 +/- 0.20 parts per thousand (2SD, n = 5) in tuna fish (ERM-CE464), with an external precision of 0.03 parts per thousand (2SD, n = 85). Conclusions This study indicates that isotopic measurements of Mg in biological reference materials show good performance, with the results being within the accepted range. We confirmed that delta Mg-26 values in liver are the most positive of all biological materials reported so far.