Fish otolith reference material for quality assurance of chemical analyses

A certified reference material (CRM) for major, minor and trace element analysis was prepared from sagittal otolith of red emperor (Lutjanus sebae) at National Institute for Environmental Studies (NIES), Japan in collaboration with Western Australian Marine Research Laboratories (WAMRL), Australia. Otoliths (1.4 kg) were cleaned, pulverized, sieved to pass a 105-μm screen and homogenized, and 375 vials, each containing 3 g, were prepared. Certified value was determined for Na, Mg, K, Ca, Sr and Ba through a collaboration involving NIES and five other laboratories. The certified value (mean of the means reported from the collaborating laboratories plus or minus the 95% confidence interval) were 97.0±4.2 μmol/g (0.223±0.010%) for Na, 0.88±0.06 μmol/g (21±1 μg/g) for Mg, 7.21±0.20 μmol/g (282±8 μg/g) for K, 9.69±0.11 mmol/g (38.8±0.5%) for Ca, 26.9±0.5 μmol/g (0.236±0.005%) for Sr and 21.1±0.6 nmol/g (2.89±0.09 μg/g) for Ba. Reference values were given for Cu [12 nmol/g (0.74 μg/g)], Zn [7.2 nmol/g (0.47 μg/g)], Cd [0.025 nmol/g (0.0028 μg/g)] and Pb [0.11 nmol/g (0.023 μg/g)] based on definitive analyses at NIES. This CRM will be of practical value for the quality assurance of solution-based elemental analysis of fish otoliths and other marine aragonites.