Isotope pattern deconvolution of different sources of stable strontium isotopes in natural systems


Isotope pattern deconvolution (IPD) was used to determine the contribution of different Sr sources to the Sr isotopic composition of natural samples on the example of sturgeon caviar and otoliths. For this purpose, the Sr isotopic composition of raw and salted sturgeon caviar, otoliths as well as water, fish feed and salt (representing the assumed main contributors to the final isotopic composition of strontium in caviar) were analyzed using MC ICP-MS. The molar fractions and their uncertainties were determined using multiple-linear regression modeling and linear algebra calculations. The optimized approach was applied to caviar and otolith samples of different origin. The Sr isotopic composition of raw caviar and otoliths was formed to 79.8 ± 4.3 % by water and 20.2 ± 4.3 % by fish feed (1 SD, n=5, between sites variation). Deconvolution was possible even when the isotopic difference of the n(87Sr)/n(86Sr) between sources was less than 0.1 %. The influence of salting to the isotopic compostion of processed caviar accounted up to almost 80 % for samples treated with salt containing high concentrations of Sr. The developed methodology provides the basis for the accurate origin determination of samples by n(87Sr)/n(86Sr) isotopic-amount ratios, in cases, where the initial natural signature is modified by known additives.
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