Quantification of the diagenesis-designating metals in sediments by ICP-MS: Comparison of different sample preparation methods

Abstract

Concentrations of specific metals in sediments are of immense importance in geochemical studies related to diagenetic processes, and quantification can be most reliably performed by ICP-MS after bringing the sample into solution. It is the latter analytical operation that generates a discord as no common sample preparation approach has been yet accepted. To resolve this challenge, we compared different modes of acidic sample digestion (in open and closed systems, applying in the latter case conventional or microwave heating) using a lake sediment reference sample. It was shown that the sample treatment in an autoclave with resistance heating provides the best fit (relative deviation < 7%) to certified values for metals generally used as diagenetic proxies (U, Sm, Nd, Th, La, Sc, Sr, etc.). Furthermore, the thermally convective pressure digestion appears to be more cost-efficient than microwave-assisted digestion (because of lower reagent consumption and cheaper removable PFE liners), an important asset for systematic geochemical mapping. In order to prove the applicability of the developed digestion procedure for different sediments, a marine sample from the East Siberian Sea was analyzed independently in two laboratories and across all representative metals the results acquired were found in good agreement.