Isotope analysis Sample Clauses
Isotope analysis. Prior the isotopic separation using chromatographic column, filtered acidified water samples were evaporated in wide mouth Teflon containers (300 mL volume) placed on teflon- coated hotplate at 80°C located within the isolated polycarbonate box (internal air filtered class A 100). Blank Milli-Q water (apparatus Milli-Q Element Merck Millipore) was routinely evaporated using the same procedure. Precipitates formed at the bottom of containers were digested using the mixture of HNO3, H2O2 and HF following standard procedure of organic-rich solid samples digestion (▇▇▇▇▇ et al., 2007). The digestion products were evaporated and dissolved in HCl or HNO3 ultrapure bidistilled acids before introduction to the column. All sample preparation manipulations were performed in clean room class A10000 and the chromatographic separation was conducted in the laminar hood box class A100 located in the clean room.
Isotope analysis. Fe and Zn isotope measurements were carried out on a Multi-Collector-ICP-MS (Neptune Plus) at Durham University, UK. Samples were introduced through a savillex CF-35 or a CF-50 nebulizer (measured uptake between 33 and 40 µl/min for both) into an ESI SIS glass spray chamber. For each element, a specific pair of sample cones and H-cones were used. For Fe isotope measurements, we used medium-resolution slits that gave a mass resolution around 7000, while Zn required only low-resolution slits. This setup gave a sensitivity of range of 8- 11 V/ppm for Fe and 8-10 V/ppm for Zn depending on the sessions. Cup configuration is displayed in Table 1, evidencing the monitoring of interfering elements for which correction was applied (64Ni interfering of 64Zn and 54Cr on 54Fe). 58Fe is not used because the signal from 58Ni is much greater.
Table 1: Cup configuration for Fe and Zn isotopes analyses.