Dilutions

December 9, 2022

Dripwaters have commonly been diluted 10x using 2% HNO3 for analysis on ICP-MS (Wong et al, 2011; Tremaine and Froelich, 2013; Owen et al., 2016). This ensures that calcium matrix effects are minimized and TDS are well below 200 ppm. For scraped plate calcite, we assumed stoichiometric calcium concentration (40.0432 wt%, or 400432 ppm) in order to measure ratios instead of concentration. We first calculated the minimum amount of acid needed to dissolve each scraped calcite powder sample. We then added 1 mL 2% HNO3 to ensure complete dissolution, mixed, and allowed the calcite powder to dissolve for 15 minutes before diluting. In order to achieve our desired concentration of 400432 ppm calcium in each plate calcite solution, each sample was diluted ~10000x with 2% HNO3 to 40 ppm [Ca] (see dilutions spreadsheet for more details). Dilutions were performed to reduce TDS load and calcium matrix effects.