Methodology
Overview
Two independent methods were used to measure TE/Ca: one for dripwaters and one for scraped plate calcite. In the dripwater method, concentrations of each analyte (including calcium) were measured in ppb. Each TE concentration was then divided by the corresponding [Ca] to achieve the TE/Ca ratio. Calcium concentrations in plate calcite were assigned using the stoichiometric calcium concentration of calcite (400432 ppm). Measurements were calculated using TE/Ca ratios determined in our calibration standards. No concentration data was obtained, only TE/Ca ratios directly, and calcium was not measured since it was assigned. We created this method in order to minimize time and any error associated with completing two separate dilutions, as well as avoiding measuring calcium during analysis since interferences are so strong at and around mass 40. In the past, two dilutions were performed in order to measure both trace elements and calcium. Using this new method, the TE/Ca ratios can be obtained directly, minimizing sample preparation time, run time, and error associated with double-dilution correction. Though, due to the extremely small masses of powders being measured (100-1000 µg), there are possibilities of major error propagation due to weighing precision.