Quality Control Standards

December 9, 2022

Aside from each set of six calibration standards, a second quality control standard was created by serially diluting a separate stock of standards to a median concentration for each method. Doing so verifies the concentration of each analyte in our unknowns and calibration standards. Below is one of the B-check quality control analyses. Average/actual of 1 represents perfect recovery. Many of our analytes experienced higher recoveries in our plate calcite analysis, but we have not discovered the root cause.

Table 5: B-check quality control recovery for scraped plate calcite

For both dripwaters and plate calcite, we also measured the NIST 1643f standard multiple times throughout each analysis to independently confirm accuracy and precision and measure drift. Below is one of the NIST 1643f quality control analyses. Average/actual of 1 represents perfect recovery. Our recoveries for dripwaters were close to ideal.

Table 6: NIST 1643f quality control recovery for dripwaters

Since NIST-1643f is used as a standard for trace elements in water and not as a solid, we measured two additional carbonate standards in order to confirm accurate measurements throughout the plate analysis. These standards from USGS and NRCC (MACS-3 and FEBS-1, respectively) allowed us to further measure the accuracy of our ICP-MS calibration and measurements. It is notable to note that these standards are not speleothem-specific carbonates, and FEBS-1 is poorly characterized, so we will likely use a more specific reference standard in the future. 

Table 7: MACS-3 quality control recovery for plate calcite

Table 8: FEBS-1 quality control recovery for plate calcite