Figure of the main text illustrates this function alongside key statistical measures. Additional regression statistics are tabulated in Tables , and S4. The statistics reveal that the regressed line equation poses a good fit to the calibration data overall: Residuals are scattered randomly around zero, thus showing no significant trend or spread with concentration. Additionally, the R and R2 values lie close to 1, which confirms a strong of degree of positive linear correlation between the y and x variables. Potential systematic errors in the established calibration curve arising from uncertainties associated with the purity of the reference materials used in standard preparation have not been evaluated and will not be considered in experimental data analyses.