## 3 Results
### Low Concentration Effect
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Matrix Type**} & \multirow{2}{*}{**Element**} & \multirow{2}{*}{**Data Quality a**} & \multirow{2}{*}{**n**} & \multicolumn{2}{c}{**Concentration**} & \multirow{2}{*}{**Concentration**} & \multirow{2}{*}{**RSD\% r2**} & \multirow{2}{*}{**t-Test**} & \multicolumn{2}{c}{**Slope z-Test**} & \multicolumn{1}{c}{**Y-Int z-Test**} \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & \\  & & & & & & & & & & \\ \hline \multirow{10}{*}{Cu-Sb} & As & Quantitative & 37 & 8.20–654 & 13–1057 & 7\% & 0.963 * & 0.000 & 0.527 & 0.185 \\  & Cr & Qualitative & 25 & 6.91–182 & 28–156 & 12\% & 0.523 * & 0.021 & 0.721 & 0.720 \\  & Cu & Quantitative & 37 & 10.1–4019 & 17–7739 & 8\% & 0.979 * & 0.000 & 0.641 & 0.201 \\  & Fe & Quantitative & 37 & 3248–49.918 & 3405–44,504 & 1\% & 0.970 * & 0.000 & 0.731 & 0.410 \\  & Hg & Quantitative & 11 & 0.04–473 & 11–720 & 14\% & 0.959 * & 0.127 & 0.802 & 0.637 \\  & Mn & Quantitative & 37 & 138–1227 & 113–1452 & 3\% & 0.929 * & 0.004 & 0.605 & 0.458 \\  & Pb & Definitive & 37 & 14.7–1216 & 12–1156 & 6\% & 0.988 * & 0.760 & 0.770 & 0.524 \\  & Sb & Definitive & 15 & 1.64–1049 & 20–1627 & 9\% & 0.970 * & 0.576 & 0.704 & 0.589 \\  & Zn & Quantitative & 37 & 20.3–1204 & 30–1462 & 4\% & 0.969 * & 0.007 & 0.849 & 0.709 \\ \hline \multirow{10}{*}{Pb-Zn} & As & Quantitative & 52 & 0.91–2693 & 5–2886 & 10\% & 0.856 * & 0.000 & 0.383 & 0.051 \\  & Cr & Qualitative & 5 & 2.04–50.0 & 84–218 & 7\% & 0.100 & 0.007 & 0.035 & 0.000 \\  & Cu & Qualitative & 34 & 0.69–45.0 & 8–50 & 16\% & 0.358 * & 0.000 & 0.024 & 0.001 \\  & Fe & Quantitative & 53 & 99–96,674 & 263–92.931 & 1\% & 0.952 * & 0.000 & 0.201 & 0.003 \\  & Hg & Qualitative & 7 & 0.03–0.12 & 33–280 & 11\% & 0.050 & 0.000 & 0.537 & 0.017 \\  & Mn & Quantitative & 57 & 16.6–1239 & 30–1449 & 7\% & 0.895 * & 0.003 & 0.917 & 0.747 \\  & Pb & Definitive & 58 & 5.05–41,436 & 6–36,853 & 5\% & 0.993 * & 0.370 & 0.789 & 0.718 \\  & Sb & Qualitative & 2 & 0.05–75.0 & 21–84 & - & - & - & - & - \\  & Zn & Definitive & 58 & 10.2–49,752 & 15–56,400 & 4\% & 0.992 * & 0.053 & 0.887 & 0.711 \\ \hline \hline \end{tabular}  
* Data quality levels are defined by [11].
* Significant for \(p\) < 0.001. Different colours identify the three data quality levels.  
\end{table} 
Table 3: Statistical summary of comparability on “lab-prepared” samples (powders). Linear regression and _t_-test performed on log\({}_{10}\)-transformed data. n, number of data; Y-int, Y-intercept. its emplacement or weathering. A similar concentration effect was also observed for the CRMs. The accuracy of the analysis in the case of Cu was found to be low in MESS-4, where Cu is \(<\)100 mg/kg (accuracy = 158-164% and Cu concentration = 32.9 mg/kg), whereas the opposite was observed in PACS-3, where Cu is \(>\)100 mg/kg (accuracy = 111-135% with Cu concentration = 372 mg/kg). Analytical issues in As determination in the Pb-Zn samples appeared to be influenced by both concentration effects and interferences with Pb, as described previously. However, interference caused by high concentrations of Pb appeared to be weaker as concentrations increased.