| Element | Numerical model | r2 |
| Mg | Mg = 864.40 + 527.38 (DGR) − 859.30 (DGR)2 | 0.870 |
| Al | Al = 516.18 + 498.18 (DGR) − 79.41 (DGR)2 | 0.702 |
| Zn | Zn = 28.80 + 81.94 (DGR) − 15.40 (DGR)2 | 0.936 |
| Mn | Mn = 30.56 + 4.79 (DGR) |
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