| Parameter | Proficiency testing item M173A | Uncertainty | Proficiency testing item M173B | Uncertainty | Unit |
| Aluminium | 58.4 | 0.5 | 24.4 | 0.3 | µg/L |
| Arsenic | 3.33 | 0.02 | 4.20 | 0.03 | µg/L |
| Lead | 0.806 | 0.014 | 3.69 | 0.03 | µg/L |
| Cadmium | 1.765 | 0.014 | 0.705 | 0.007 | µg/L |
| Chromium | 3.79 | 0.03 | 1.72 | 0.03 | µg/L |
| Iron | 17.92 | 0.19 | 57.5 | 0.3 | µg/L |
| Copper | 3.43 | 0.03 | 107.8 | 0.4 | µg/L |
| Manganese | 10.79 | 0.16 | 44.6 | 0.2 | µg/L |
| Nickel | 5.50 | 0.04 | 1.92 | 0.03 | µg/L |
| Mercury | 0.421 | 0.013 | 1.588 | 0.017 | µg/L |
| Selenium | 2.83 | 0.02 | 0.404 | 0.017 | µg/L |
| Uranium | 5.24 | 0.04 | 2.64 | 0.02 | µg/L |
| Zinc | 10.5 | 0.7 | 20.1 | 0.7 | µg/L |