| Parameter | Proficiency testing item N173A | Uncertainty | Proficiency testing item N173B | Uncertainty | Unit |
| Electr. conductivity (25 °C) | 390 | 1 | 527 | 1 | µS/cm |
| Total hardness | 1.383 | 0.016 | 1.89 | 0.02 | mmol/L |
| Alkalinity KS 4.3 (as H+) | 1.344 | 0.018 | 2.58 | 0.04 | mmol/L |
| Hydrogen carbonate | 79.0 | 1.1 | 154 | 3 | mg/L |
| Calcium | 30.3 | 0.5 | 57.5 | 0.9 | mg/L |
| Magnesium | 15.2 | 0.3 | 11.11 | 0.16 | mg/L |
| Sodium | 16.58 | 0.18 | 27.4 | 0.4 | mg/L |
| Potassium | 6.91 | 0.04 | 4.72 | 0.03 | mg/L |
| Nitrate (as NO3) | 24.2 | 0.7 | 42.0 | 0.8 | mg/L |
| Nitrite (as NO2) | 0.0857 | 0.0003 | 0.0304 | 0.0008 | mg/L |
| Ammonium (as NH4) | <0.01 | - | 0.101 | 0.004 | mg/L |
| Chloride | 37.4 | 0.7 | 52.4 | 0.5 | mg/L |
| Sulphate (as SO4) | 41.5 | 0.8 | 16.0 | 0.3 | mg/L |
| Orthophosphate (as PO4) | 0.0385 | 0.0010 | <0.009 | - | mg/L |
| Boron | 0.125 | 0.002 | 0.0957 | 0.0019 | mg/L |
| DOC (as C) | 2.88 | 0.02 | 6.19 | 0.04 | mg/L |
| Total phosphate (as PO4) | 0.0799 | 0.0013 | <0.009 | - | mg/L |
| Free Cyanide | 0.0288 | 0.0002 | 0.0555 | 0.0004 | mg/L |
| Silicon | 3.675 | 0.010 | 2.895 | 0.008 | mg/L |
| Fluoride | 0.565 | 0.003 | 0.419 | 0.002 | mg/L |