| Parameter | Proficiency testing item N179A | Uncertainty | Proficiency testing item N179B | Uncertainty | Unit |
| Electr. conductivity (25 °C) | 527 | 2 | 413 | 1 | µS/cm |
| Total hardness | 2.32 | 0.02 | 0.988 | 0.012 | mmol/L |
| Alkalinity KS 4.3 (as H+) | 2.77 | 0.04 | 2.080 | 0.017 | mmol/L |
| Hydrogen carbonate | 166 | 2 | 123.8 | 1.1 | mg/L |
| Calcium | 69.9 | 0.9 | 21.6 | 0.4 | mg/L |
| Magnesium | 14.06 | 0.16 | 10.94 | 0.15 | mg/L |
| Sodium | 11.2 | 0.5 | 42.2 | 0.4 | mg/L |
| Potassium | 5.86 | 0.04 | 7.78 | 0.05 | mg/L |
| Nitrate (as NO3) | 31.6 | 0.9 | 61.1 | 1.3 | mg/L |
| Nitrite (as NO2) | 0.0303 | 0.0010 | 0.0557 | 0.0012 | mg/L |
| Ammonium (as NH4) | 0.0394 | 0.0039 | <0.01 | - | mg/L |
| Chloride | 33.8 | 0.6 | 20.46 | 0.12 | mg/L |
| Sulphate (as SO4) | 49.4 | 0.6 | 17.8 | 0.2 | mg/L |
| Orthophosphate (as PO4) | <0.009 | - | 0.0455 | 0.0042 | mg/L |
| Boron | 0.1508 | 0.0012 | 0.0807 | 0.0005 | mg/L |
| DOC (as C) | 6.25 | 0.03 | 4.07 | 0.02 | mg/L |
| Total phosphate (as PO4) | <0.009 | - | 0.101 | 0.003 | mg/L |
| KMnO4-Index (as O2) | 3.74 | 0.14 | 2.43 | 0.09 | mg/L |