- “daily average”: the level or concentration determined on the basis of 24-hour sampling with a proportionate flow
- "monthly average": the value determined on the basis of the composition of all 24-hour samples with a proportional flow rate for the month concerned.
- "limit of detection": the output signal or the concentration above which it may be claimed with a stated level of confidence that a sample differs from a blank sample that does not contain a relevant quantity to be determined.
- "limit of determination": a stated multiple of the detection limit for a concentration of the quantity to be determined that can reasonably be determined with an acceptable level of accuracy and precision. The limit of determination can be calculated using a suitable standard or a suitable sample and can be obtained from the lowest calibration point on the calibration curve, with the exception of the blank.
- “reporting limit”: the value below which a component is reported as unquantifiable (“<“). This is equivalent to at least the limit of determination.
- “reference measurement method”: method that must be used to determine a particular parameter. Unless indicated otherwise, this method is described in the water analysis compendium (WAC). The compendium is a collection of methods for taking samples and carrying out measurements and analyses, which include European (EN), international (ISO) or other standardised methods or methods validated by the reference laboratory of the Flemish Region on behalf of the Government of Flanders. The compendium is approved by ministerial decision and its table of contents is published by excerpt in the Belgian Official Journal.
- "measurement uncertainty": a non-negative parameter that characterises the spread of the quantitative values assigned to a quantity to be measured, based on the information used. The measurement uncertainty specified in Appendix 18.104.22.168, Article 4 is half the length of an interval around the analysis result within which the actual value is expected to lie for a reliability level of 95%, and is expressed as a percentage of the analysis result. The measurement uncertainty is calculated according to a method stipulated by the minister.