The Natural Mineral Water, Spring Water and Bottled Drinking Water (Wales) Regulations 2007

Regulation 7(2)

SCHEDULE 7 Performance characteristics for analysing the constituents in Schedule 6

Constituent	Accuracy of parametric value in %	Precision of parametric value	Detection limit of parametric value in %
Notes: 1. The method of analysis used to measure the concentration of the constituents in Schedule 6 must be capable of measuring concentrations equal to the parametric value with the specified accuracy, precision and detection limits. 2. Regardless of the sensitivity of the method of analysis, the result must be expressed to at least the same number of decimal places as the maximum limit set out in Schedule 6 for the particular constituent being analysed. 3. Accuracy is the systematic error and represents the difference between the average value of a large number of repeated measurements and the exact value. 4. Precision represents the random error and is expressed in general as the standard deviation (within a batch and between batches) of a sample of results from the average. 5. Acceptable precision is equal to twice the relative standard deviation. 6. The detection limit is— (a) three times the relative standard deviation within a batch of a natural sample containing a low concentration of the constituent; or (b) five times the relative standard deviation within a batch of a virgin sample. 7. The method should make it possible to determine cyanide in all its forms.
Antimony	25	25	25
Arsenic	10	10	10
Barium	25	25	25
Cadmium	10	10	10
Chromium	10	10	10
Copper	10	10	10
Cyanides	10	10	10
Fluoride	10	10	10
Lead	10	10	10
Manganese	10	10	10
Mercury	20	10	20
Nickel	10	10	10
Nitrate	10	10	10
Nitrite	10	10	10
Selenium	10	10	10