The standard applies to the examination of water with an anionic detergent content of at least 0.1 mg/l, expressed as lauryl sulphate. The mentioned lower limit applies when using a cuvette with a light path of 10 mm. According to the described method, that part of the anion-active substances present is determined that is not bound by cation-active substances. Non-ionic detergents are not determined. Larger amounts of organic substances may interfere with the determination. Interference due to sulphide can be eliminated by adding hydrogen peroxide (see 7.2).
NEN 6674-1981 history
1981NEN 6674-1981 Waste water - Photometric determination of anionactive detergents