The standard applies to all types of water. Dis urbing amounts of organic substances are destroyed during the pretreatment. Vanadium is an irritant if its content is more than ten times that of chromium. In concentrations above 1mg/l, iron gives a yellow color, which, however, is not very dis urbing when measured at the correct wavelength. Dis urbing amounts of iron, copper and vanadium can be removed by extraction of the cupferrates with trichloromethane.
NEN 6485-1983 history
1983NEN 6485-1983 Water - Photometric determination of chromium content