ISO/TS 17951-2:2016 specifies a method for the determination of fluoride in waters, waste waters and effluents by continuous flow analysis (CFA). Any insoluble or complexed fluoride is converted to fluoride ion by an automated continuous flow distillation procedure from sulfuric/phosphoric acid. Fluoride ion in the distillate is measured using flow analysis with lanthanum alizarin complexone and spectrometric detection. This method is applicable to industrial waste waters, effluents, surface waters, ground waters, leachates. When this method is applied to the analysis of drinking water, a heater and a distillation unit is unnecessary. Some drinking water contains high concentration of aluminium and iron. In the case of drinking water, ISO/TS 17951-2:2016 is appropriate to drinking water with low interferences. It is not applicable to samples which contain large amount of suspended matter.

In ISO/TS 17951-2:2016, two working ranges are described:

- working range I: 0,1 mg/l to 1,0 mg/l;

- working range II: 1,0 mg/l to 10 mg/l.

The specification of the calibration solutions are to be adapted accordingly.