This European Standard specifies an Ion-Selective Electrode method (ISE) after hydrochloric acid treatment for the determination of fluoride from animal feeding stuffs. The content of fluoride (F-) corresponds to that of fluorine (F) specified in Commission Regulation (EU) 574/2011[3].
This European Standard is strictly based on several conventions such as those contained in the following example:
EXAMPLE 0,5 g test portion for extraction of fluoride from animal feeds by means of an acid treatment with 20 ml of 1 mol/l hydrochloric acid solution at ambient temperature (20 °C to 25 ºC) for 20 min. The pH is controlled and adjusted to 5,5 in the buffered test solution before determination of fluoride by ISE using standard addition technique.
The method was successfully tested in an interlaboratory study in concentrations between 100 mg/kg up to 500 mg/kg. If this method is followed strictly, then theoretically all concentrations from 40 mg/kg up to 4 000 mg/kg can be analysed within the linear calibration function.
Only for concentrations lower than 40 mg/kg is the use of an interpolation technique required instead of standard addition Annex C.
The quantification limit for fluoride using the conventions of the method including the standard addition technique is 40 mg/kg or lower than 2,5 mg/kg when using interpolation Annex C.