Water quality -- Determination of fluoride -- Part 1: Electrochemical probe method for potable and lightly polluted water

رقم المستند: NL ISO 10359 1 : 2010
القطاع: Food Technology
TC: NL TC 147
ICS: 13.060.20 - 13.060.50
1 .l Field of application This part of ISO 10359 specifies a method for the determination of dissolved fluoride in fresh, potable and low contaminated water, and some surface wa- ters, using an electrochemical technique. The method is directly suitable for measuring fluoride concentrations from 0,2 mg/1 to 2,0 g/l. After the addition of a known amount of fluoride, concentrations as low as 0,02 mg/1 tan be detected (see 7.3). The method is not suitable for waste waters and in- dustrial effluents; this determination will be the sub- ject of ISO 10359-2. 1.2 Interferences The electrode will respond directly to hydroxide ions. The formation of HF under acidic conditions will re- duce the measured fluoride concentration. Therefore, buffer all test aliquots to a pH between 5 and 7 to prevent such interference. Cations such as Calcium, magnesium, iron and aluminium form complexes with fluoride or precipitates to which the electrode does not respond. Therefore the buffer Solution also con- tains trans-1,2-diaminocyclohexane-N,N,N’,N’-tetra- acetic acid (CDTA) as a decomplexing agent to free bound fluoride. The boron tetrafluoride anion, BF4, is not decomplexed by the addition of buffer. 2