Determination of fluoride in the presence of tetravalent metal ions with an ion-selective electrode: application to raw materials of fluoride glasses
Abstract
The performance of masking reagents, viz., ethylenediamine-N,N,N′,N′-tetraacetic acid, trans-1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid, diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid (DTPA) and triethylenetetramine-N,N,N′,N″,N″′,N″′-hexaacetic acid(TTHA), was studied for the determination of fluoride in the presence of HfIV and ThIV using an ion-selective electrode. Hafnium(IV) was effectively masked using an excess of DTPA at pH 6. TTHA was the best reagent for masking ThIV, while DTPA provided an alternative for fluoride concentrations of <1 × 10–5 mol dm–3. The masking reaction was rapid and contamination from membrane-dissolution was negligible. Fluoride contents in raw materials of fluoride glasses, viz., ZrF4, HfF4, and ThF4, were determined.