The ash of samples was soaked and dissolved in 0. 5 mol/L HC1. After the addition of total ion strength adjustment buffer(TISAB) , the fluoride contents were detected with the fluoride selective electrode.

• 灰分用0.；5mol/L HCl浸泡；加入总离子强度调节缓冲剂(TISAB)后用氟电极测定氟。