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.
,the temperature effect on Nernst slope and influence of PH on determination results, as well as the selection of the total ion strength adjustable buffer solution (TISAB)were studied. PH对测定值的影响； 总离子强度调节缓冲溶液（TISAB）的选择。
In order to reduce the potential drift due to the difference of total ion strength on both sides of the electrode, the internal electrlyte consists of a solution with 0.01 M NH_4Cl and 1 M Na_2SO_4. A determination takes 3-5 min. 氨电极内电解质溶液由0.