杂多酸示波极谱法测定磷酸根

Single-sweep Polarographic Determination of Phosphate on the Use of Its Heteropoly Acid Complex

在pH=1的HCl和25mg/ml抗坏血酸存在的溶液中,磷酸根和钼酸根形成具有极谱活性的磷钼杂多酸。该杂多酸在NH_3-NH_4Cl(pH=9.9)底液中产生—灵敏极谱还原波,其峰电位为-1.12V(vs.SCE)。导数波高与磷酸根浓度在5×10^(-8)～4×10^(-5)mol/L范围内呈良好的线性关系,检测下限2×10^(-8)mol/L。利用反应速度的不同消除了大量硅酸根的干扰。文中对极谱波的性质做了初步研究。

In 0. 1 mol/L HC1 solution containing ascorbic acid, phosphate can speedily react with molybdate. The reaction product can be reduced with a sensitive wave at the Ep of about - 1. 12 V (vs. SCE) in NH3-NH4Cl buffer solution (pH = 9. 9). The derivative peak height is directly proportional to the phosphate concentration in the range of 5×10-8-4×10-1 moI/L,and the detection limit is 2×10-3 mol/L. At least the presence of one hundredfold ratio of silicate does not interfere with the determination of phosphate. The method is applied to the determination of phosphate in soil with satisfactory results. The behavior of the po-larographic wave has also been studied.