[Bmim]PF6疏水性离子液体敏感膜H2PO4-离子选择性电极测定土壤中总磷含量

Determination of Total Phosphorus Content in Soil by H2PO4- Ion Selective Electrode with Hydrophobic Ionic Liquid Sensitive Membrane of[Bmim]PF6

制备了以1-丁基-3-甲基咪唑六氟磷酸盐([Bmim]PF6)-疏水性离子液体液膜为敏感膜的H2PO4-离子选择性电极(H2PO4--ISE),并在pH 4.66的0.1mol·L-1乙酸-乙酸钠缓冲溶液中,在30℃,以Ag|AgCl|[Bmim]Cl为参比电极,研究该离子电极对H2PO4-的电位响应。试验结果表明:H2PO4-浓度在1.0×10-1~1.0×10-5 mol·L-1内的负对数值,-lg[H2PO4-]与其相应的电位值之间呈线性关系,斜率为-25.4mV·dec-1,响应时间为3min。应用此方法测定了土壤样品中总磷的含量,称取通过0.150mm样筛的土样0.3000g,以少量水湿润后,加入硫酸8mL及高氯酸10滴,混匀后加热消煮至溶液开始转白,继续消煮20min,冷却后加水定容至100 mL,放置过夜,取上清液1.0mL,加入pH 4.66乙酸-乙酸钠缓冲溶液1.0mL,混匀,将H2PO4--ISE插入其中,电极两端分别接至电位计,稳定3min,记录其电位值,所得5个样品的测定值与钼酸铵光度法的测定值基本一致。

An ion selective electrode for H2PO4-(H2PO4--ISE)was prepared by using 1-butyl-3-methylimidazolium hexafluorophosphate(abbrev.as[Bmim]PF6)as hydrophobic ionic liquid sensitive membrane.And its potential response to H2PO4-ion in 0.1 mol·L-1 HAc-NaAc buffer solution of pH 4.66,at 30℃with Ag|AgCl|[Bmim]Cl as reference electrode was studied.As shown by the experimental results,linear relationship was found between values of potentials and-lg[H2PO4-]with concentration of H2PO4-in the range of 1.0×10-1to 1.0×10-5 mol·L-1.Slope of the curve found was-25.4 mV·dec-1,with time of response of 3 min.This method was applied to the determination of total phosphorus in soil samples.The soil sample(0.300 0g)which had passed through sample sieve of 0.150mm,was moistened with small amount of water and 8mL of H2SO4 with 10dreps of HClO4 were added.The mixture was digested by heating until the solution turned to white,and the digestion was continued for 20 min.After cooling,the solution was made up to 100 mL with water and stood overnight.An aliquot of 1.0mL of the supernatant was taken,and 1.0mL of pH 4.66 HAc-NaAC buffer solution was added to the supernatant,and mixed well.The H2PO4--ISE was placed into the solution,with the 2terminals of the ISE connected to the potentiometer,after stablizing for 3min,the potential was recorded.Five soil samples were analyzed by this method,giving values of total phosphorus checked quite well with the results given by the molybdate-photometric method.