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用抗坏血酸-磷钼蓝分光光度法测定烷基磷酸酯中的有效磷。有效磷=总磷-无机磷。考察了检测波长、显色剂用量、硫酸加入量及显色时间等测定条件对测定结果的影响。方法最佳测定条件为:检测波长820nm;硫酸(9.58 mol.L-1)、钼酸铵(60 g.L-1)、抗坏血酸(100 g.L-1)的加入量分别为2.00、2.00、1.00 mL,70℃水浴条件下显色20 min。在该条件下,测定吸光度值与质量浓度呈线性关系,总磷测定回归方程为:A=0.1924ρ+0.0134,相关系数r=0.999 5;无机磷用正戊醇萃取法测定,回归方程为:A=0.1846ρ+0.0094,相关系数r=0.999 1。方法回收率为91%~97%,RSD小于3.4%。该方法操作简单、计算方便,有望应用于磷酸酯生产的质量控制。
Determination of Available Phosphorus in Alkyl Phosphate by Ascorbate - Phosphomolybdate Blue Spectrophotometry. Effective phosphorus = total phosphorus - inorganic phosphorus. The influence of the measurement conditions such as the detection wavelength, the amount of developer, the amount of sulfuric acid added and the color development time were investigated. The optimum conditions for the determination were as follows: the detection wavelength was 820 nm; the additions of sulfuric acid (9.58 mol·L-1), ammonium molybdate (60 gL-1) and ascorbic acid (100 gL- 70 ℃ water bath for 20 min. Under these conditions, the absorbance value was linear with the mass concentration. The regression equation of total phosphorus was: A = 0.1924ρ + 0.0134, correlation coefficient r = 0.999 5; The inorganic phosphorus was determined by n-amyl alcohol extraction method, the regression equation was: A = 0.1846ρ + 0.0094, correlation coefficient r = 0.999 1. The recovery rate was 91% ~ 97% with RSD less than 3.4%. The method is simple and easy to calculate, which is expected to be applied to the quality control of phosphate ester production.