[目的]探讨用孔雀绿比色法测定KCl稀盐溶液浸提磷的适宜条件．[方法]利用标准溶液和不同利用方式的土样，比较不同浸提和显色条件对稀盐溶液-孔雀绿法灵敏度和精密度的影响．[结果和结论]浸提适宜条件如下：土水比为1 g土∶20 mL水，震荡时间为0.5 h，浸提剂（氯化钾）浓度为0.02 mol· L-1；显色体系中各溶质适宜的最终浓度为：H2 SO40.48 mo1· L-1、钼酸铵0.024 mol· L-1、孔雀绿质量浓度为0.06 g· L-1．缔合物最大吸收波长为620 nm，ρ（P）在0～0.2 mg· L-1范围内符合比耳定律，线性回归方程为A＝3.8943C＋0.001（R2＝0.999**，A为D620 nm ，C为磷质量浓度），ρ（ P）检出限为0.002 mg· L-1．测定结果的准确度和精密度均较高，因此本法适宜于氯化钾稀盐溶液浸提液中磷的测定．%[Objective]The method of available phosphorus characterized by phosphorus extracted in KCl dilute-salt solution was studied .[Method] By using standard solution and soil samples from different land use patterns , influences of different conditions during extracting and color-developing stages on the preci-sion and accurancy of dilute-salt solution-malachite green method were studied .[Result and conclusion]The optimum conditions for extraction were as follows:1 g soil∶20 mL water for soil-water ratio , 0.5 h for oscillation , and 0.02 mol · L-1 for concertration of KCl extracting solution; The optimum final concentrations of reagents for the color-developing system were as follows: H2 SO4 0.48 mol · L-1 , (NH4)6Mo7O24· 4H2O 0.024 mol· L-1, malachite green 0.06 g· L-1.The association complex had a maximum absorption wavelength at 620 nm, and Beer ’ s law was obeyed in the P range of 0 ~0.2 mg· L-1 with the linear regression equation being A=3.894 3C+0.001(R2 =0.999**)and P detection limit being 0.002 mg· L-1 , and the method had high accurancy and precision as well .Thus the method is appropriate to determine phosphorus amount in KCl extracting solution .
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