摘要
提出了紫外可见分光光度法测定土壤中有效磷含量的方法.取经过风干研磨并且过1 mm筛的土壤样品2.5 g,置于100 mL具塞离心管中,加入50.0 mL碳酸氢钠提取剂,于(25±1)℃超声10 min,于(25±1)℃以转速8 000 r·min-1离心5 min.取10 mL上清液用水定容至50 mL,加入5.0 mL钼锑抗显色剂,置于恒温振荡器中振荡1 min,再加入10 mL水,振荡1 min,于25℃静置30 min后,用1 cm光径比色皿在波长880 nm处,以磷标准溶液系列的零点为参比进行比色测定.结果表明:磷的质量浓度在1.0 mg·L-1以内与对应的吸光度呈线性关系,检出限(2.528s)为0.107 mg·kg-1;方法用于分析4个浓度水平的土壤有效态成分分析标准物质,测定值均在认定值的不确定度范围内,并且测定值的相对标准偏差(n=6)均小于5.0%;方法用于淫羊藿实验田施肥前后土壤样品的分析,测定结果与NY/T 1121.7-2014的基本一致.
Abstract
A method for determination of available phosphorus in soil by ultraviolet-visible spectrophotometry was proposed.2.5 g of soil sample that had been air dried,grounded and sieved through a 1 mm-sieve was taken into a 100 mL-centrifuge tube with a stopper.50.0 mL of sodium bicarbonate extractant was added,and the mixture was sonicated for 10 min at(25±1)℃and centrifuged at a rotational speed of 8 000 r·min-1 for 5 min at(25±1)℃.10 mL of the supernatant was taken and made its volume up to 50 mL with water,and 5.0 mL of molybdenum antimony anti-chromogenic agent was added.It was placed in a constant temperature oscillator and shaked for 1 min.10 mL of water was added and the mixture was shaked for 1 min.After settling at 25℃for 30 min,colorimetric measurement was performed at a wavelength of 880 nm in 1 cm diameter colorimetric dish with the zero concentration point of the phosphorus standard solution series as the reference.As shown by the results,linear relationship between absorbance and mass concentration of phosphorus was found within 1.0 mg·L-1,with detection limit(2.528s)of 0.107 mg·kg-1.This method was used to analyze the standard substances of effective soil component analysis at 4 concentration levels,and the determined values were all within the uncertainty range of the certified values,with RSDs(n=6)of the determined values less than 5.0%.This method was also used to analyze soil samples before and after fertilization in epimedium experimental field,and the determined results were basically consistent with those by NY/T 1121.7-2014.
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