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    纳氏试剂分光光度法测定土壤中全氮含量

    Nessler′s Reagent-Spectrophotometric Determination of Total Nitrogen in Soil

    • 摘要: 提出了纳氏试剂分光光度法测定土壤中全氮含量。以硫酸铜为加速剂,用硫酸对土壤样品进行消解。消解完毕的溶液用400 g·L-1氢氧化钠溶液调节其酸度至pH 10左右,溶液与沉淀一起移入容量瓶中,定容至200 mL。移取上清液10 mL于50 mL比色管中,加入酒石酸钾钠溶液作掩蔽剂,加入纳氏试剂显色后,加水定容,于波长420 nm处测量其吸光度并计算土壤样品中全氮含量。氮的质量浓度在2 mg·L-1以内与吸光度呈线性关系。方法用于土壤样品分析,测定值与滴定法测定值相符,测定值的相对标准偏差(n=10)为0.24%;回收率在92.3%~112%之间。

       

      Abstract: A method for the determination of total nitrogen in soil by Nessler′s reagent-spectrophotometry was proposed. The soil sample was digested with H2SO4 using CuSO4 as accelerator. Acidity of the sample solution was adjusted to ca. pH 10 by addition of 400 g·L-1 NaOH solution, and the solution together with precipitate was made up to 200 mL in a volumetric flask. An aliquot of 10 mL of the supernatant was taken and placed in a 50 mL colorimetric tube, sodium potassium tartrate solution was added as complexing agent and Nessler′s reagent added as coloring agent, and made up to 50 mL with water. Its absorbance was measured at the wavelength of 420 nm, and the content of total nitrogen was calculated. Linear relationship between values of absorbance and mass concentration of nitrogen was kept in the range within 2 mg·L-1. The proposed method was applied to the analysis of soil samples, giving results in consistency with those obtained by titrimetry with RSD (n=10) of 0.24%. Values of recovery were found in the range of 92.3%-112%.

       

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