水相分光光度法测定土壤中有效铜

Spectrophotometric determination of soil available copper in aqueous system

开发了一种铜试剂（二乙基二硫代氨基甲酸钠，DDTC）水相分光光度法测定土壤有效铜的方法。利用阿拉伯树胶做增溶剂，柠檬酸-EDTA溶液做干扰掩蔽剂，DDTC能够与铜离子形成稳定的黄色络合物，可直接在水溶液中进行分光光度法测定。络合物的最大吸收波长为454nm，摩尔吸光系数为1．02×10^4L·mol^-1·cm^-1，铜含量在0～4μg／mL范围内符合比尔定律，线性相关系数r=0．9996，方法检出限为0．031μg／mL，平均回收率104．8％，RSD为3．2％。本法对红壤加铜培养实验的测定结果表明，土壤有效铜含量与土壤加铜水平呈线性相关，与电感耦合等离子发射光谱法（ICP．AES）相比，有效铜含量和相对标准差均无显著差异。

Experiments of direct photometric determination of soil available copper with sodium diethyldithiocarbamate in aqueous solution was conducted to explore a simple method to determine soil available copper. The results showed that the reaction of DDTC with Cu （ U ） could form a kind of stability yellow complex and could be directly determined by the spectrophotometry with the help of Arabic gum as a solubilizing agent and ammonium citrate-EDTA as a masking agent. The complex showed maximum absorbance at the wavelength of 454, the apparent molar absorption coefficient ε was 1.02 × 10^4L · mol-1 ·cm-1 while the Beer＇ s law was obeyed for copper content in the range of 0 ~ 4 μg/mL, and the linear correlation coefficient, the detection limit, average recovery and RSD were 0. 9996, 0. 031 μg/L, 104.8% and 3.2%, respectively. No significant difference at available copper content and RSD with inductively coupled plasma atomic emission spectrometry （ICP-AES） was found, this method was used to determine available copper in soil samples incubated by copper additions, and the results showed soil available copper was linear significantly correlated with copper additions in soil. In summary, with simple operation, easy to get the necessary reagents, no need of expensive instruments, and the satisfactory exactitude and accuracy for determination of soil available copper, this method was cheap and worth to popularize in determining soil available copper.