分光光度法定量测定柠檬酸及其盐的含量

Quantitative determination of citrate by spectrophotometry method

酸性介质中,柠檬酸(或盐)与Fe3+形成的黄色络合物在光照条件下发生光致变色现象,生成紫红色络合物,采用分光光度法可定量测定柠檬酸及其盐的含量。在冰水浴中,日光照射20 min,阴凉处静置30 min,检测波长为490nm。线性范围为(0～300)mg/L,相对标准偏差(RSD)为0.46%(n=6),检测限为3.46 mg/L。方法直接用于测定柠檬酸法氧化铝生产工艺中的柠檬酸根,其反应后的残留率约为100%,酸化后可重新浸矿。

In acidic medium,a yellow ferric citrate complex was changed into a purple-red complex via photochromic reaction in illumination condition.It was employed in quantitative determination of citrate by spectrophotometric method.In ice water mixture,the complex was radiated by sunlight for 20 min and deposited for 30 min in shade,and the detection wavelength was 490 nm.The linear range is 0～300 mg/L,the relative standard deviation（RSD） is 0.46 %（n=6）,and the detection limit is 3.46 mg/L.The method is simple,sensitive and accurate.It was utilized for determination of citrate in citric acid-based alumina production process.The residual rate of citrate group was about 100 % after reaction,which could be reused as leaching reagent after acidification.