Determination of Manganese in Food Grade FeSO_4·7H_2O by Solid Phase Extraction and Flame Atomic Absorption Spectrometry

摘要

A new method for the determination of manganese in food grade FeSO_4·7H_2O samples by flame atomic absorption spectrometry (FAAS) after solid phase extraction was developed. The research showed that when coexistent amount of iron was greater than or equal to 100 times of manganese, the relative error of direct determination of manganese by FAAS was greater than or equal to +5%. Firstly, Fe~(2+) was oxidized to Fe~(3+) by HNO_3. Fe~(3+) was masked by EDTA. Mn~(2+) ions were then adsorbed by strong acid cation exchange fiber (SACEF) in pH 1.5 sample solution for 10 minutes and eluted by 2.5 mol/L HNO_3 for 15 minutes. Iron and manganese can be effectively separated by this method. Under the optimum conditions, the adsorption capacity of SACEF to Mn~(2+) ions was attained to be 9.27 mg·g~(-1). The detection limit of the method was 0.032 μg·mL~(-1). The proposed method was used for determination of manganese in three batches of FeSO_4·7H_2O samples. The contents of manganese were 325 μg/g, 823 μg/g, 772 μg/g respectively. The recoveries were in the range of 96.1%～103% and RSDs (n=5) were less than 3.0%.