Penghilangan Interferensi Fe dan Mn dengan Ekstraksi Pelarut pada Penentuan Co dan Cu dalam Pirolusit Menggunakan Spektrometri Serapan Atom

Abstract

Research on the removal of Fe and Mn interference by solvent extraction on the determination of Co and Cu in pyrolusite using atomic absorption spectrometry with an air-acetylene flame have been investigated. Dissolution of pyrolusite sample was done by wet destruction method with solution of aqua regia and HF in the ratio of 3:4 (v/v). Interference studies were carried out for the absorbance of Co and Cu with the addition of iron and manganese in the concentration range 100-1000 ug/mL for iron and 100-5000 ug/mL for manganese measured at the wavelength 240.7 nm and slit width 0.2 nm for Co and wavelength 324.7 nm and slit width 0.7 nm for Cu.

The results showed that Fe at concentrations of 100-1000 ug/mL and Mn at the concentrations of 100­5000 ug/mL could interfere the absorbance of Co and Cu, i.e. increase the absorbance of Co and decrease the absorbance of Cu. The interference of Fe can be overcome by solvent extraction with methyl isobutyl ketone in 7 M HCl medium. The interference of Mn can be overcome by masking with 0.10 M EDTA, then Co and Cu were extracted into chloroform by complexing them with sodium diethyldithiocarbamate at pH 2. The content of Fe and Mn in the pyrolusite measured by AAS were 67.35±0.61 mg/g and 545.00±6.25 mg/g, respectively. The content of Co and Cu before extraction were 773.33±25.17 ug/g and 2166.67±101.04 ug/g, respectively and after extraction were 487.18±11.10 ug/g and 2733.33±80.36 ug/g, respectively. These results have high precision with relative standard deviation (RSD) value of each elements less than 5%.