Micro-emulsion Spectrophotometric Determination of Iron in Aluminum Alloy by the Associated System of Fe(Ⅲ)-Thiocyanate-Ethyl Rhodamine B

A micro-emulsion spectrophotometric method for determination of iron in aluminum alloy was proposed. Fe (Ⅲ) was reacted with 3.00 mL of 2 mol·L-1 KSCN solution and 3.00 mL of 1.0×10-3mol·L-1 ethyl rhodamine B in 0.5 mol·L-1 H2SO4 solution in the presence of 0.8 mL of 5 g·L-1 gum arabic and 0.70 mL of micro-emulsion solution. An association complex was formed between the anionic complex of ［Fe(CN)6］3- and the cation of ethyl rhodamine B (ERB+), which was solubilized by solutions of gum arabic and micro-emulsion. Linear relationship between values of absorbance and mass concentration of Fe(Ⅲ) was found in the range of 0.026-0.36 mg·L-1. Apparent molar absorptivity of the associated system found was 1.08×105L·mol-1·cm-1 at the wavelength of its absorption maximum 620 nm. The proposed method was applied to the determination of Fe in samples of aluminum alloy, giving values of RSD′s (n=5) less than 2%.