Spectrophotometric method for determination of germanium in foods with new color reagent trimethoxylphenylfluorone Original Research Article

A high sensitive and selective spectrophotometric method for determination of germanium has been developed. The method is based on the reaction of germanium with a new reagent trimethoxylphenylfluorone (TMPF) in the presence of Triton X-100. The absorbency of the complex (λmax=505 nm) increases linearly with concentration up to 0.24 μg ml−1 germanium in aqueous solution with a relative standard deviation (R.S.D.) of 1.02%. The molar absorptivity of the germanium complex, the limit of quantification and limit of detection were found to be 1.7×105 l mol−1 cm−1, 0.70 and 0.21 ng ml−1, respectively. The influences of metal ions on the determination of germanium were investigated; all foreign ions studied, could be tolerated in considerable amounts, 50 mg of Ca and Mg, 100 mg of Fe and Al, 60 mg of Ni, 8 mg of Mn and 1.0 mg of Pb do not interfere with the determination of 1.0 μg of germanium, so the selectivity is superior to published methods, especially, with regards to Ti, Zr, Sn, Mo and W, which always interfere with the determination of germanium in other methods. The color reaction system is simple and stable. The reaction of germanium with TMPF is complete within 30 min and the absorbency of the complex remains almost constant for at least 24 h in a phosphoric acid medium. In addition, the synthesis of trimethoxylphenylfluorone and the preconcentration of low germanium concentrations were also investigated in detail. The proposed method has been applied to determine traces of germanium in foods with satisfactory results.