in the present work three ferroin reagents were studied for the simultaneous spectrophotometric determination of iron and copper: 1,10-phenanthroline, 2,2'-bipyridine and 2,4,6-tri(2-pyridyl)-1,3,5-triazine. effect of ph, conditions, order reagent addition, interferences, amount of reagents, lineal range, sensitivity and stability of each system were compared. the 2,4,6-tri(2-pyridyl)-1,3,5-triazine can be used for determination of iron in the presence of copper with a detection limit of 5 μg l-1 and coefficient of variation of 2.0%; however it was not possible to determine directly copper in the presence of iron with this reagent. 1,10-phenanthroline can be used for simultaneous determination of the metallic ions with detection limits of 7 and 8 mg l-1 and coefficients of variation of 1.8 and 2.3% in the determination of iron and copper, respectively. the results showed also that 2,2'-bipyridine can be used for simultaneous determination of the metallic ions with detection limits of 11 and 32 μg l-1 and coefficients of variation of 1.9 and 2.5% in the determination of iron and copper, respectively. the reagents were used for spectrophotometric determination of iron and copper in ethanol fuel.
