Simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ by using second-derivative spectrophotometry method

A new method of simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ is proposed here by using the second-derivative spectrophotometry method. In pH = 10.35 Borax–NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal–porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0–0.60, 0–0.60, 0–0.40, 0–0.80 and 0–0.48 μg mL−1 for Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+, respectively. The molar absorptivity of these color systems were 1.38 × 105, 1.01 × 105, 3.24 × 105, 1.07 × 105 and 1.29 × 105 L mol−1 cm−1. The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results.