Studies on the Double-wavelength Spectrophotometric Determination of Zinc in Zinc Preparations with 1-(2-pyridylazo)-2-naphthol and Nonionic Surfacant

Objective:To determine zinc in zinc preparations by the double-wavelength spectrophotometric. Methods:A new double-wavelength spectrophotometric method has been developed for the determination of zinc with 1-(2-pyridylazo)-2-naphthol in HAe-NaAc buffer or NH_3·H_2O-NH_4Cl medium at pH 5.3-9.5 and in the presence of nonionic surfacant-OP.Zinc(Ⅱ)reacts with 1-(2-pyridylazo)-2-naphthol to form a 1:2 complex.The measuring and reference wavelengths are 558 nm and 440 nm respectinely.And the sum of these two peak absorptions shows good linearity with the concentration of zinc.Results:The experimental results shown in the best condition the apparent molar absorptivity was 6.87×10~4L·mol~(-1)·cm~(-1),The detection limit was 7.1× 10~(-7)mol·L~(-1)(A=0.010).which was 1.3 times higher than that of single-wavelength spectrophotometric meth- od.Beer's law was obeyed in the range of 7.1×10~(-7)-1.8×10~(-5)mol·L~(-1)for zinc(Ⅱ).Conclusions:The method is applied to the direct determination of zinc in zinc preparations with satisfactory results.