Trace determination of zinc in soil and vegetable samples by spectrophotometry using pyridoxal thiosemicarbazone and 2-acetyl pyridine thiosemicarbazone

The rapid and continuous progress in trace analysis of metals is associated with development of several new techniques such as spectrophotometry. Thiosemicarbazones have been used as chromogenic reagents in spectrophotometric determination of metals. In this study the synthesis and characterization of pyridoxal thiosemicarbazone (PDT) and 2-acetyl pyridine thiosemicarbazone (2-APT) using IR, MS, and 1HNMR were conducted. Zn(II) forms yellow colored complex with PDT and 2-APT in the pH range of 5–7 at 430 nm, and 8–10 at 360 nm, respectively. The Zn(II)PDT and Zn(II)-2-APT complexes obeys Beer’s law in the concentration range of 0.26– 2.62 and 0.25–2.56 μg/mL, respectively. The molar absorptivity and Sandell’s sensitivity of Zn(II)-PDT and Zn(II)-2-APT complexes are 1.8 x 104 L/mol.cm and 0.0035 μg/cm2, 2.9 × 104 L/mol.cm and 0.0167 μg/cm2, respectively. A first derivative spectrophotometry method is proposed for the determination of Zn(II) in the range 0.06–2.94 and 0.05–2.72 μg/mL of Zn(II) using PDT and 2-APT, respectively. The first derivative spectrum of Zn(II)-PDT and Zn(II)-2-APT complexes exhibits maximum amplitude at 400 and 385 nm, respectively The method was tested for Zn(II) determination in soil and vegetable samples. Using paired sample t-test at 0.05 level, the results were in good agreement with those obtained using flame atomic absorption spectrophotometer. Subjects: Analytical Chemistry; Chemical Spectroscopy; Environmental Chemistry