Reaction of mercury(II)-thiosalicylate complex with picolinic acid and ultraviolet spectrophotometric determination of mercury(II)

Abstract

The monothiosalicylate complex of mercury(II) reacts with picolinic acid (PIC) to form a ternary complex which has an absorption maximum at 295 nm in 50%V/V ethanol-water in the pH range 6.3–7.5. Beer's law is obeyed up to a 20.15 µg ml^–1 concentration of Hg^II. The molar absorptivity of the ternary complex is 0.86 m² mol^–1 at 295 nm and the sensitivity for the Hg^II ion is 5.2 × 10^–3µg cm^–2 per 0.001 absorbance unit. The composition of the ternary complex is estimated to be Hg(TSA)(PIC). A number of ions which interfere with the determination could be masked by the addition of EDTA or fluoride ions as masking agents. Further information on the complex-forming equilibria and stability of the Hg^II ternary complex was obtained by potentiometric titrations at 20 ± 0.1 °C and 0.1 M(NaClO₄) ionic strength.