Fluorimetric Determination of Mercury(II) Based on its Reaction with Iodide and Triphenylmethane Compounds

A fluorimetric method for the determination of Hg2+ (5–100 ppb) was developed based on the reaction between triphenylmethane cations (Brilliant green, Malachite green and Crystal violet) and tetraiodo-mercurate(II). This reactioon gives ion-associated complexes with strong fluoresence at 521 nm after excitation at 256 nm. Optimum concentrations for Brilliant green, Malachite green and Crystal violet were 15, 10 and 2 mg/l, respectively. The optimum pH for complex formation was 3.0 for Brilliant green and Malachite green, and 2.0 for Crystal violet. The detection limit for the method defined as 3 σ [sgrave] was found to be 0.72 μg/1 of Hg2+. Ions that interfere in the determination of mercury by the proposed method are Ag(I), Pt(II), Cd(II), Bi(III) and Ti(IV). Titanium(IV), Ag(I) and Bi(III) can be masked whereas the interference of Pt(II) and Cd(II) cannot be overcome as yet.