Spectrofluorimetric determination of picogram level Pb(II) using a dimercaptothiadiazole fluorophore

This paper describes the spectrofluorimetric determination of picogram level Pb(II) using 2,5-dimercapto-1,3,4-thiadiazole (DMT) as a fluorophore. Excitation of DMT at 330 nm shows an emission maximum at 435 nm. The colorless solution of DMT changes into highly emittive yellow color immediately after the addition of 0.5 μM Pb(II) and nearly 245-fold increase in emission intensity at 435 nm was observed. These changes were attributed to the complex formation between Pb(II). The emission intensity linearly increases in the concentration range of 10–100 nM Pb(II) and DMT. Based on the fluorescence enhancement, the concentration of Pb(II) was determined. Interestingly, the emission intensity was increased even in the presence of 0.1 pM Pb(II). The fluorophore showed an extreme selectivity towards 100 nM Pb(II) even in the presence of 50,000-fold higher concentrations of common metal ions interferences such as Na+, K+, Ca2+, Mg2+, Fe2+, Cd2+, Cr3+, Mn2+, Zn2+, Co2+, Ni2+ and 5000-, 100- and 40-fold of Cu2+, Hg2+ and Ag+ ions, respectively. The lowest detection of 20 pg L−1 Pb(II) was achieved for the first time using DMT. The proposed method was successfully utilized for the determination of Pb(II) in tap water, polluted river water and industrial waste water samples. The results obtained in the present study were validated with both AAS and ICP-AES methods.

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► 2,5-Dimercaptothiadiazole was used as a fluorophore to determine picogram Pb(II).
► The emission intensity of fluorophore was increased after the addition of Pb(II).
► Selective determination of Pb(II) was achieved in the presence of interferences.
► Detection limit of 20 pg was achieved by the present method.
► The results obtained in the present study were validated with ICP-AES method.