Based on the lacuna identified in the literature, new of reagents viz, 2-acetylpyridine thiosemicarbazone (I), 2-acetylpyridine semicarbazone (II) and 2-acetylthiopenethio-semicarbazone (III) have been synthesized and characterized by employing different physicochemical and spectral (IR, NMR and Mass) methods. The spectral data are consistent with the structures proposed for the reagents. The reagents are found to be potential for the spectrophotometric determination of Hg(II), Ni(II), Cu(II), Co(II) and Zn(II). The author has developed spectrophotometric methods for the determination of toxic metal ions using APT, APS and ATT ligands in aqueous medium. The colour reactions are instantaneous and the methods do not involve heating of the reaction mixture. Derivative spectrophotometric techniques (both second and third order) are advantageously employed for the determination of Hg(II), Ni(II), Cu(II), Co(II) and Zn(II). Second or third order derivative spectrophotometry are employed for the simultaneous determination of Co(II) and Cu(II) using APS reagent, and Hg(II) and Zn(II) using APT reagent.