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Eco-friendly Approach for a Facile Synthesis of o-Hydroxyphenylthiourea and its Property as an Analytical Reagent in Sensing Mercury (II)

Author Affiliations

  • 1Dept. of Chem., Sri Sathya Sai Inst. of Higher Learning (Deemed to be University), Prasanthi Nilayam, Puttaparthi, Anantapur, INDIA

Res.J.chem.sci., Volume 2, Issue (3), Pages 30-40, March,18 (2012)


An efficient, eco-friendly synthesis of o-Hydroxyphenylthiourea(OHPTU) using microwave and ultrasound assisted methods are described. Green reaction conditions, uniform heating, short reaction time, high yield, high efficiency and convenient work up conditions are advantages of these methods. These merits are in congruence with the green chemistry requirements of energy saving, environmental safety aspects and using nonclassical energy forms. OHPTU undergoes auto-oxidation to form an yellow coloured disulphide, 1,1’-dithio-bis-N-(o-Hydroxyphenyl) formamide. The reaction is very slow and rate of formation of the coloured dimer increases with concentration of mercury(II) ions. Photometric and fluorometric methods were employed to study this reaction at pH 5.0 and the range of determination was determined to be 800nM–15nM using fixed time method. The absorbance measurements were taken at λmax=416nm and the quenching effect of mercury(II) on the fluorescence intensity of OHPTU was studied at λEm=520nm using Stern-Volmer plots. Effects of variation in pH, temperature, reagent concentration; role of activators and surfactants; and interference of associated metal ions in the catalysed oxidation of OHPTU are reported. This method is cost effective, fairly selective, sensitive and there is no need for any pre-concentration procedure. The developed method was successfully applied to the determination of mercury(II) present in stream water, ground water, fountain water, tap water and sludge water samples.


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