Journal of Environmental Management 88 (2008) 729–736 Development of a highly sensitive extractive spectrophotometric method for the determination of nickel(II) from environmental matrices using N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone C. Ramachandraiah, J. Rajesh Kumar, K. Janardhan Reddy, S. Lakshmi Narayana, A. Varada Reddy à Analytical Chemistry Division, Department of Chemistry, Sri Venkateswara University, Tirupati-517 502, Andhra Pradesh, India Received 23 March 2006; received in revised form 17 March 2007; accepted 25 March 2007 Available online 4 May 2007 Abstract Nickel(II) reacts with N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone (ECCT) and forms a yellow colored complex, which was extracted into n-butanol from sodium acetate and acetic acid buffer at pH 6.0. The absorbance value of the Ni(II)–ECCT complex was measured at different intervals of time at 400 nm, to ascertain the time stability of the complex. The extraction of the complex into the solvent was instantaneous and stable for more than 72 h. The system obeyed Beer’s law in the concentration range of 1.2–5.6 mg ml 1 of nickel(II), with an excellent linearity and a correlation coefficient of 0.999. The molar absorptivity and Sandell’s sensitivity of the extracted species were found to be 1.114  10 4 L mol 1 cm 1 and 5.29  10 3 mg cm 2 at 400 nm, respectively. Hence, a detailed study of the extraction of nickel(II) with ECCT has been undertaken with a view to developing a rapid and sensitive extractive spectrophotometric method for the determination of nickel(II) when present alone or in the presence of diverse ions which are usually associated with nickel(II) in environmental matrices like soil and industrial effluents. Various standard alloy samples (CM 247 LC, IN 718, BCS 233, 266, 253 and 251) have been tested for the determination of nickel for the purpose of validation of the present method. The results of the proposed method are comparable with those from atomic absorption spectrometry and were found to be in good agreement. r 2007 Elsevier Ltd. All rights reserved. Keywords: Nickel(II); Environmental matrices; Extractive spectrophotometry; N-ethyl-3-carbazolecarboxaldehyde-3-thiosemicarbazone 1. Introduction An important use of nickel in the food industry as a catalyst is evident from its use in the hydrogenation of oils. Nickel is an important element due to its high strength and resistance to corrosion in many media (Sharma, 1997). It is used in nickel plating and also in the manufacture of alloys along with iron, copper, aluminum, chromium, zinc and molybdenum. Nickel containing steels are highly resistant to corrosion. Because of its high melting point (1453 1C), nickel is also used in the production of heat-resistant steels and cast iron. Nickel-plated steels are used in the manufacture of some food processing vessels and many other pieces of equipment. Nickel(II) is present in small amounts in most soils, plants and animal tissues. The interest in the determination of nickel has grown con- siderably in recent years, owing to its involvement in some essential metabolic processes (Judith and Peter, 1998). Nickel is relatively non-toxic and does not cause any serious human health hazard, despite the fact that acid foods take up nickel during cooking. The nickel deposited in the human body from nickel vessels is not readily absorbed and causes no detectable hazard. However, a high incidence of respiratory tract neoplasia among work- ers in nickel refineries and carcinogenic properties of this metal have been reported (Sharma, 1997). Thio- and phenylthiosemicarbazones have a wide range of applications in medicine and agriculture. Owing to the ability of these reagents to form intense colored complexes ARTICLE IN PRESS www.elsevier.com/locate/jenvman 0301-4797/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2007.03.033 à Corresponding author. Tel.: +91 877 2232659; fax: +91 877 2246111. E-mail address: ammireddyv@yahoo.co.in (A. Varada Reddy).