Review Latest approaches on green chemistry preconcentration methods for trace metal determination in seawater e A review Noelia Soledad La Colla a, * , Claudia Elizabeth Domini b , Jorge Eduardo Marcovecchio a, c, d , Sandra Elizabeth Bott  e a, e a Instituto Argentino de Oceanografía (IADO e CONICET/UNS), Camino La Carrindanga km 7.5, 8000 Bahía Blanca, Argentina b Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1251, 8000 Bahía Blanca, Argentina c Universidad de la Fraternidad de Agrupaciones Santo Tom as de Aquino, Gasc on 3145, 7600 Mar del Plata, Argentina d Universidad Tecnol ogica Nacional e FRBB, 11 de Abril 445, 8000 Bahía Blanca, Argentina e Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, 8000 Bahía Blanca, Argentina article info Article history: Received 21 May 2014 Received in revised form 19 November 2014 Accepted 27 November 2014 Available online Keywords: Seawater Trace metals Preconcentration techniques Liquideliquid microextraction techniques abstract Evaluation of trace metal levels in seawater samples is undertaken regularly by research groups all over the world, leading to a growing demand for techniques involving fewer toxic reagents, less time- consuming protocols and lower limits of detection. This review focuses on providing a brief but concise description of the latest methodologies developed to this end, outlining the advantages and disadvantages of the various protocols, chelating and dispersive agents and instruments used. Conclu- sions are drawn on the basis of the articles reviewed, highlighting improvements introduced in order to enhance the performance of the protocols. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Monitoring the presence of trace metals in seawater matrices is of great importance since they interact with most marine fauna, particularly in estuaries -unique ecosystems with complex and dynamic processes of ecological and environmental significance- and because of their effect on human development along the coast. The determination of trace metals in seawater samples using conventional liquideliquid extractions (LLE) requires the use of large volumes of samples, which are usually difficult to obtain. The procedure usually involves considerable amounts of potentially toxic organic solvents to achieve an efficient extraction and is furthermore considered to be a tedious, multistage operation. The adequate disposal and treatment of the generated waste is also a time-consuming process, thus increasing the cost of the analysis. In addition, organic solvents can be deleterious to some analytical techniques (e.g. Hari Babu et al., 2007; Stalikas, 2002), calling for an alternative approach to sample treatment. Seawater samples are particularly difficult to study since the metal concentration within these solutions is usually quite low, often making it necessary to carry out preconcentration steps, and the saline matrix interferes with the determination. In order to overcome these difficulties it has been proposed that the traditional liquideliquid extraction principle be miniaturized, options of this nature being safer and more environmentally friendly since they diminish the use of organic solvents and acids. The lower cost and lower risk of sample contamination implied by these novel tech- niques is also to their advantage. Green chemistry principles aim at reducing hazardous impacts on human health and the environment. The techniques evaluated here are also designed to be less time-consuming, at the same time ensuring good recoveries and limits of detection. Although numerous reviews have discussed miniaturized pre- concentration techniques for trace metal determination or greener strategies for preconcentration, the present study is the first to focus on the applicability of these microextraction procedures exclusively to seawater samples. This article prioritizes strategies that minimize sample volume and avoid the use of toxic reagents * Corresponding author. Tel.: þ54 291 4861112. E-mail addresses: noelacolla@hotmail.com (N.S. La Colla), dominiclaudia@ hotmail.com (C.E. Domini), jorgemar@criba.edu.ar (J.E. Marcovecchio), sbotte@ criba.edu.ar (S.E. Bott e). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman http://dx.doi.org/10.1016/j.jenvman.2014.11.030 0301-4797/© 2014 Elsevier Ltd. All rights reserved. Journal of Environmental Management 151 (2015) 44e55