Mirzaei & Behzadi: Journal of aoaC international Vol. 96, no. 2, 2013 441 Received March 15, 2011. Accepted by AK April 21, 2011. Corresponding author’s e-mail: m_mirzaei@mail.uk.ac.ir DOI: 10.5740/jaoacint.11-105 RESIDUES AND TRACE ELEMENTS A simple and rapid dispersive liquid–liquid microextraction based on solidifcation of foating organic drop method prior to fame atomic absorption spectrometry was developed for preconcentration and determination of copper. In this technique, simultaneous complex formation and extraction was performed with rapid injection of a mixture containing ethanol, 1-undecanol, and 1-(2-pyridylazo)-2-naphthol into a water sample spiked with Cu(II). After centrifugation, the test tube was cooled in an ice bath, and solidifed extract transferred into a conical vial. Finally, it was dissolved into ethanol and copper concentration was determined. Some effective parameters of extraction and complex formation, such as extraction and disperser solvent type and volume, pH, concentration of the chelating agent, salt effect, and extraction time, were optimized. Under the optimum conditions, the calibration graph was linear in the range of 0.50 ng/mL to 0.30 µg/mL, with an LOD of 0.16 ng/mL. The RSD for 10 replicate measurements of 50.0 ng/mL of copper was ±1.4%. Two certifed reference materials were analyzed, and the determined values were in good agreement with the certifed values. W ith technological advancement, metal pollution is a great threat to human health, plants, and animals. Copper (Cu) is considered an essential micronutrient that is needed by plants and humans only at very low levels; it is toxic at high levels. Copper at nearly 40 ng/mL is required for normal metabolism of many living organisms (1, 2). The U.S. Environmental Protection Agency requires that levels of Cu in drinking water be less than 1.3 mg Cu/L (3). Thus, the development of new methods for selective separation, preconcentration, and determination of Cu(II) in different industrial, medicinal, and environmental samples is of continuing interest. Currently, the most common analytical methods for the copper trace determination are the fame atomic absorption spectrometry (FAAS; 4–6), electrothermal atomic absorption spectrometry (7–9), and inductively coupled plasma–optical emission spectrometry (ICP-OES; 10, 11). Because of low concentration of analytes and complex matrixes, sample preparation, such as extraction, cleanup, and preconcentration before instrumental analysis is essential. Liquid–liquid extraction (12, 13) and SPE (14–18) are two traditional pretreatment methods widely used for separation and preconcentration of metal ions from matrixes. Special attention is now focused on techniques characterized by a considerable reduction of organic solvents, which decreases environmental pollution greatly throughout the analytical procedure (19). Based on this premise, solid-phase microextraction (SPME) and four liquid-phase microextraction (LPME) methods have been reported. SPME is a solvent-free process developed by Arthur and Pawliszyn (20) that includes simultaneous extraction and preconcentration of analytes from aqueous samples or the headspace of the samples. However, SPME is expensive, the fber used is fragile and has a limited lifetime, and sample carryover can be a problem (21). Single- drop microextraction (SDME) is a preconcentration technique based on the use of a microdrop of extractant exposed to the sample solution or to the headspace above the sample when analytes are volatile or semivolatile headspace-SDME (22, 23). However, disadvantages of these methods are the fast stirring that may break up the organic solvent drop and possible air bubble formation (24). They are time-consuming and, in most cases, equilibrium is not attained even after a long period of time (25). In hollow fber LPME, the analyte is extracted from an aqueous sample into a water-immiscible extractant immobilized in the pores of a hollow fber (26, 27), typically made of polypropylene and supported by a microsyringe. However, this technique suffers from some drawbacks since the manipulation of the hollow fber at the time of placing it at the tip of the needle of the microsyringe before the microextraction process could be a source of contamination (27, 28). Dispersive liquid–liquid microextraction (DLLME), introduced by Rezaee et al. (29), is a simple and fast technique based on the cloudy solution formed when an appropriate mixture of an extractant with high density and a disperser solvent with high miscibility in both the extractant and aqueous phase is quickly injected into the aqueous sample. The fne droplets of extraction solvent are dispersed throughout the aqueous sample, allowing their interaction with the analyte. The surface area between extraction solvent and aqueous sample is very large, so an equilibrium state A Simple and Rapid Dispersive Liquid–Liquid Microextraction Based on Solidifcation of Floating Organic Drop Method Combined with Flame Atomic Absorption Spectrometry for Preconcentration and Determination of Copper MohaMMad Mirzaei Shahid Bahonar University of Kerman, Department of Chemistry, Kerman, Iran Mansoureh Behzadi Shahid Bahonar University of Kerman, Department of Chemistry, Kerman, Iran Shahid Bahonar University of Kerman Young Research Society, Kerman, Iran Downloaded from https://academic.oup.com/jaoac/article/96/2/441/5654947 by guest on 17 July 2022