Tu ¨lin C ¸ etin Ahmet U ¨ lgen S ¸ erife Tokalıog ˘ lu Department of Chemistry, Faculty of Science, Erciyes University, Kayseri, Turkey Research Article On-line Solid Phase Extraction of Copper in Water Samples with Flow Injection Flame Atomic Absorption Spectrometry An on-line solid phase extraction method for the preconcentration and determination of Cu(II) by flame atomic absorption spectrometry has been described. The procedure is based on the retention of Cu(II) ions at pH 6.0 on a minicolumn packed with Amberlite XAD-1180 resin impregnated with chrome azurol S. After preconcentration, Cu(II) ions adsorbed on the impregnated resin were eluted by 1 mol L 1 HNO 3 solution. Several parameters, such as pH, type of eluent, flow rates of sample and eluent solutions, amount of resin were evaluated. At optimized conditions, for 3.5 min of preconcentra- tion time, the system achieved a detection limit of 1.0 mgL 1 , and a relative standard deviation of 1.2% at 0.2 mg mL 1 copper. An enrichment factor of 56-fold was obtained with respect to the copper determination. The proposed method was successfully validated by the analysis of standard reference material (TMDA 54.4 lake water) and recovery studies. The method was applied to the preconcentration of Cu(II) in natural water samples. Keywords: Chrome azurol S; Copper; Flame atomic absorption spectrometry; On-line preconcentration Received: July 4, 2010; revised: September 4, 2010; accepted: September 22, 2010 DOI: 10.1002/clen.201000264 1 Introduction The trace heavy metal determination is an analysis often asked to analytical chemists. The metal ions are among the main sources of pollution in the environment, since they have a significant effect on its ecological quality [1, 2]. Copper is an essential micronutrient. This element is needed by plants and animals at very low concentration and is toxic at higher levels [3]. Flow injection (FI) on-line separation and preconcentration tech- niques have shown great promise and become one of the most active research fields in automated solution analysis in recent years. FI on- line preconcentration and separation coupled with flame atomic absorption spectrometry (FAAS) have been shown to be powerful for determination of trace elements in a variety of matrices in view of the enhanced sensitivity, the efficient removal of matrix, high sample throughput, low consumption of sample and reagent, mini- mum risk of contamination and the low cost of the FAAS equipment. Most FI preconcentration methods are based on the use of a mini- column containing a chelating resin or a solid sorbent, which can significantly reduce sample volume [4–6]. The nature and properties of the packing materials are of prime importance for effective retention of analyte, while some basic requirements for them should be met, like fast and quantitative adsorption, effective elution, negligible swelling and shrinking, regeneration ability, high capacity, accessibility and high chemical resistibility [7]. Among the stationary phases usually used in FI-on- line solid phase extraction (SPE) for preconcentration of heavy metals, we can found C 18 [8], ion exchange resins [9, 10], modified silica gel [11], activated carbon [12, 13], Amberlite XAD-2 [1, 14], XAD-4 [15, 16], polyurethane foam [17], polytetrafluoroethylene turnings [18], knotted reactor [19], chitosan [20], synthetic zeolites [21], chro- mosorb 102 [22], surfactant coated alumina [3], cotton [23], and bamboo charcoal [24]. Chrome azurol S (CAS) is an organic colorimetric reagent which has some desirable characteristics such as high complex formation constant with metal ions, and high molar absorptivities and selec- tivity of the complex formations with metal ions. CAS provides the basis for sensitive methods for the determination of various elements. The complex formation of copper(II) with CAS had been studied by spectrophotometric and potentiometric methods [25, 26]. In the pH range of 5–7, two complexes with the composition Cu(H 2 O) 2 HCAS  and (Cu(H 2 O) 2 ) 2 CAS were detected: the stability con- stants were calculated to be log K ¼ 4.02  0.05 and log K ¼ 13.7  0.1, respectively (at 258C and ionic strength 0.1(KCl)) [26]. In the present work, a new on-line column separation/preconcen- tration method for FAAS determination of copper(II) ions in water samples using Amberlite XAD-1180 loaded with CAS is proposed. As far as we know there are no data about on-line Cu determination by using this chelating resin. The analytical parameters such as pH, type and concentration of elution solution, sample loading and elution flow rate, preconcentration time and also the effect of potential interferents in water samples were studied. Correspondence: Prof. Dr. S ¸erife Tokalıog ˘lu, Department of Chemistry, Faculty of Science, Erciyes University, 38039, Kayseri, Turkey E-mail: serifet@erciyes.edu.tr Abbreviation: CAS, Chrome azurol S; FAAS, flame atomic absorption spectrometry; FI, flow injection; PP, peristaltic pump; SPE, solid phase extraction. 244 Clean – Soil, Air, Water 2011, 39 (3), 244–249 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com