Analytica Chimica Acta 509 (2004) 89–94 On-line preconcentration and simultaneous determination of heavy metal ions by inductively coupled plasma-atomic emission spectrometry Hassan Karami a , Mir Fazlollah Mousavi a,∗ , Yadollah Yamini a , Mojtaba Shamsipur b a Chemistry Department, Tarbiat Modarres University, P.O. Box 14115-111, Tehran, Iran b Chemistry Department, Razi University, Kermanshah, Iran Received 25 August 2003; received in revised form 10 November 2003; accepted 4 December 2003 Abstract A flow injection analysis system for on-line preconcentration and simultaneous determination of Bi 3+ , Cd 2+ , Co 2+ , Cu 2+ , Fe 3+ , Ni 2+ , Pb 2+ and Zn 2+ in aqueous samples by inductively coupled plasma (ICP)-atomic emission spectrometry with a charge coupled detector is described. The preconcentration of analytes is accomplished by retention of their chelates with sodium diethyldithiocarbamate in aqueous solution on a solid phase containing octadecyl silica in a minicolumn. Methanol, as eluent, is introduced into the conventional nebulizer of the ICP instrument. The effects of different parameters, including preconcentration flow rate (equal to sample flow rate (SR)), eluent flow rate (ER), weight of solid phase (W) and eluent loop volume (EV), were optimized by the super-modified simplex method. The optimum conditions were evaluated to be SR 7.2 ml min -1 , ER 3.5 ml min -1 , W of 100 mg and EV of 0.8 ml. An enrichment factor of 312.5 for each analyte was obtained. The detection limits of the proposed method for Bi 3+ , Cd 2+ , Co 2+ , Cu 2+ , Fe 3+ , Ni 2+ , Pb 2+ and Zn 2+ were evaluated as 1.3, 1.0, 0.8, 0.3, 14.7, 0.5, 5.5 and 0.1 ng l -1 , respectively. The effect of several metal ions on percent recovery was also studied. The method was applied to the recovery of these heavy metals from real matrices and to the simultaneous determination of these cations in different water samples. © 2004 Elsevier B.V. All rights reserved. Keywords: On-line preconcentration; Flow injection analysis; Dithiocarbamate; Heavy metal ions; Inductively coupled plasma-atomic emission spectrometry 1. Introduction During the past decade there has been a growing inter- est in the use of flow injection (FI) in electrochemical [1–3] and spectroscopic methods [4–7] for the determination of chemical species. Application of FI to inductively coupled plasma-atomic emission spectrometry (ICP-AES) for de- creasing the sample consumption and increasing sampling rate and measurement repeatability has also been reported [8–10]. Many methods have been developed for the preconcen- tration and separation of traces of metal ions from various samples, including those involving liquid–liquid extraction [11,12], co-precipitation [13], resin chelation [14], electro- chemical deposition [15] and solid phase extraction (SPE) ∗ Corresponding author. Fax: +98-21-8006544. E-mail address: mousavim@modares.ac.ir (M.F. Mousavi). [16]. Recently, SPE cartridges and disks have been widely and successfully used in on-line preconcentration processes [17,18]. They reduce solvent usage and exposure, disposal costs, and extraction time for sample preparation and obtain large enrichment factors. The use of ICP-AES for detection in FI systems for the determination of trace elements in real samples has several advantages such as an ability to simultaneously determine several trace metal ions, low detection limits and high re- peatability [19–22]. We have carried out widespread studies on the applica- tion of FI in electrochemical [23,24] and spectrometric de- termination [25–27] of different species. In continuation of our research work, we were also interested in the use of FI in ICP-AES determinations. In this work, we developed a new method for on-line preconcentration by chelation with sodium diethyldithiocarbamate (SDDTC) and simultaneous determination of trace amounts of the heavy metal ions Bi 3+ , Cd 2+ , Co 2+ , Cu 2+ , Fe 3+ , Ni 2+ , Pb 2+ and Zn 2+ by ICP-AES 0003-2670/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2003.12.022