Author's personal copy Talanta 77 (2009) 1160–1164 Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Flow injection wetting-film extraction system for flame atomic absorption spectrometric determination of cadmium in environmental waters Ibrahim S.I. Adam, Aristidis N. Anthemidis ∗ Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University, Thessaloniki 54124, Greece article info Article history: Received 28 May 2008 Received in revised form 8 August 2008 Accepted 20 August 2008 Available online 28 August 2008 Keywords: Wetting film extraction Flow injection Solvent extraction Atomic spectrometry Cadmium abstract A newly simple flow injection wetting-film extraction system coupled to flame atomic absorption spec- trometry (FAAS) has been developed for trace amount of cadmium determination. The sample was mixed on-line with sodium diethyl dithiocarbamate and the produced non-charged Cd(II)–diethyl dithiocarba- mate (DDTC) chelate complex was extracted on the thin film of diisobutyl ketone (DIBK) on the inner wall of the PTFE extraction coil. The wetting-film with the extracted analyte was then eluted by a segment of the cover solvent, and transported directly to the FAAS for evaluation. All the important chemical and flow parameters were optimized. Under the optimized conditions an enhancement factor of 35, a sample frequency of 22 h -1 and a detection limit of c L = 0.7 gl -1 Cd(II) were obtained for 60 s preconcentration time. The calibration curve was linear over the concentration range 1.5–45.0 gl -1 Cd(II) and the relative standard deviation, R.S.D. (n = 10) was 3.9%, at 10.0 gl -1 concentration level. The developed method was successfully applied to cadmium determination in a variety of environmental water samples as well as waste-water sample. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The environment is continuously contaminated with large amount of toxic elements as consequence of human activities. Exposure to these toxic pollutants imposes not only risks to human health, but also potentially unacceptable ecological risks to plants, animals and microorganisms [1]. As the result, years of effort have been devoted to the development of more effective, fast, precise and accurate approaches for the determination of different elements like cadmium, in various environmental matrices using numerous analytical methods. The adverse effects of cadmium are the result not only of its high toxicity even at trace concentrations, but also of its bioaccumulation processes along the food chain and into vital human organs like kidney. Flame atomic absorption spectrometry (FAAS) is among the most widely used techniques for determination of heavy metals, however, its sensitivity is usually insufficient for monitoring the low level concentrations of these metals in environmental sam- ples. In addition, the interfering effect of the matrix components of complicated samples like sea-water, many times is a serious problem in the determinations by atomic spectrometry (AS). Con- sequently, a preconcentration and/or separation process is usually ∗ Corresponding author. Tel.: +30 2310997826; fax: +30 2310997719. E-mail address: anthemid@chem.auth.gr (A.N. Anthemidis). required prior the measurement. Although, liquid–liquid extrac- tion (LLE) has proven to be a reliable and efficient separation and/or preconcentration technique for metal determination, it is time and reagent consuming, as well as tedious and laborious procedure and hence, potentially prone to contamination of sample and environ- ment, when it is performed in batch (off-line) mode. However, the marriage of LLE with flow injection (FI) [2,3] offers a great ease to the analysis eliminating to a great extent, many of the drawbacks encountered in the batch mode. In classical FI–LLE systems, the on-line extraction process is accomplished by three major operations: (i) segmentation, (ii) extraction and (iii) separation [4]. The extraction efficiency into the narrow tube of the extraction coil is usually high and it is completed in a few seconds. These parameters are attributed to the formation of a very thin film of one phase on the inner wall of the extraction coil, surrounding the segments of the other phase. The material of the coil (hydrophobic or hydrophilic) defines which phase will form the wetting-film according to the polarity of the solvent [5]. However, FI–LLE has not been widely accepted for routine anal- ysis, due to the critical instrumentations, segmentor and phase separator, which affect significantly the reproducibility, stability and robustness of the method. Their design construction and oper- ation performance have been studied in detail [6–8]. On the other hand, several efforts have been made to eliminate the need for segmentation and phase separation. 0039-9140/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2008.08.015