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A spectroanalytical method for remediation of chromium species from contaminated water samples based on flow injection hyphenated to a flame atomic absorption spectrometer is proposed. Iminodiacetic acid (IDA) was used as the chelating agent, and the chromium–IDA complex was preconcentrated on the minicolumn filled with polytetrafluoroethylene (PTFE) beads. The chemical and flow variables were optimized. The effect of commonly occurring matrix ions on the recovery of the chromium species was also studied. For a preconcentration time of 120 s, preconcentration factors and detection limits achieved for Cr(III)/Cr(VI) were 68/59, 0.11/0.13 μg L-1, respectively. The relative standard deviation for 5 replicates of measurements for 100 μg L-1 level was 1.2/1.4% for Cr(III)/Cr(VI), respectively. Real water samples collected from industrial sites and the Yamuna river were analyzed and spike recovery tests were performed. The method validation was done by analyzing the chromium concentration in NIST SRM 1640a Trace Elements in Natural Water. centrations of the various chemical forms of an element that together make up the total concentration of that element in a given matrix (3). Spectrometric techniques are most commonly used for trace Cr determination (4). Flame atomic absorption spectrometry (FAAS) is a popular technique with considerable accuracy and precision. However, in practice for complex matrices, quantification is often very difficult due to the presence of interfering effects, comprised of spectroscopic and non-spectroscopic interferences. Moreover, in some cases, the concentration of the analyte might be too low to be directly analyzed. The most effective way to avoid these problems is to perform appropriate sample pretreatment aimed at improving the limits of detection (LODs) by removal of interferences as well as preconcentration of the analyte into a smaller sample volume, thus effectively increasing its concentration (5). In order to bring the analyte concentration into the detection range of the detector, a preconcentration step is required before the final measurement. Solid phase extraction (SPE) is an efficient separationpreconcentration technique for trace metal analysis (6) SPE offers the advantages of flexibility, is economical and, more importantly, is environmentally friendly. Despite these advantages, SPE can be timeconsuming, requires large sample or reagent volume, and the risk of contamination and loss of analyte during analysis is common (7). The combination of flow injection preconcentration using SPE with FAAS determination in an online method (FI-SPE-FAAS) has proven to be an effective system for trace element determination in various systems. It provides better sensitivity, effective removal of interfering ions, low cost, and offers high sampling rate (8). The various on-line systems proposed for the determination of chromium include polymeric support (9), alumina (10), biosorbents (11), and nanomaterials (12). In recent years, polymer-based systems have gained considerable attention in speciation INTRODUCTION Metal pollutants are non-biodegradable in nature. Thus, once they enter the environment, the toxicity caused by them mainly depends on the chemical form they exist in. Chromium is one of the common pollutants introduced into water sources as a result of various industrial processes. The toxicity of chromium depends on its oxidation state. Cr(III) is considered biologically essential to mammals as it is responsible for the glucose, lipid and protein metabolism. Cr(VI) ions are highly toxic because of their high oxidation potential and small size which allows them to penetrate through cell membranes and thus leads to the oxidation of bio-molecules (1). The toxic effects of Cr(VI) are chronic ulcers, dermatitis, lung and skin cancers. The World Health Organization (WHO) has decided the permissible limit for chromium in water to be 0.05 mg L-1 (2). The development in the industrial sector has amplified the problems associated with environmental pollution. Therefore, remediation of chromium species from industrial effluents has become extremely important. It is due to these two distinct effects that the precise and accurate determination of Cr(III) and Cr(VI), especially at ultra-trace levels, in environmental samples is urgently required. Speciation is defined as the determination of the individual conanalysis because of the advantages of hydro-phobic character, ease of surface modification, thermal stability, and high surface area (13-15). In the present study, polytetrafluoroethylene (PTFE) beads have been used as the solid phase extractant for the preconcentration of chromium species. PTFE beads possesses properties such as swelling and chemical inertness, low friction coefficient, etc., which makes them appropriate for solid phase extraction studies (16, 17). Iminodiacetic acid (IDA) was used as a chelating agent to complex both Cr(III) and Cr(VI) at a different pH. Studies have reported that IDA can be used as a complexing agent for both Cr(III) and Cr(VI) (18, 19). The optimized method was applied for chromium determination in industrial and river water samples, and spike recovery tests were carried out. The method was validated by analyzing standard reference material (SRM) NIST 1640a Trace Elements in Natural Water (National Institute of Science and Technolgy, Gaithersburg, MD, USA).

Chromium Speciation in Contaminated Water Samples Using PTFE Beads Packed Minicolumn and FI-FAAS Determination