Abstract
A flow injection preconcentration system for the flame atomic absorption spectrometric determination of hexavalent chromium has been developed. The method employs on-line preconcentration of Cr(VI) on a minicolumn packed with Cr(VI)-imprinted poly(4-vinyl pyridineco-2-hydroxyethyl methacrylate) placed into a flow injection system. Hexava-lent chromium was eluted with a small volume of diluted hydrochloric acid into the nebulizer-burner system of a flame atomic absorption spectrometer. An enrichment factor of 550 and a 3σ detection limit of 0.04 μg·L-1 along a sampling frequency of 4 h-1 at a sample flow rate of 3.5 mL·min-1. The relative standard deviation is 2.9% for 1 μg·L-1 Cr(VI) (n = 11). The flow injection system proposed has the advantage of being simpler because the use of expensive and sophisticated instruments is avoided. Ease of use, continuous process and selectivity make this method suitable for Cr(VI) determination in different environmental samples such as sea and river waters, soils and sediments.
Highlights
Chromium exists in small quantities throughout the environment
Molecular imprinted (MIPs) or ion-imprinted polymers (IIPs) have been recognized as suitable materials and they are increasingly used in trace analysis because they are suitable for applications where analyte selectivity is essential
To optimize the Flow injection (FI) system for Cr(VI) determination, the main efforts were focused on the conditions for sample loading and Cr(VI) elution from the minicolumn, as well as the analytical FI-Flame atomic absorption spectrometry (FAAS) system which was coupled on-line with the preconcentration/separation unit in order to obtain highly sensitive, accurate and reproducible results
Summary
Chromium exists in small quantities throughout the environment. Chromite ore (FeCr2O4) is the most important commercial ore and is usually associated with ultramafic and serpentine rocks. In order to increase its sensitivity, achieve the separation of both chromium species and isolate the analyte from interfering matrix constituents were proposed several methodologies including solid phase extraction methods involving anion exchange resins [5,6], adsorption of Cr(VI) complexes with dithiocarbamate, or diphenylcarbazide on solids sorbents as macroporous polystyrene-divinylbenzene, Amberlite XDA, C18 bonded silica or activated alumina and chelating resins to determine by difference between total Cr and Cr(III) the Cr(VI) concentration [7,8,9,10,11,12,13,14]. Between IIPs, mainly were synthesized cationic materials to be selective to trace
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