Analytical Sciences

Chemical Speciation of Chromium(III) and (VI) Using Phosphonium Cation Impregnated Polyurethane Foams Prior to Their Spectrometric Determination

M. S. EL-SHAHAWI, A. S. BASHAMMAKH, and M. ABDELMAGEED

Department of Chemistry, Faculty of Science, King Abdulaziz University, P. O. Box 80203, Jeddah 21589, Saudi Arabia

Fast and selective sorptions of Cr(VI) species from aqueous media onto tetraphenylphosphonium bromide (TPP⁺ · Br⁻) physically immobilized polyurethane foams (PUFs) sorbent were achieved. Based on the Scatchard model of binding sites of the PUFs and Langmuir and Dubinin–Radushkevich (D–R) adsorption models of Cr(VI) retention onto TPP⁺ · Br⁻ immobilized PUFs, a dual retention mechanism involving absorption related to “weak-base anion ion exchange” and an added component for “surface adsorption” was proposed. Thus, the TPP⁺ · Br⁻ loaded PUFs were successfully packed in column mode for preconcentration of trace and ultra trace concentrations of Cr(VI) as halochromates [CrO₃C]⁻_aq from aqueous HCl media. The retained [CrOCl₃]⁻_aq species were recovered with NaOH (1.0 mol L⁻¹) and analyzed by flame atomic absorption spectrometry. Cr(III) species after oxidation to Cr(VI) with H₂O₂ in aqueous KOH (1.0 mol L⁻¹) were also retained and could be recovered by the proposed method. The limits of detection (LOD) and quantification (LOQ) of Cr(VI) were 0.04 and 0.13 μg L⁻¹, respectively. The chemical speciation of Cr(III, VI) species in various water samples at trace and ultra trace levels were carried out by TPP⁺ · Br⁻ loaded PUFs packed column. The enhancement factor and sensitivity factor of [CrO₃C]⁻_aq sorption were 80.0 and 30.0, respectively.

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