Derivatised l-methionine: a new amino polycarboxylate functionality for trace level speciation of chromium by solid-phase extraction

Abstract

Chemical speciation and separation of inorganic chromium species in environmental samples were performed using a newly synthesised chelating ligand, N,N-(Bis-acetato) l-methionine. The ligand can bind very efficiently with Cr(III) and Cr(VI) at two different pH. The ligand loaded on alumina can be reused several times without any significant loss of the ligating group. The maximum adsorption capacity for Cr(III) at any pH above 4.0 is 0.5663 mmol g⁻¹ and for Cr(VI) at pH 2.0 is 1.23 mmol g⁻¹. About 3.0 mol L⁻¹ HCl can completely desorb both chromium species from the polymeric matrix. The detection limit (three times the standard deviation of the blank, as obtained from flame atomic absorption spectroscopic (FAAS) method) for Cr(III) and Cr(VI) were found to be 45 and 46 ng mL⁻¹, respectively. The sorption of both Cr(III) and Cr(VI) was found to follow a second-order rate law. The developed method is used for the chemical speciation and removal of chromium species from different environmental samples and validated by comparing with some standard samples as well as by comparing with results using previously developed method. The concentration of chromium was monitored using FAAS.

Keywords:

• Chromium
• Speciation
• Chelating resin
• L-methionine
• FAAS

Acknowledgments

Financial assistance from UGC-DAE-Kolkata centre is gratefully acknowledged. Authors thank Sudipta Das, Subarna Guha, Animesh Sahana, Arnab Banerjee, Sisir Lohar and Debasis Karak for their assistance.