Chitosan membranes as sorbents for trace elements determination in surface waters

Abstract

Chitosan membranes (non-crosslinked, crosslinked, and modified with L-cysteine) were evaluated as sorbents prior to electrothermal atomic absorption spectrometry (ETAAS) determination of total dissolved metal content in surface water samples. Different types of chitosan membranes were prepared in the presence or absence of L-cysteine. Chemical parameters for quantitative sorption/desorption of trace analytes have been optimized. The optimal pH for Cd(II), Cu(II), Ni(II), and Pb(II) sorption using L-cysteine-modified membrane is between 7 and 8.5 and coincides with typical surface water pH, allowing in situ preconcentration of analytes without any additional water sample pretreatments. Non-crosslinked chitosan membrane could be used for simultaneous sampling, transportation, and laboratory determination of Hg(II). Determination limits (calculated as 10σ) achieved for total dissolved metal contents are: Cd 0.001 μg/L, Cu 0.02 μg/L, Ni and Pb 0.05 μg/L, and relative standard deviations were 10-15% for all elements at concentration level of 0.05-2 μg/L. The determination limit achieved for Hg(II) was 0.012 μg/L and relative standard deviations at concentration levels 0.015-2 μg/L were within 9% and 15%. Non-crosslinked chitosan membrane was proposed as an efficient sorbent for Hg(II) preconcentration and determination in river and lake waters; L: -cysteine modified chitosan membrane was recommended for solid phase extraction of Cd(II), Cu(II), Ni(II), and Pb(II) from surface (lake, river, and sea) waters. The application of chitosan membranes as adsorbents for in situ field preconcentration of the analytes and their subsequent determination by CVAAS and ETAAS in water samples has been demonstrated.