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Abstract
Chitin is an effective sorbent which can be used in environmental monitoring, beyond obvious applications in withholding metal-containing pollutants from wastewater- or nuclear fuel reprocessing flows, since background levels in (purified) chitin are very low except for a few metals (Fe, Cu, Al, Ti, and Zn). Since retention of Mx+ and their complexes on chitin depend on an oxidation state, and to a lesser extent the presence of possible ligands or co-ligands, partition between chitin samples exposed to sediment and those exposed to water can be changed by environmental factors such as local biota producing or absorbing/metabolizing effective ligands such as citrate or oxalate and by changes of redox potential. Thermodynamics are studied via log P, using calibration functions log P vs. 1/r or log P vs. Σσ (sum of Hammett parameters of ligand donor groups) for di- and trivalent elements not involved in biochemical activity (not even indirectly) and thus measuring “deviations” from expected values. These “deviations” can be due to input as a pollutant, biochemical use of certain elements, precipitation or (bio-induced reduction of SO42− or CO2) dissolution of solids in sediment. Biochemical processes which occur deep in sediment can be detected due to this effect. Data from grafted chitin (saturation within ≤ 10 min) and from outer surfaces of arthropods caught at the same site do agree well. Log P is more telling than total amounts retrieved. Future applications of these features of chitin are outlined.
Highlights
Chitin is difficult to oxidize both by an anode and by chemical agents such as the common agents for saccharide analytic cleavage; chitin itself is completely silent in electrochemical experiments even though it does contain trace amounts of redox-active ions (Fe, Ti, Cu)
The chitin chitin sample sample can can be be located located in in either either sediment sediment or or open open water water
There are some difficulties: the reduction signal of Yb3+/2+ [48] in DMF does match that of the polysaccharide protons of chitin in same solvent at −1.5 V whereas Ce gives poorly reproducible data on adsorption unless the redox state is tightly controlled
Summary
Chitin is difficult to oxidize both by an anode and by chemical agents such as the common agents for saccharide analytic cleavage; chitin itself is completely silent in electrochemical experiments (when dissolved by adding Li salts in dimethyl formamide) even though it does contain trace amounts of redox-active ions (Fe, Ti, Cu). It can be oxidized by certain staining agents such as Ag+ or OsO4 only after deacetylation [6] while not being attacked by common reagents used in saccharide cleavage and analysis, such as Polysaccharides 2021, 2, 773–794.
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