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Adsorptive Transfer Chronopotentiometric Stripping of Sulfated Polysaccharides Applied to Seawater Analysis

Anomalous accumulation of organic matter in a form of macroaggregates (mucilages) under specific climatic and trophic conditions was documented in the Adriatic sea [1]. The macroaggregates of the northern Adriatic are mostly composed of water-soluble heteropolysaccharides and longer polymethylene chains attached to the monosaccharide units, suggesting that polysaccharides in Adriatic macroaggregates originate primarily from phytoplankton exudates and structural polysaccharides [2]. Abiotically formed transparent exopolymeric particles (TEP) [3] are composed mostly of acidic polysaccharides and have an important role in biogeochemical cycling of trace elements in the seawater. The method of analysis for the polysaccharides in seawater is not straightforward [3] and that is why we tried to develop and to apply electrochemical method of analysis. Recently, by applying chronopotentiometric stripping (CPS), it was proven, that if sulphate groups are attached to a PS chain two catalytic peaks H named peak H'PS and peak HPS, in buffered solution appear [4]. Both peaks are a result of catalytic hydrogen evolution on mercury electrode. They strongly depend on a buffer concentration which is directly coupled with catalyst regeneration [5]. In situ obtained peak HPS may enable a selective detection of nmol concentrations of sulphated polysaccharides (S-PS) [4]. Further work was done to obtain the catalytic effect of S-PS placed in seawater (pH 8.2), where direct stripping did not give catalytic peaks. Adsorptive transfer chronopotentiometric stripping (AdT CPS) procedure was applied in order to transfer accumulated S-PS from seawater to electrolyte suitable for its stripping. According to CPS of S-PS ι-carrageenan [4], acetate buffered sodium chloride solution (0.55 M) of pH 5.1 was the stripping electrolyte. Results show that AdTS enables the analysis of S-PS in seawater in pmol range [6]. References: [1] R.A. Vollenweider, A. Rinaldi, (eds) Marine Mucilages, Sci.Total Environ.165 (1995) pp. 1-235. [2] N. Kovač, P. Mozetić, J. Trichet, C. Defarge, Mar. Biol.147 (2005) 261. [3] U. Passow, Prog. Oceanogr. 55 (2002) 287. [4] S. Strmečki, M. Plavšić, B. Ćosović, V. Ostatna, E. Paleček, Electrochem. Commun. 11 (2009) 2032. [5] M. Heyrovsky, Electroanalysis 16 (2004) 1067. [6] S.Strmečki, M. Plavšić, Electrochem.Commun. in press

polysaccharides; constant current chronopotentiometry; seawater

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