Electrochemistry of chitosan amino-glycan and BSA protein mixture under seawater conditions

We investigated the electrochemical properties of the models chitosan oligosaccharide (CHOS), an amino-glycan, and BSA protein, as major components of N-bearing polymeric organic material (N-POM) in seawater. The chronopotentiometric stripping method (CPS) and a hanging mercury drop working electrode (HMDE) were used to detect catalytic peaks (Ep around -1.8 V/-1.9 V vs. Ag/AgCl (3M KCl)) generated by the catalytic hydrogen evolution reaction (CHER). "Peak HOS" of CHOS was not observed under seawater conditions (pH 8.2). Since both analytes measured separately produced catalytic peaks in CPS after their adsorptive transfer (AdT) from seawater into slightly acidic and neutral buffers (pH-s 5.3-7.1), we investigated measurement conditions that might allow selective AdT detection of CHOS in the CHOS + BSA seawater mixture. Only one catalytic peak was observed in the AdT CPS of mixture, which was attributed to the involvement of both compounds in adsorption on HMDE and consequently in CHER. The height and Ep of this peak tended to correspond to the analyte with the higher concentration in the mixture. Regardless of the choice of pH or buffer, the combination of CPS measurement conditions or the rinsing mode by relevant solvents and solutions during AdT, BSA was not efficiently removed from the HMDE and selective detection of CHOS in the mixture was not achieved. These results will be applicable in the electrochemical analysis of amino-glycans in natural seawater samples containing a mixture of N-POM, but also represent an investigation of the basic electrochemical properties of CHOS and BSA.