Improved Metal Cation Optosensing Membranes through the Incorporation of Sulphated Polysaccharides
P. R. M. Santos,
A. Johny,
C. Q. Silva,
M. A. Azenha,
J. A. Vázquez,
J. Valcarcel,
C. M. Pereira,
A. F. Silva
Affiliations
P. R. M. Santos
Research Center in Chemistry UP (CIQUP), Institute of Molecular Sciences (IMS); Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
A. Johny
Research Center in Chemistry UP (CIQUP), Institute of Molecular Sciences (IMS); Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
C. Q. Silva
Research Center in Chemistry UP (CIQUP), Institute of Molecular Sciences (IMS); Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
M. A. Azenha
Research Center in Chemistry UP (CIQUP), Institute of Molecular Sciences (IMS); Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
J. A. Vázquez
Grupo de Reciclado y Valorización de Materiales Residuales (REVAL), Instituto de Investigaciones Marinas (IIM-CSIC), C/Eduardo Cabello, 6, 36208 Vigo, Spain
J. Valcarcel
Grupo de Reciclado y Valorización de Materiales Residuales (REVAL), Instituto de Investigaciones Marinas (IIM-CSIC), C/Eduardo Cabello, 6, 36208 Vigo, Spain
C. M. Pereira
Research Center in Chemistry UP (CIQUP), Institute of Molecular Sciences (IMS); Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
A. F. Silva
Research Center in Chemistry UP (CIQUP), Institute of Molecular Sciences (IMS); Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
Optosensing chitosan-based membranes have been applied for the detection of heavy metals, especially in drinking water. The novelty of this study is based on the use of sulphated polysaccharides, in such optosensing membranes, aiming at an improved analytical performance. The sulphated polysaccharides, such as ulvan, fucoidan and chondroitin sulfate, were extracted from by-products and wastes of marine-related activities. The membranes were developed for the analysis of aluminum. The variation in the visible absorbance of the sensor membranes after the contact between the chromophore and the aluminum cation was studied. The membranes containing sulphated polysaccharides showed improved signals when compared to the chitosan-only membrane. As for the detection limits for the membranes containing ulvan, fucoidan and chondroitin sulfate, 0.17 mg L−1, 0.21 mg L−1 and 0.36 mg L−1 were obtained, respectively. The values were much lower than that obtained for the chitosan-only membrane, 0.52 mg L−1, which shows the improvement obtained from the sulphated polysaccharides. The results were obtained with the presence of CTAB in analysis solution, which forms a ternary complex with the aluminum cation and the chromophore. This resulted in an hyperchromic and batochromic shift in the absorption band. When in the presence of this surfactant, the membranes showed lower detection limits and higher selectivity.
