in situ Carbonate/Bicarbonate/Carbon Dioxide Monitoring with Teflon® like Carbonate-Selective and pH SensorsUnited Science
Li Chen, Ph. D.
Introduction: A novel highly selective sensor for carbonate (CO32-) is described below. This sensor is based on Teflon®like matrixes and a new fluorophilic carbonate receptors. In conjugation with Teflon®like pH sensors, this sensor system can provide in situ monitoring of Carbonate (CO32-) /Bicarbonate (HCO3–) /Carbon Dioxide (CO2).
Background: A need for accurate and rapid determination of total carbon dioxide (i.e., carbon dioxide, bicarbonate and carbonate) arises from clinical chemistry, environmental analysis and industry. Polymeric membrane electrodes with trifluoroacetophenone derivatives as ionophores for carbonate were reported and have been applied for measurements in blood serum/plasma despite the low concentration of carbonate at physiological pH. Unfortunately, poor selectivities for CO32- over chloride and interference from salicylate limit their real-life applications. There has been no major improvement of selectivity since the 1990s.
Methods: Fluorophilic receptors and perfluorinated matrixes, with extremely low polarity and polarizability, were employed for this sensor. Benefiting from their noncoordinating and poorly solvating properties, the sensing membranes of these sensors are not only chemically very inert but also exhibit very high selectivities. The receptors exhibited enhanced selectivity for carbonate enhanced by several orders of magnitude as compared to existing sensors. In particular, the interference from chloride and salicylate was reduced by two and six orders of magnitude. The detection limit is below 10-5 M and covered the physiological range of CO32- concentration in the blood serum. Combined with pH value obtained by pH meters, concentration of CO32-, HCO3– and CO2can be determined simultaneously. This sensor system could be applied to analyze biological and environmental samples.
Reference: Chen, L. D., Mandal, D., Pozzi, G., Gladysz, J. A., Bühlmann, P. “Potentiometric Sensors Based on Fluorous Membranes Doped with Highly Selective Ionophores for Carbonate.” Journal of the American Chemistry Society, 2011, 133, 20869-20877.