An optical sensor for determination of low pH values based on covalent immobilization of Congo red on triacetyl cellulose films via epichlorohydrin

摘要

A new method for immobilization of some indicators with amino groups on triacetyl cellulose beds was applied for construction of an optical sensor for measurement of low pH values. Congo red was used as a pH indicator which was immobilized covalently on triacetyl cellulose via epichlorohydrin. The response of the optical sensor to pH of the solutions was found to be 0-4.5. The effect of influencing parameters on activation of the hydrolyzed film by epichlorohydrin and also on the reaction of the activated film with the indicator was studied and they were optimized. Under optimum experimental conditions, the obtained results showed that the constructed optical sensor has a good repeatability, reproducibility, short term and long term stability (more than 9 months) and a relatively short response time (about 150s) for a relatively wide pH range.