Preparation of a novel green optical pH sensor based on immobilization of red grape extract on bioorganic agarose membrane

The development of a novel green optical pH sensor for a wide range pH values is described based on the immobilization of grape extract on an optically transparent agarose biopolymer. Siahe Sardasht grape is a famous variety of grape in Iran that is used for red grape juice concentrate. The anthocyanins of Siahe Sardasht grape were extracted and used as a suitable dye for the preparation of a pH optical sensor, by its immobilization on a transparent agarose film. In an optimized coupling, pH of 10 and a dye concentration of 100 mg L-1, a sensitive sensor with long term stability was obtained. The sensor responds rapidly to the pH changes in a range of 1-10 with a response time of 3.0 min and repeatability better than 0.3% (RSD). The sensor was mounted in the quartz cells and successfully applied for pH monitoring. No evidence of leaching of the dye or any signal drift was observed. (C) 2015 Elsevier B.V. All rights reserved.