PH sensors with lithium lanthanum titanate sensitive material: applications in food industry

The use of the high lithium-conductive perovskite compound Li(3x)La(2/3-x)rectangle(1/3-2x)TiO(3) (LLTO) for the detection of ionic species in aqueous solution is investigated. A linear response in different pH-buffers is obtained with two configurations of the sensors. The membrane configuration proves the ability of this perovskite to detect the variation of pH between 2 and 10. The response is not Nernstian but the sensitivity and the response time are good. "all solid state" configuration is tested as pH sensor in various experiments. This sensor can be used in industrial processes like milk fermentation, in situ control of cleaning of fermentors (cleaning in place), yoghurt fabrication and waste water treatments for examples. The sensor is not sensitive to the variations of the redox potential of the solutions. A chemical stability of the ceramic at high temperature (up to 1000 degreesC) and high pressure and a good mechanical resistance make these ceramics valuable for the use as sensitive materials in industrial pH sensors. (C) 2003 Elsevier Science B.V. All rights reserved.