New approaches to polyaniline optical sensors: pH, acetic acid and amonia determination
- de Marcos, S
- Asensio, C
- Uruñuela, I
- Gallarta González, Félix
- Galban, J
- Castillo, JR
ISSN: 0212-0569
Año de publicación: 2000
Volumen: 19
Páginas: 99-104
Tipo: Artículo
Otras publicaciones en: Química analítica : The international journal of the Spanish Society for Analytical Chemistry
Resumen
Optical sensors based on polyaniline (PAn) for pH, volatile acetic acid and ammonia determination are presented. The main advantage of these sensors is that no indicator dye is needed because the polymer itself acts as both the matrix support and the indicator. Although PAn has already been used for pH optical sensor, the sensitivity of the optical sensor to this parameter has been improved by using a different oxidant (iron(III) chloride). The analytical applications of the PAn films have also been extended to volatile compounds dissolved in aqueous solution (acetic acid and ammonia). To this end PAn films were covered with a thin silicone film (1.32 x 10(-4) g cm(-2)), only permeable to gases, and therefore independent on the pH of the solution. These films have been characterised for reversible acetic acid determination and have a linear range from 0.02 to 0.6 M and an RSD of 1.9%. Their application to vinegar samples was in agreement with that obtained by the Official Method of Analysis. The procedure was also used for ammonia determination (linear range from 1.8 x 10(-3) to 1.8 x 10(-4) M); the sensor, however, did not exhibit reversibility.