Uso de membranas de Nafion para a construção de sensores ópticos para medidas de pH

Silvia Cristina Lopes Pinheiro, Ivo M. Raimundo Jr
2005 Química Nova  
bromothymol blue (BB) and methyl violet (MV), were studied aiming at constructing an optical sensor for pH measurement. BB revealed to be inadequate for developing sensing phases due to the electrostatic repulsion between negative groups of their molecules and the negative charge of the sulfonate group of the Nafion ® , which causes leaching of the dye from the membrane. On the other hand, MV showed to be suitable due to the presence of positive groups in its structure. The membrane prepared
more » ... embrane prepared from a methanolic solution whose Nafion ® /dye molar ratio was 20 presented the best analytical properties, changing its color from green to violet in the pH range from 0.6 to 3.0. The membrane can be prepared with good reproducibility, presenting durability of ca. 6 months and response time of 22 s, making possible its use for pH determination in flow analysis systems.
doi:10.1590/s0100-40422005000500036 fatcat:d3vfz2lzvrds5esxlrhby7ljyi