Rf. Rocha et al., FACTORIAL DESIGN OPTIMIZATION OF REDOX PROPERTIES OF METHYLENE-BLUE ADSORBED ON A MODIFIED SILICA-GEL SURFACE, Journal of electroanalytical chemistry [1992], 433(1-2), 1997, pp. 73-76
Methylene blue immobilized on silica surfaces modified with titanium d
ioxide and titanium phosphate were used in carbon paste mixtures to pr
epare electrodes. The electrochemical properties of methylene blue wer
e investigated by cyclic voltammetry. The electron mediator property o
f the dye was optimized using a factorial design, consisting of two le
vels and three factors. The factorial analysis was carried out by sear
ching for better reversibility of the redox process, i.e. the lowest s
eparation between anodic and cathodic peak potentials and a current ra
tio near unity. The supporting electrolyte concentration has a small e
ffect. The interaction between pH and the silica support was very sign
ificant for the peak separation. The solution pH has a significant eff
ect on the current ratio. Lower values for peak separation were observ
ed at pH 4.0 for STM and pH 7.0 for STPM. However, the current ratio w
as closer to unity for pH 4.0 in both cases. (C) 1997 Elsevier Science
S.A.