Previous studies concerning the behaviour of n-type (100) GaAs in organic media have shown a dependence of the flatband potential V~b on the solution's redox potential [1,2]. Results obtained in CH3OH and CH3CN redox solutions indicated an almost complete Fermi level pinning (FLP) of the semiconductor. In these studies, pH effects were omitted, because CH3CN is an aprotic solvent and, in the case of CH3OH, very small pH variations were registered upon the addition of the different redox couples used. These variations, excluding two couples, did not exceed two pH units. As Vro shifts ranged over 0.7-0.8 V, the pH effect on the Vfb shift was considered to be negligible. To study the combined effect of a solution's redox potential and pH on the flatband potential displacement of an n-GaAs (100) surface, measurements were made in CH3OH solutions with different pH values. The pH of the solution was varied between 0.7 and 12 in methanol. The flatband potential was determined in different solutions before and after the addition of a given redox couple. These results are presented in the following communication.