In this paper, we investigated Langmuir Blodgett films from various (M(n+)(C-)n)(TCNQC18)nx mixtures (where TCNQC is tetracyanoquinodimethane and C- is a water-soluble inorganic anion (Br-, I- or BF4-)). We observed a spontaneous reduction of TCNQC18 in the mixed films, whereas pure TCNQC18 films do not show any reduction of this species. A tentative explanation is given in terms of a redox potential scale shift at the air-water interface.