Using a typical shear cell arrangement, the degree of accuracy attained in the determination of the interdiffusion coefficients at low and moderate thermal and solutal Rayleigh numbers is analyzed here. It is concluded that, despite the marked directionality of these Fickian processes, thermal convective contamination is always negligible in real experiments but solutal convective contamination can be important even for moderate values of the solutal Rayleigh number. Nevertheless, in the range of values investigated and due to the above-mentioned directionality, the solutal convection could be minimized orienting the cell in such a way that its axis remains constantly aligned with the direction of the external disturbance. (C) 2010 Elsevier Ltd. All rights reserved.