An electrochemical technique is employed for measuring local, instantaneous liquid-solid mass transfer coefficients in downward cocurrent gas-liquid flow through a packed bed under pulsing flow conditions. The technique involves specially designed electrodes of the same dimensions as the packing material. Also microelectrodes on the surface of a particle are tested for flow diagnostics in the microscale. The feasibility of the method is examined. Interpretation of measurements from various electrodes provides information on the pattern of mass transfer and liquid distribution in the packing.