The detection procedure consists of the measurement of the current as a function of the potential. This approach enhances the sensitivity and the detection selectivity due to the barrier effect to opposite-charged interferents. Clays are excellent ion exchangers and their ion exchange selectivity has been applied to the accumulation of charged electroactive analytes. Preconcentration applications at CLME are summarized in Table 2. Cationic exchanging clays are
essentially used for these analytical devices. The electroactivity of the adsorbed ions depends on the soaking time of the CLME in the analyte solution (accumulation time), on the nature and concentration of analyte, on the mode of preparation of the CLME, on the electrolyte nature, etc.