Electroanalysis at Salt – Cotton – Electrode Interfaces: Preconcentration Effects Lead to Nano‐Molar Hg 2+ Sensitivity

Cotton is employed as a sample absorbent which is analysed sandwiched between a glassy carbon electrode and ammonium nitrate salt in a humidified argon atmosphere (ca. 80 % relative humidity). Exploratory experiments show that well‐defined voltammetric responses for the Fe(CN) 6 3−/4− redox system pre‐absorbed into cotton are observed. Experiments with gold plating solution absorbed into cotton reveal the microscopic regions (cotton – glassy carbon contact points) of electrochemical activity where gold microparticles are plated onto the cotton surface. Stripping voltammetry experiments for trace metals such as Hg 2+ pre‐absorbed into cotton show a surprisingly high sensitivity with nanomolar detection readily achieved.