The Clark method is commonly used in industrial production or scientific research to measure the concentration of dissolved oxygen in water or solutions. Because this method directly converts the analyte into an electrical signal, it offers a sensitive test response and facilitates continuous online analysis, making it widely applicable. Depending on the anode material and electrolyte used, the Clark method is further divided into electrochemical polarography and Gavanic thin-film current analysis.
In polarography, the cathode for determining dissolved oxygen in water is a gold or platinum electrode, and the anode is a silver electrode (Ag/AgCl reference electrode). The electrolyte is a KCl solution, and the DC power supply voltage is 0.65–0.85 V. When the anode material is changed to lead and the electrolyte to KOH solution, it becomes the Gavanic method. Compared to polarography, the Gavanic method provides faster readings due to the more rapid oxidation reaction of lead at the anode, and it does not require polarization. It is often used for general laboratory analysis, but frequent maintenance is necessary. Polarography, on the other hand, requires polarization before use but does not require frequent maintenance, making it particularly suitable for continuous online analysis.
