Dissolved oxygen (DO) probes are widely used in various industries and applications to measure the concentration of oxygen in liquids such as water, wastewater, and other aqueous solutions. The probes use a variety of technologies to determine the amount of oxygen present, including optical, electrochemical, and polarographic methods. In electrochemical probes, an electrolyte is an essential component that enables the flow of electrical current between the probe and the solution being measured.
The electrolyte in a dissolved oxygen probe serves several important functions. First and foremost, it provides a pathway for the transfer of electrons between the oxygen in the sample solution and the probe’s electrode. This transfer is necessary to generate an electrical current that can be measured and converted into a reading of the oxygen concentration. The electrolyte also helps to maintain the stability and accuracy of the probe’s measurements by preventing interference from other substances that may be present in the sample solution.
The most common electrolyte used in dissolved oxygen probes is potassium chloride (KCl) solution. This solution is typically mixed with a gel-like substance, such as polyethylene glycol (PEG), to create a thick, viscous paste that adheres to the electrode and prevents the electrolyte from leaking out. The KCl solution provides the necessary ions to facilitate the flow of electrons between the sample solution and the probe’s electrode. The K+ ions from the KCl solution react with the O2 molecules in the sample solution at the cathode, while the Cl- ions react at the anode. This reaction generates an electrical current that is proportional to the concentration of oxygen in the sample.
Another type of electrolyte that can be used in dissolved oxygen probes is sodium sulfite (Na2SO3) solution. This electrolyte is less commonly used than KCl but is sometimes preferred in certain applications, such as in wastewater treatment plants where high levels of chloride ions can interfere with the measurements. Sodium sulfite acts as a reducing agent that helps to remove any dissolved oxygen from the electrolyte solution itself, which can improve the accuracy and stability of the probe’s readings.
In addition to KCl and sodium sulfite, there are other types of electrolytes that can be used in dissolved oxygen probes. For example, lithium chloride (LiCl) solution is sometimes used in specialized applications where high accuracy is required. Lithium chloride has a lower ionic strength than potassium chloride, which can reduce interference from other substances in the sample solution.
In summary, the electrolyte in a dissolved oxygen probe is a critical component that enables the transfer of electrons between the probe’s electrode and the sample solution. The most common electrolyte used is potassium chloride, which provides the necessary ions to generate an electrical current proportional to the oxygen concentration. Sodium sulfite is another type of electrolyte that can be used, which acts as a reducing agent to remove dissolved oxygen from the electrolyte solution itself. Other types of electrolytes, such as lithium chloride, may be used in specialized applications where high accuracy is required.