Ultraviolet-Persulfate Oxidation Method for TOC Analysis in Water

The ultraviolet (UV)-persulfate oxidation method is a highly effective and widely adopted technique for determining Total Organic Carbon (TOC) in water samples. Its core principle involves the advanced chemical oxidation of organic compounds into carbon dioxide (CO₂) for precise measurement. This method is renowned for its ability to thoroughly degrade a wide spectrum of organic molecules, providing accurate and reliable TOC values.

The Oxidation Process
The process begins by acidifying the water sample and purging it with an inert gas to strip away inorganic carbon (IC), ensuring the measurement reflects only organic carbon. The sample is then introduced into a reaction chamber containing a persulfate reagent (e.g., sodium persulfate). When exposed to intense ultraviolet light, the persulfate ions (S₂O₈²⁻) are activated and break apart to form highly reactive sulfate radicals (SO₄•⁻). These powerful radicals aggressively oxidize and mineralize virtually all organic pollutants—from simple sugars to complex synthetic chemicals—converting their carbon content into carbon dioxide gas.

Detection and Measurement
The carbon dioxide gas produced from the oxidation reaction is carried by a stream of carrier gas to a detection system, most commonly a non-dispersive infrared (NDIR) sensor. The NDIR detector quantitatively measures the concentration of CO₂, which is directly proportional to the amount of organic carbon originally present in the water sample. This value is then calculated and reported as the TOC concentration.

Advantages and Applications
The key advantages of this method include its high oxidation efficiency for even recalcitrant organic compounds, excellent accuracy, and suitability for automation, allowing for rapid and high-throughput analysis. Due to these benefits, the UV-persulfate oxidation method is a benchmark technique for TOC monitoring in critical applications such as ensuring drinking water safety, validating wastewater treatment efficiency, and verifying water purity in the pharmaceutical and semiconductor industries.