Determination of atmospheric hydroxyl radical by HPLC coupled with electrochemical detection

The hydroxyl radical (center dot OH) plays a central role in the oxidation and removal of many atmospheric compounds. Measurement of atmospheric center dot OH is very difficult because of its high reactivity and low atmospheric abundance. In this article, a simple and highly sensitive method, high performance liquid chromatography coupled with coulometric detection (HPLC-CD), was developed to determine center dot OH indirectly by determining its reaction products with salicylic acid (SAL), 2,3-dihydroxybenzoic acid (2,3-DHBA), and 2,5-dihydroxybenzoic acid (2,5-DHBA). Under the optimum conditions for its determination, 2,3-DHBA and 2,5-DHBA could be well separated and the detection limits for 2,3-DHBA were 3 x 10(-10) mol/L and for 2,5-DHBA were 1.5 x 10(-10) mol/L, which were lower than most previous reports. This method was also applied to measure atmospheric hydroxyl radical levels and demonstrated the feasibility in clean and polluted air.