Determination of atmospheric hydroxyl radical by HPLC coupled with electrochemical detection

The hydroxyl radical (·OH) plays a central role in the oxidation and removal of many atmospheric compounds. Measurement of atmospheric ·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 ·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 × 10−10 mol/L and for 2,5-DHBA were 1.5 × 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.