Analytical Sciences

Online TOC Analysis Based on Reagent-free Oxidation of Dissolved Organic Matter Using a Mercury Lamp-Pass-Through Photoreactor

Takayuki SATOU, Tetsuya NAKAZATO, and Hiroaki TAO

Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan

The reagent-free mineralization of dissolved organic matter (DOM) in river water was achieved within 1 min using a lamp-pass-through photoreactor containing a narrow reaction tube (2 mm i.d.) passing through a 40 W mercury lamp. The structure efficiently irradiated the sample solution in the tube with vacuum ultraviolet (VUV; 185 nm) light from the lamp, which rapidly decomposed the DOM with hydroxyl radicals generated efficiently from the water and oxygen that are naturally present in the solution. The photoreactor was also applicable to oxidizing reagent-free online toatal organic carbon (TOC) analysis of DOM in river-water samples using a non-dispersive infrared radiation detector after acidification of the sample using 20 mmol L⁻¹ phosphoric acid. The detection limit for phthalate at the injection of 390 μL was 6.2 μg of carbon L⁻¹. The repeatability, as expressed by the relative standard deviation, was 2.5% for thrice-repeated analyses of a river sample with 1.85 mg of carbon L⁻¹.

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