Onsite quantifying electron donating capacity of dissolved organic matter.

Electron donating capacity (EDC) of dissolved organic matter (DOM) impacts the redox behaviors of DOM in surface waters, groundwaters, wetlands, sediments and soils but lacks applicable onsite quantification methods. To address these disadvantages, a simple and portable device with pre-injected [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonicacid), ABTS·] was developed that can be used for EDC onsite measurements of DOM in this work. The proposed device and method had better limits of quantification of Trolox (0.2 nmol) and more flexible DOC concentration requirement of 0.5-20 mg L than that of flow injection analysis (FIA) (5-10 mg L) or mediated electrochemical oxidation (MEO) (>20 mg L). The proposed device and method greatly reduced the preparation and measurement time for sample tests compared to MEO or FIA method, enabling time-efficient EDC determination for large amount of samples. Meanwhile, the proposed device presented comparable accuracy with established MEO method when quantifying the EDCs of 7 standard humic and fulvic acids. Humic acids with higher molecular weight (MW) (<15,000 Da) had higher EDC than that with low MW (<5000 Da). EDCs of DOM in natural and reclaim water samples were both presented significantly positive correlations with their corresponding chemical oxygen demand, chromophoric DOM content, molecular weight and humification of the DOM in water samples. These results suggested that our device could accurately quantify the EDCs of DOM onsite and had promising applications on the fast quality assessment of natural and reclaimed waters.