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Development of microfluidic absorbance detection system for monitoring of total dissolved phosphorus in water

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The compact, sensitive and continuous absorbance detection system for determination of total dissolved phosphorus (TDP) in aqueous media has been developed. The measurement of TDP in surface water and wastewater is critical for understanding eutrophication processes and biogeochemical cycling, asses...
The compact, sensitive and continuous absorbance detection system for determination of total dissolved phosphorus (TDP) in aqueous media has been developed. The measurement of TDP in surface water and wastewater is critical for understanding eutrophication processes and biogeochemical cycling, assessing water quality in drinking water reservoirs. As a common method for determination of TDP, all kinds of dissolved phosphorus should be converted to orthophosphate form which is detectable at 370 nm. At the first step, the conversion process is accomplished by addition of an oxidant under UV irradiation. The following step is for the microfluidic chip-based absorbance detection with color development. To take an advantage on flexibility of a light path length, a liquid core waveguide (LCW) is adopted. The LCW made of Teflon AF-2400 has been used to extend the sensitivity of conventional colorimetric method. The linear range and limit of detection for TDP are 0.5–4 ppm (R2 = 0.999) and 0.3 ppm (S/N = 3) respectively. Especially, standard addition method is applied into the absorbance system to minimize analytical errors and expand the range of detectable samples. Black PDMS is used as the substrate in the fabrication of the microchip to eliminate interference of stray light. Furthermore, the system integrated with wireless communication will be particularly suited for environmental monitoring requiring high spatial or temporal resolution.