title: Standard addition/absorption detection microfluidic system for salt error-free nitrite determination.
abstract: A continuous-flow microfluidic chip-based standard addition/absorption detection system has been developed for accurate determination of nitrite in water of varying salinity. The absorption detection of nitrite is made via color development using the Griess reaction. We have found the yield of the reaction is significantly affected by salinity (e.g., -12% error for 30‰ NaCl, 50.0 μg L(-1)N-NO2(-) solution). The microchip has been designed to perform standard addition, color development, and absorbance detection in sequence. To effectively block stray light, the microchip made from black poly(dimethylsiloxane) is placed on the top of a compact housing that accommodates a light-emitting diode, a photomultiplier tube, and an interference filter, where the light source and the detector are optically isolated. An 80-mm liquid-core waveguide mounted on the chip externally has been employed as the absorption detection flow cell. These designs for optics secure a wide linear response range (up to 500 μg L(-1)N-NO2(-)) and a low detection limit (0.12 μg L(-1)N-NO2(-) = 8.6 nM N-NO2(-), S/N = 3). From determination of nitrite in standard samples and real samples collected from an estuary, it has been demonstrated that our microfluidic system is highly accurate (<1% RSD, n = 3) and precise (<1% RSD, n = 3).
authors: Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, 790-784, South Korea.
authors: Jae-Hoon
authors: JH
authors: Ahn
authors: Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, 790-784, South Korea.
authors: Kyoung Ho
authors: KH
authors: Jo
authors: Department of Chemistry, BioNanotechnology Center, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, 790-784, South Korea. Electronic address: hahn@postech.ac.kr.
authors: Jong Hoon
authors: JH
authors: Hahn
mesh_terms: D000327:Adsorption; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D004784:Environmental Monitoring / Q000295:instrumentation; D004867:Equipment Design; D063366:Estuaries; D057230:Limit of Detection; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D009573:Nitrites / Q000032:analysis*; D054712:Salinity; D014867:Water / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D004129:Dimethylpolysiloxanes; D009573:Nitrites; D014874:Water Pollutants, Chemical; D014867:Water; C013830:baysilon
keywords: Absorption detection; Griess reaction; Microfluidic chip; Nitrite; Salt error; Standard addition