Miniaturized TOC analyzer using dielectric barrier discharge for catalytic oxidation vapor generation and point discharge optical emission spectrometry

Kai Li; Hanjiao Chen; Zhiming Chen; Lin He; Xiandeng Hou; Xiaoming Jiang

doi:10.1016/j.aca.2021.338683

Miniaturized TOC analyzer using dielectric barrier discharge for catalytic oxidation vapor generation and point discharge optical emission spectrometry

Anal Chim Acta. 2021 Aug 8:1172:338683. doi: 10.1016/j.aca.2021.338683. Epub 2021 May 24.

Authors

Kai Li¹, Hanjiao Chen¹, Zhiming Chen², Lin He¹, Xiandeng Hou³, Xiaoming Jiang⁴

Affiliations

¹ Analytical & Testing Center, Sichuan University, Chengdu, Sichuan, 610064, China.
² Changqing Oilfield Branch Company Oil Production Plant NO.11, PetroChina Company Limited, Qingyang, Gansu, 745000, China.
³ Analytical & Testing Center, Sichuan University, Chengdu, Sichuan, 610064, China; Key Laboratory of Green Chemistry & Technology of MOE, and College of Chemistry, Sichuan University, Chengdu, Sichuan, 610064, China. Electronic address: houxd@scu.edu.cn.
⁴ Analytical & Testing Center, Sichuan University, Chengdu, Sichuan, 610064, China. Electronic address: jiangxm@scu.edu.cn.

PMID: 34119015
DOI: 10.1016/j.aca.2021.338683

Abstract

Total organic carbon (TOC) is an important parameter describing organic pollution degree of waters. Due to the increasing need of field analysis and drawbacks of conventional TOC analytical instruments, miniaturized TOC analyzers are still demanding. In this work, a dielectric barrier discharge (DBD) microplasma was utilized for catalytic oxidation vapor generation (COVG) of organic compounds into CO₂, and a point discharge (PD) microplasma was employed to excite the carbon atomic emission spectra for quantification. Sample solution with phosphoric acid and persulfate solution was injected into the DBD-COVG reactor by a syringe to convert organic compounds into CO₂ efficiently and quickly, which was subsequently transported into the point discharge optical emission spectrometer (PD-OES) for detecting carbon at 193.09 nm. Under optimal experimental conditions, high oxidation efficiencies for several organic compounds were achieved, i.e., 96.4%, 95.1% and 94.3% for 50 mg L^-1 potassium hydrogen phthalate (KHP), sodium laurylsulfonate and phenol, respectively. A limit of detection (LOD) of 0.02 mg L^-1 (as C) was obtained, with a precision of 3.9% (relative standard deviation, RSD) at 15 mg L^-1 TOC standard (as C). The possible catalytic oxidation mechanism was proposed with the characteristic results of electron paramagnetic resonance (EPR). Its potential environmental application was demonstrated by successfully analyzing TOC in underground water, surface river water and surface sedimentary water samples from oil fields, with analytical results agreed well with those obtained by the commercial high-temperature combustion coupled nondispersive infrared absorption (HTC-NDIR) technique.

Keywords: Catalytic oxidation vapor generation; Dielectric barrier discharge; Optical emission spectrometry; Point discharge; Total organic carbon.