Simultaneous determination of nitrate, chemical oxygen demand and turbidity in water based on UV-Vis absorption spectrometry combined with interval analysis

Xiaowei Chen; Gaofang Yin; Nanjing Zhao; Tingting Gan; Ruifang Yang; Meng Xia; Chun Feng; Yunan Chen; Yao Huang

doi:10.1016/j.saa.2020.118827

Simultaneous determination of nitrate, chemical oxygen demand and turbidity in water based on UV-Vis absorption spectrometry combined with interval analysis

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Jan 5:244:118827. doi: 10.1016/j.saa.2020.118827. Epub 2020 Aug 13.

Authors

Xiaowei Chen¹, Gaofang Yin², Nanjing Zhao³, Tingting Gan⁴, Ruifang Yang⁴, Meng Xia¹, Chun Feng¹, Yunan Chen¹, Yao Huang¹

Affiliations

¹ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; University of Science and Technology of China, Hefei 230026, China.
² Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China. Electronic address: gfyin@aiofm.ac.cn.
³ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China. Electronic address: njzhao@aiofm.ac.cn.
⁴ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.

PMID: 32862077
DOI: 10.1016/j.saa.2020.118827

Abstract

In this paper, a new method for simultaneous determination of nitrate, COD and turbidity in water based on UV-Vis absorption spectrometry combined with interval analysis was studied. By analyzing the spectral absorption characteristics of nitrate, COD, and turbidity standard solutions and the mixtures of them, the absorption spectra in the range of 225-260 nm, 260-320 nm and 320-700 nm were selected as the characteristic spectra of nitrate, COD and turbidity, respectively. Multiplicative scatter correction was employed to compensate turbidity of the absorption spectra of the mixture solutions in the wavelength range of 225-320 nm. Then, the spectra after turbidity compensation in the range of 225-260 nm was compensated for COD using the method of spectral difference. The original spectra in the range of 320-700 nm, the turbidity compensated spectra in the range of 260-320 nm, and the COD compensated spectra in the range of 225-260 nm were analyzed by PLS algorithm in order to calculate the concentrations of nitrate, COD and turbidity in the mixture solutions. The results showed that this method could simultaneously and accurately determine the concentrations of nitrate, COD and turbidity. After interval analysis, all the correlation coefficients (R²) between the predicted values and the true values of nitrate, COD and turbidity were higher than 0.9, and root mean square error (RMSE) of predicted values were between 0.696 and 2.337.

Keywords: COD; COD compensation; Interval analysis; Nitrate; Turbidity; Turbidity compensation; UV–Vis spectrum.