An adaptive absorption spectroscopy with adjustable moving window width for suppressing nonlinear effects in absorbance measurements

Jie Gao; Rui Zhu; Linying Li; Qiang Gao; Xijun Wu; Yucun Zhang; Yungang Zhang

doi:10.1016/j.saa.2023.122550

An adaptive absorption spectroscopy with adjustable moving window width for suppressing nonlinear effects in absorbance measurements

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Jun 5:294:122550. doi: 10.1016/j.saa.2023.122550. Epub 2023 Feb 24.

Authors

Jie Gao¹, Rui Zhu¹, Linying Li¹, Qiang Gao², Xijun Wu¹, Yucun Zhang¹, Yungang Zhang³

Affiliations

¹ School of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China.
² School of Tianjin University, State Key Laboratory of Engines, Tianjin 300072, China.
³ School of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China. Electronic address: zhangyg@ysu.edu.cn.

PMID: 36857866
DOI: 10.1016/j.saa.2023.122550

Abstract

Absorption spectroscopy based on Lambert-Beer law has been widely used in material structure analysis, research in chemical reaction kinetics, and exploration of various physicochemical reaction mechanisms. However, serious nonlinearity between absorbance and measured concentration can occur in actual measurements. The idea of moving window is first introduced into the field of spectral nonlinearity in the paper. Combining with the characteristic absorption spectra of the substances to be measured, we propose an adaptive absorption spectroscopy (A-AS) with adjustable moving window parameters to effectively suppress the nonlinear effects in absorbance measurements. The validity of this method is verified by taking the differential optical absorption spectroscopy to detect SO₂ as an example. The 210-230 nm characteristic absorption band is traversed and divided by the moving window with adjustable parameters, and the estimated coefficient (k-value) of each band is calculated. On this basis, all k-values are initially and secondly screened to obtain the optimal k_best, and then the optimal concentration value is obtained by inversion. Compared with the broad-band method and narrow-band method, it shows excellent performance that the maximum error and standard deviation of A-AS is only 1.3% and 3.8 in the entire concentration range, suggesting good linearity and stability in both high and low concentration environments. Therefore, it is inferred that A-AS is universally adaptable and enables dynamic linear measurements over wide concentration range.

Keywords: Adaptive absorption spectroscopy; Adjustable width moving window; Nonlinear correction; Optimal value screening.