FTIR/ATR Spectroscopy Applied to the Rapid Determination of Chemical Oxygen Demand of Wastewater

Abstract

A directly rapid quantification method for chemical oxygen demand (COD) of wastewater was established by Fourier transform infrared (FTIR) spectroscopy combined with attenuated total reflection (ATR) technology and moving window partial least squares (MWPLS) method with changeable parameters. All samples were firstly divided into the calibration set and the prediction set. And then according to the predicion effect, the optimal model was selected, and the corresponding waveband, number of adopted wavenumbers, PLS factor, root mean squared error of predication (RMSEP), correlation coefficient of predication (RP) were 3152-1109 cm-1, 1060, 8, 21.5 mg/L, and 0.981 respectively, which was obviously superior to the optimal PLS model on the whole spectral collecting region. The result shows that FTIR/ATR spectroscopy can be applied to the rapid determination of COD of wastewater, and the waveband selected by MWPLS method with changeable parameters has higher signal to noise ratio, which can effectively improve the precision of the predictive model.

A 3-Step Chemiluminescence Method for Chemical Oxygen Demand Measurement

“…[15][16][17] However, the back-titration process is still required, which is laborintensive, and the reproducibility is dependent on a laborous technique. Other analytical methods were reported for the measurement of COD, including atomic absorption spectrometry (AAS), 18,19 positive potential accompany with quartz UV lamp illumination applyied on a TiO2 photocatalytic sensor, Fourier-transform infrared (FTIR) spectroscopy combined with attenuated total-reflection (ATR) technology, 21 UV-vis spectroscopy combined with partial-least-squares regression, 22 near-infrared (NIR) transmission combined with the UV absorbance, 23 inductively coupled plasma optical emission spectrometry (ICP-OES) with microwave digestion, 24,25 and single-sweep polarography. 26 These methods require massive and expensive instruments and, hence, it is difficult to apply for on-site monitoring.…”