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Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR) technology were successfully applied for the rapid no-reagent determination of chemical oxygen demand (COD) in sugar refinery wastewater. An appropriate waveband with stability was selected by the moving window partial least-squares (MWPLS) regression through a rigorous modeling process. The selected waveband was 3198 cm-1 to 2376 cm-1, the corresponding PLS factor was 5. The modeling effect M-SEPAve, M-RP,Ave, M-SEPStd, and M-RP,Std were 31.5 mg/L, 0.962, 3.9 mg/L, and 0.012, respectively. The validation effect V-SEP and V-RP were 31.9 mg/L and 0.965, respectively. It indicated that the method has good prediction effect and stability, and provided valuable references for designing specialized spectroscopic instruments.

Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR) technology combined with the partial least squares (PLS) regression were successfully applied for the rapid no-reagent determination of chemical oxygen demand (COD) for sugar refinery wastewater. Among 105 samples, 45 samples were randomly selected as the validation set. The remaining 60 samples were divided into the calibration set (40 samples) and the prediction set (20 samples) for a total of 30 times with certain similarities. The appropriate model with stability was established on the waveband of 4500 cm-1to 600 cm-1. The optimal PLS factor was 4, the modeling effect M-SEPAve, M-RP,Ave, M-SEPStd, and M-RP,Stdwere 38.1 mg/L, 0.944, 3.2 mg/L, and 0.013, respectively, the validation effect V-SEP and V-RPwere 38.2 mg/L and 0.949, respectively, which has good prediction effect and stability. The results provide a reliable analytical model for the monitoring of COD in sugar refinery wastewater.

A directly rapid quantitative analysis method for chemical oxygen demand (COD) of wastewater was established by Fourier transform infrared (FTIR) spectroscopy and attenuated total reflection (ATR) technology. The combination selection of Savitzky-Golay (SG) smoothing modes combined with partial least squares (PLS) factor was applied to the model optimization here. The optimal smoothing parameters were 2ndorder derivative smoothing, 6thdegree polynomial and 51 smoothing points. The corresponding optimal PLS factor, root mean squared error of predication (RMSEP) and correlation coefficient of predication (RP) were 11, 24.4 (mg/L) and 0.968 respectively, which was obviously superior to the direct PLS model without SG smoothing. This demonstrated that the combination selection of SG smoothing parameters and PLS factor can be effectively applied to the model optimization for FTIR/ATR analysis of COD in wastewater.