研究目的
To measure methanol content in aqueous solutions by NIRS combined with aquaphotomics, specifically at low concentrations (0.1%-2.5% v/v), and to prove the feasibility of this method for accurate and timely determination in fermentation processes.
研究成果
NIRS combined with aquaphotomics is feasible for quantitative analysis of low-concentration methanol in aqueous solutions, with high accuracy (R2 up to 0.999 and low RMSE values). The subtraction in turn method improved spectral quality, and aquaphotomics allowed identification of water matrix coordinates sensitive to methanol presence. This approach offers a rapid, non-destructive alternative to traditional methods like gas chromatography, but further research is needed for application in complex fermentation environments.
研究不足
The study was conducted on simple aqueous solutions of methanol and water, which may not fully represent the complexity of actual fermentation processes where biomass and metabolites could interfere. Environmental factors like temperature and light could affect spectral accuracy, and the method's applicability to real fermentation systems needs further validation.
1：Experimental Design and Method Selection:
The study used Fourier-transform near infrared (FT-NIR) spectroscopy combined with aquaphotomics to analyze low-concentration methanol in aqueous solutions. Partial least squares regression (PLSR) models were employed for quantitative analysis, and three subtraction methods were compared to improve spectral quality.
2：Sample Selection and Data Sources:
Deionized water and methanol were used to prepare water-methanol mixtures with concentrations from
3：1% to 5% (v/v) in increments of 1%. Four independent replicates were prepared:
two by direct dilution and two by serial dilution, resulting in 100 samples total.
4：List of Experimental Equipment and Materials:
Equipment included an Antaris II FT-NIR spectrometer (Thermo Fisher Scientific Inc., USA), a Millipore Milli-Elix/RiOs ultra-pure water system (Bedford, MA, USA), a quartz cuvette cell with 1.0 mm pathlength, and a temperature-controlled cell holder. Materials included deionized water and methanol (guaranteed reagent from Shandong Yuwang Industrial Company Limited).
5：0 mm pathlength, and a temperature-controlled cell holder. Materials included deionized water and methanol (guaranteed reagent from Shandong Yuwang Industrial Company Limited).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Spectra were collected in transmission mode from 10000 to 4000 cm?1 at 30°C. Each sample spectrum was averaged over 32 scans at 8 cm?1 intervals, and 10 consecutive spectra were recorded per sample to ensure stability. Background spectra were collected with air as reference before each sample measurement. Samples were measured over four days randomly to verify model stability.
6：Data Analysis Methods:
Data were processed using MATLAB 2015b, PLS_Toolbox_811, and OriginPro. Spectral pre-processing included autoscaling, mean center, first derivative, and Savitzky-Golay smoothing. PLSR models were built and evaluated using R2, RMSEC, RMSECV, and RMSEP, with 5-fold cross-validation and Kennard-Stone algorithm for sample splitting.
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