Evaluating the Molecular Interaction of Organic Liquid Mixtures Using Near-Infrared Spectroscopy

Abstract

The near-infrared transmission spectra of two organic liquid three-component systems of variable compositions were investigated in detail. To evaluate the interaction of the different components in the two systems the experimental spectra of the pure components were compared to mathematically constructed "pure component" spectra. Though usually the correlation coefficient (CC) and Manhattan distance (MD) are used to measure the similarity of spectra, in the present investigations principal component analysis (PCA) was found to be a more effective tool to investigate the difference between these spectra and derive parameters characterizing the interaction between the different components. Thus, PC scores for the two types of spectra established some distinct patterns which clearly expressed their differences. For a three-dimensional coordinate system of selected principal components, the Euclidean distances between the mathematically constructed and the experimental spectra of the pure components were calculated. Finally, the mean values of the distances for each component provided indices to rank the interaction of the components in the mixtures. Thus, the results offer a convenient approach that can quantitatively evaluate the molecular interactions of the individual components in organic liquid mixtures by various spectroscopies.

Quantitative Analysis of Organic Liquid Three-Component Systems: Near-Infrared Transmission versus Raman Spectroscopy, Partial Least Squares versus Classical Least Squares Regression Evaluation and Volume versus Weight Percent Concentration Units

“…This is a consequence of the fact, that contrary to NIR spectroscopy, the Raman technique does slightly reflect spectral changes by molecular interactions of the mixture components of system 1 in the form of small band shifts of skeletal and ring breathing vibrations. Using a similar approach of pure-spectra reconstruction with the Raman spectra of system 1 as described in detail in a previous publication for NIR spectra [5], these interaction effects are observed as dispersion shaped signals.…”

“…Due to the different physical excitation mechanisms of mid-infrared (MIR)/NIR and Raman spectra, molecular interaction in multicomponent systems (e.g., hydrogen bonding) can affect these types of vibrational spectra to different extents. Hydrogen bonding plays a vital role in the molecular interaction of OH and NH groups with carbonyl or ether functionalities and has significant footprints in the MIR spectra of multicomponent systems with relevant chemistry [1,2,3,4,5]. These spectral effects, however, are not only observed with fundamental vibrations in the mid-infrared region but also occur in the overtone and combination band region of the near-infrared [6].…”

Identification of textiles by handheld near infrared spectroscopy: Protecting customers against product counterfeiting

“…Generally, the larger the Euclidean distance between two clusters, the better the respective classes can be discriminated and identified. 37 Thus, PCA models were developed for the 36 possible textile pairs based on the first three PCs and the Euclidian distances between the center of corresponding clusters were calculated ( Table 3). The first three PCs were chosen for the derivation of the Euclidian distances, because they explained the majority of the variance of the X-variables (61.0%: Si-Ware Systems; 81.2%: Spectral Engines NR 2.0-W; 63.7%: DLP NIRscan Nano EVM; 69.5%: Viavi MicroNIR 1700).…”

Improvement of teaching near-infrared spectroscopic analysis for undergraduates

“…Therefore, it is widely applied in the fields of food, agricultural products, Chinese herbal medicines (traditional Chinese medicine (TCM)), petrochemical industry, and so on. 1–4 With the development of light-fiber coupled probes, NIR spectroscopy has also quickly expanded into industrial production as a process-control tool. Especially with the development of micro-electro-mechanical system, miniaturization of NIR instruments has advanced significantly and, in the near future, will lead to the use of handheld instruments for everyday-life control procedures by ordinary customers.…”