Chemometrics: An Excavator in Temperature-Dependent Near-Infrared Spectroscopy

Temperature-dependent near-infrared (NIR) spectroscopy has been developed and taken as a powerful technique for analyzing the structure of water and the interactions in aqueous systems. Due to the overlapping of the peaks in NIR spectra, it is difficult to obtain the spectral features showing the structures and interactions. Chemometrics, therefore, is adopted to improve the spectral resolution and extract spectral information from the temperature-dependent NIR spectra for structural and quantitative analysis. In this review, works on chemometric studies for analyzing temperature-dependent NIR spectra were summarized. The temperature-induced spectral features of water structures can be extracted from the spectra with the help of chemometrics. Using the spectral variation of water with the temperature, the structural changes of small molecules, proteins, thermo-responsive polymers, and their interactions with water in aqueous solutions can be demonstrated. Furthermore, quantitative models between the spectra and the temperature or concentration can be established using the spectral variations of water and applied to determine the compositions in aqueous mixtures.

SPECTROPOLYARIMETRY OF AQUEOUS MIXTURES OF HYDROCARBONS

Запропоновано застосувати спектрополяриметричний метод для визначення складу суміші водорозчинних вуглеводнів, кожний із яких володіє оптичною активністю. Метод може широко практикуватися для аналізу такої суміші природного походження, як мед. У конструкції поляриметра використано сучасні стабільні джерела світла – суперлюмінесценті світлодіоди. Під час вимірювань нема потреби в механічних рухомих деталях, що підвищує стабільність та швидкодію пристрою. Ключові слова: спектроскопія ядерного магнітного резонансу, рідинна хроматографія, оптична активність.

Preparation of Ceria-Coated Silica Nanoparticles and Their Chemical Mechanical Planarization Performance on Si-Face 6H-SiC Substrates

Ceria-coated silica (SiO2/CeO2) composite abrasives were prepared through a novel homogeneous precipitation method using commercial silica (SiO2) sol as the silicon resource and cerium nitrate (Ce(NO3)3) and hexamethylenetetramine (HMT) aqueous mixtures as coating precursors. The phase composition, nano-topography, size distribution, and chemical structure of as-prepared particles were characterized by X-ray diffraction, transmission electron microscopy, Zetasizer Nano ZS90 and Fourier infrared spectra. In addition, the possible coating mechanism was discussed. Then, chemical mechanical planarization behaviors of SiO2 sol, ceria (CeO2) sol, and the novel abrasives and on Si-face (0001) 6H-SiC were investigated by atomic force microscopy. The results indicated that the composite particles were mono-dispersed nano-spheres composed of amorphous SiO2 core and cubic fluorite CeO2 shell, possessing complete core-shell structure and particle size of about 110 nm. CeO2 shell (10 nm) grew on the surface of SiO2 core by formation of Ce-O-Si chemical bonds, forming stable core-shell structure. SiO2/CeO2 composite abrasives provided an exponentially high material remove rate (MRR) of 1207 nm/h and an impressive surface finish with roughness average (Ra) 0.216 nm due to its active chemical property and unique structure.

Solubility of Cinnarizine in (Transcutol + Water) Mixtures: Determination, Hansen Solubility Parameters, Correlation, and Thermodynamics

Between 293.2 and 313.2 K and at 0.1 MPa, the solubility of the weak base, cinnarizine (CNZ) (3), in various {Transcutol-P (TP) (1) + water (2)} combinations is reported. The Hansen solubility parameters (HSP) of CNZ and various {(TP) (1) + water (2)} mixtures free of CNZ were also predicted using HSPiP software. Five distinct cosolvency-based mathematical models were used to link the experimentally determined solubility data of CNZ. The solubility of CNZ in mole fraction was increased with elevated temperature and TP mass fraction in {(TP) (1) + water (2)} combinations. The maximum solubility of CNZ in mole fraction was achieved in neat TP (5.83 × 10−2 at 313.2 K) followed by the minimum in neat water (3.91 × 10−8 at 293.2 K). The values of mean percent deviation (MPD) were estimated as 2.27%, 5.15%, 27.76%, 1.24% and 1.52% for the “Apelblat, van’t Hoff, Yalkowsky–Roseman, Jouyban–Acree, and Jouyban–Acree–van’t Hoff models”, respectively, indicating good correlations. The HSP value of CNZ was closed with that of neat TP, suggesting the maximum solubilization of CNZ in TP compared with neat water and other aqueous mixtures of TP and water. The outcomes of the apparent thermodynamic analysis revealed that CNZ dissolution was endothermic and entropy-driven in all of the {(TP) (1) + water (2)} systems investigated. For {(TP) (1) + water (2)} mixtures, the enthalpy-driven mechanism was determined to be the driven mechanism for CNZ solvation. TP has great potential for solubilizing the weak base, CNZ, in water, as demonstrated by these results.

Estimating Activity Coefficients of Target Components in Poorly Specified Mixtures with NMR Spectroscopy and COSMO-RS

Poorly specified mixtures are common in process engineering, especially in bioprocess engineering. The properties of such mixtures of unknown composition cannot be described using conventional thermodynamic models. The NEAT method, which has recently been developed in our group, enables the calculation of activity coefficients of known target components in such poorly specified mixtures. In NEAT, the group composition of the mixture is determined by NMR spectroscopy and a thermodynamic group contribution method is used for calculating the activity coefficients. In all previous studies with NEAT, the UNIFAC group contribution method was used. In the present work, we demonstrate that NEAT can also be applied with another important method for predicting activity coefficients: COSMO-RS. COSMO-RS (OL) developed in Oldenburg together with its group contribution version GC-COSMO-RS (OL) is used here. The new version of NEAT was successfully tested. For a variety of aqueous mixtures excellent agreement of the NEAT predictions, for which only information on the target component was used, with results that were obtained using the full knowledge on the composition of the mixture was found. The results demonstrate the generic nature of the idea of NEAT and the broad applicability of the method.