Advances in Science and Technology Vol. 115

Abstract: The synthesis of acid-activated Al₂O₃-pillared bentonite as a solid acid catalyst has been completed. The pillarization process was carried out using the varying pf calcination time, mole OH/Al ratio, and mmol of Keggin/bentonite to determine the optimum total acidity. The higher the calcination time, (OH/Al) ratio, and suspension concentration, the greater the acidity of ​​the Al₂O₃-pillared bentonite. The optimum conditions were achieved at a calcination time of 20 minutes, a mol of (OH/Al) ratio of 2.2, and Keggin/bentonite of 10 mmol with a total acidity of 11.76 mmol gram ammonia and 2.44 mmol/gram pyridine. The pillared bentonite had a surface area of ​​154.64 m²/g and a pore diameter of 3.38 nm. The pillaring process was successfully increasing the basal spacing of natural bentonite from 14.77 to 17.78.

Abstract: Dispersions of molybdenum-tungsten blues are promising precursors for the preparation of carbide catalysts by the sol-gel method. Stable systems were synthesized using ascorbic acid as a reducing agent at various molar ratios (Mo) :( W) = 100; 95: 5; 90:10; 80:20; 50:50. To study the properties of colloidal systems, UV / Vis spectroscopy, dynamic light scattering and electrophoretic light scattering were used. It was found that molybdenum-tungsten blue particles with different molar ratios of molybdenum and tungsten have a constant hydrodynamic radius equal to 2.0 nm. In the pH range (0.8 - 3.0) molybdenum-tungsten blue particles are negatively charged; the absolute values of the ζ-potential do not exceed 25 mV.

Abstract: The HPLC chiral separation of hydroxychloroquine (HCQ) using chiral α-1-acid glycoprotein (AGP) column has been predicted based on a molecular docking approach. The research begins with the geometrical optimization of the HCQ compound using the quantum calculation method of semiempirical (SE) of PM6, AM1, and PM3, and Hartree-Fock (HF) and density functional theory (DFT/B3LYP) with the basis set of 3-21G, 6-31G, and 6-311G. Molecular docking was performed with AutoDock Vina and PyRx applications on exhaustiveness of 264. Redocking with AutoDock Vina was done using coordinates of X = 13.584; Y = 1.47; Z = 18.451 with a grid box size of 40 x 40 x 40 and a grid Spacing of 0.375 Å, followed by specific docking process using the same conditions as redocking. The DFT method with the basis set of 6-311G was the best calculation method because it gives the lowest PRESS and closest r² value to one for the comparison between calculated and experimental data of ¹H-NMR. The docking result shows that R-HCQ enantiomer has more negative value of binding energy and more diverse interactions in the inclusion complex, indicating that R-HCQ forms more stable complex with AGP, and therefore it will be retained longer in the AGP column and eluted from the column later after R-HCQ.

Abstract: A study of the molecular anchoring and inclusion complex of the R/S-ibuprofen chiral compound with α-1-acid glycoprotein (AGP) has been carried out. This study aimed to predict the chiral separation of ibuprofen using chiral column filled with AGP protein. The geometrical optimization of R/S-ibuprofen was conducted on different calculation methods to obtain the optimal molecular structure. Molecular docking approaches, specifically docking using AutodockTools software were used to predict R/S-ibuprofen separation in AGP chiral column by comparing the binding energy values and the type of interaction. Results of the study show that the best method for optimizing the geometry of ibuprofen is Density Functional Theory (DFT). Furthermore, the results of the specific anchoring of ibuprofen on the AGP shows that the binding energy of S-ibuprofen with AGP is more negative than that of R-ibuprofen, namely -5.63 and -5.55 kcal/mol, respectively, indicating that S-ibuprofen interacts more strongly with AGP and therefore it will be eluted from the AGP chiral column later after R-ibuprofen.

Abstract: Prediction of chiral separation of R- and S-ketorolac has been carried out using a molecular docking approach. Geometry optimization using different calculation methods suggests that Hartree-Fock (HF)/6-31G is the best method to describe the most stable ketorolac structure. Docking studies have been performed on AutoDock and Gaussian software. Molecular docking results were used to predict the separation of ketorolac enantiomers in the AGP (alpha-1-acid-glycoprotein) chiral column by comparing the binding energies and types of interaction. To ensure the accuracy of the results, not only specific docking was performed, but blind docking was also conducted in this study. The results of the study show that the binding energy of S-ketorolac is more negative than that of R-ketorolac, indicating that stronger interaction between S-ketorolac and AGP occurs. Therefore, the R-ketorolac will be eluted first from the AGP column followed by S-ketorolac. As expected, this prediction is in good agreement with the experimental results of the separation of ketorolac enantiomers.

Abstract: A novel leaky waveguide grating (LWG) biosensor is reported where a continuous waveguide film of chitosan was photo patterned, resulting in a periodic modulation of the concentration of recognition elements (streptavidin in this case). This resulted in a periodic variation in the refractive index of the waveguide film, forming a phase grating at resonance angles of the LWG. Thus, a diffraction pattern was observed at resonance angles, but not at other angles. The position of resonance angles and hence diffraction pattern was a function of the refractive index of chitosan waveguide strips, forming the basis of biosensing and quantitative measurements.

Abstract: Visible-Near Infrared (Vis-NIR) spectroscopy combined with partial least squares discriminant analysis (PLS-DA) was used to classify Arabica and Robusta roasted coffee beans. The number of coffee beans analyzed was 200 samples consisting of 5 origins (Flores, Temanggung, Aceh Gayo, Jawa, and Toraja). Reflectance spectra with a wavelength of 450-950 nm were used to build two types of models, namely single-origin and general models. Single-origin Flores, Temanggung, Aceh Gayo, and Toraja models performed very well to classify coffee beans samples from the same origin with Sen, Spe, Acc, and Rel of 1, as well as TFN and TFP of 0. General PLS-DA model with baseline correction pretreatment yields Sen, Spe, Acc, and Rel of 0.97, as well as TFN and TFP of 0.04. Based on this paper, it was concluded that Vis-NIR combined with PLS-DA perform well in classifying roasted coffee beans based on the variety.

Abstract: CMC/Bentonite/N-P-K composites have been prepared as the macronutrient slow-release fertilizer. The composites were made by mixing natural bentonite, carboxymethyl cellulose (CMC), and N-P-K using a twin-screw extruder at 100 °C and screw rate of 600 rpm. The weight ratio of CMC to N-P-K was set at 1:0.5. The mass of bentonite was varied at 0.1; 0.5; and 1 (wt.%). The composites were characterized using infrared (IR) spectroscopy and X-ray diffraction (XRD). Mechanical properties of the composites were evaluated through tensile and compressive strength, water absorption capacity and stability test in water. It is found that increasing the natural bentonite ratio in the composite decreased the tensile and compressive strength but increased water absorption capacity and stability. The release of N-P-K from CMC/Bentonite/N-P-K followed the kinetic release model of pseudo-second-order.