Experimental study on novel phase change composites for thermal energy storage

Journal of Thermal Analysis and Calorimetry - In this study, beeswax is studied as a phase change material (PCM) to store heat due to its high latent heat. The disadvantages of using beeswax were...     

Quantitative determination of isoquinoline alkaloids and chlorogenic acid in Berberis species using ultra high performance liquid chromatography with hybrid triple quadrupole linear ion trap mass spectrometry

Berberis species are well known and used extensively as medicinal plants in traditional medicine. They have many medicinal values attributable to the presence of alkaloids having different pharmacological activities. In this study, a method was developed and validated as per international conference on harmonization guidelines using ultra high performance liquid chromatography with hybrid triple quadrupole‐linear ion trap mass spectrometry operated in the multiple reaction monitoring mode for nine bioactive compounds, including protoberberine alkaloids, aporphine alkaloids and chlorogenic acid. This method was applied in different plant parts of eight Berberis species to determine variations in content of nine bioactive compounds. The separation was achieved on an ACQUITY UPLC CSH? C₁₈ column using a gradient mobile phase at flow rate 0.3 mL/min. Calibration curves for all the nine analytes provided optimum linear detector response (with R² ≥0.9989) over the concentration range of 0.5–1000 ng/mL. The precision and accuracy were within RSDs ≤2.4 and ≤2.3%, respectively. The results indicated significant variation in the total contents of the nine compounds in Berberis species.     

Vasicine as tridentate ligand for enantioselective addition of diethylzinc to aldehydes

The first report of natural l-vasicine as tridentate chiral ligand for the enantioselective addition of diethylzinc to a variety of aliphatic and aromatic aldehydes is described. The ligand generates R-isomer of the secondary alcohols upto 98% ee. The quinazoline structure possibly imparts rigidity to the ligand and hence, consistently high enantioselectivity. The importance of the quinazoline ring was also supported by the reaction with other related ligands, partially lacking the structural features, thus resulting in poor enantioselectivity.     

X-ray topography, photopyroelectric and two-photon absorption studies on solution grown benzimidazole single crystal

Benzimidazole (BMZ) is an organic nonlinear optical material, and it is possible to grow it in the laboratory by a slow evaporation solution growth technique using methanol as the solvent. Its nonlinear optical harmonic generation efficiency is 4.5 times higher than that of standard potassium dihydrogen phosphate (KDP) single crystal. It crystallizes with orthorhombic structure, which is noncentrosymmetric in nature, with lattice parameters a=13.58 Å, b=6.85 Å, c=6.97 Å. The functional groups of the grown specimen are confirmed by heteronuclear chemical shift correlation (HETCOR) analysis and it is found that other elements are not incorporated in the compound. The crystalline perfection is examined by high resolution X-ray diffraction (HRXRD), and its topographic image was recorded for the as-grown single crystal indicates the presence of some grain boundaries in the grown specimen. Thermal parameters such as thermal diffusivity (α), thermal conductivity (k), thermal effusivity (e), and heat capacity (c _p ) have been determined by a photopyroelectric thermal wave method. In addition, piezoelectricity, birefringence, and third-order nonlinear optical properties have been examined. The two-photon absorption coefficient of the title compound is determined by the open-aperture Z-scan technique.     

A validated liquid chromatographic method for estimation of solasodine in various Solanum species and market formulations

This paper describes an improved liquid chromatographic (LC) method involving a prechromatographic derivatization step for the estimation of solasodine from berries of various Solanum species, market samples of Solanum xanthocarpum herb, extract, and its market formulations. Solasodine has heterocyclic nitrogen but has no conjugated double bonds in its structure. However, in all reported LC methods, detection was made in the ultraviolet range of 200-213 nm. In the present study, a prechromatographic derivatization of solasodine was done by forming an ion-pair complex of the heterocyclic nitrogen using the acidic dye methyl orange and acetate buffer of pH 4.7. Detection could be made in the visible range at 530 nm in this method. The method was validated and successfully applied to determine solasodine content in various plant samples and polyherbal formulations. The relative standard deviation was found to be 0.025% for system precision, and 0.8% for the linearity of the method, and the correlation coefficient was 0.999. Plant samples and market formulations were analyzed and found to contain solasodine in the range of 0.113-0.227% (w/w) on a fresh weight basis in berries; 0.3-1.278% (w/w) and 0.412% (w/w) on a dry weight basis in S. xanthocarpum herb powder and extract, respectively; and 0.245-0.525% (w/w) on dry weight basis in formulations containing S. xanthocarpum herb powder. No matrix interference was encountered. The method was found to be accurate, with a mean recovery of 100.5 +/- 0.83%. The method has good reproducibility and was found to be suitable for estimation of solasodine.     

Polarization studies by the TSC technique on a blend of cellulose acetate and polyvinyl acetate

The thermally stimulated current (TSC) technique has been used to study solvent-cast blends of a cellulose derivative with a vinyl polymer. TSC peaks are observed at 56, 80, and 120°C. Their origin is investigated because the TSC spectra of the blends differ from the spectra of the individual components. Data on blends with components in the weight ratios 25:75, 50:50, and 75:25 indicate that the 50:50 blend shows the greatest polarization. The enhancement of depolarization currents observed on blending is explained on the basis of a Maxwell–Wagner–Sillars polarization due to increased heterogeneity in the structure. Effects of forming conditions (time, temperature, field) on polarization have been investigated. Activation energies and relaxation times are calculated; there is good agreement between the values obtained from the initial-rise and the full-curve methods.     

Effect of metal cationization on the tandem mass spectra of glycosyl dithioacetals

The effect of metal cationization on the tandem mass spectra of glycosyl dithioacetals of glucose, mannose, galactose, rhamnose, arabinose and xylose was studied by electrospray ionization mass spectrometry under ammonium and metal (Li, Na, Ag and Cu) ion cationization conditions. The ammonium-cationized glycosyl dithioacetals fragment by loss of ammonia followed by either two molecules of EtSH or one molecule of EtSH and one molecule of H2O. Lithium cationization leads to additional eliminations such as EtSEt and EtSSEt and C-C cleavages. Elimination of EtSH is not observed under sodium cationization. Silver cationization, on the other hand, leads to additional fragmentations involving the elimination of silver as AgOH and AgSEt. Copper cationization results in adducts where copper has undergone a change of oxidation state from II to I. Li+, Ag+ and Cu+ cationization seem to favour cyclization resulting in elimination of EtSH. However, the mechanisms seem to be differently affected by different metal ions. Li+ and Ag+ cationization appear to be non-specific and favour cyclization involving C2-, C4- and C5-hydroxyl hydrogens, whereas Cu+ cationization seems to favour cyclization involving C4-hydroxyl hydrogen.     

2,3-Unsaturated allyl glycosides as glycosyl donors for selective α-glycosylation

In the presence of NBS and a catalytic amount of a Lewis acid, 2,3-unsaturated allyl glycosides [6-(allyloxy)-3,6-dihydro-2-(hydroxymethyl)-2H-pyran-3-ol] have been successfully used as versatile glycosyl donors for the stereoselective α-glycosylation of a variety of alcohols comprising sensitive functions such as acetonide, keto, nitro, and ester in 50-90% yields. The methodology offers an equally facile alternative to 4-pentenyl replacement in unsaturated sugars.