Degradation studies of organic acids in commercially packed fruit juices: A reverse phase high performance liquid chromatographic approach

Organic acids are important constituents of fruit juices. They render tartness, flavour and specific taste to fruit juices. Shelf life and stability of fruit juices are important factors, which determine their nutritional quality and freshness. In this view, the effect of storage on the concentration of organic acids in commercially packed fruit juices is studied by reverse phase high performance liquid chromatography (RP-HPLC). Ten packed fruit juices from two different brands are stored at 30 C for 24, 48 and 72 hours. A reverse phase high performance liquid chromatographic method is used to determine the concentration of oxalic, tartaric, malic, ascorbic and citric acid in the fruit juices during storage. The chromatographic analysis of organic acids is carried out using mobile phase 0.5% (w/v) ammonium dihydrogen orthophosphate buffer (pH 2.8) on C18 column with UV-Vis detector. The results show that the concentration of organic acids generally decreases in juices under study with the increase in storage time. All the fruit juices belonging to tropicana brand underwent less organic acid degradation in comparison to juices of real brand. Orange fruit juice is found to be least stable among the juices under study, after the span of 72 hours. Amongst all the organic acids under investigation minimum stability is shown by ascorbic acid followed by malic and citric acid.

Caryophyllene-Rich Essential Oil of Didymocarpus tomentosa: Chemical Composition and Cytotoxic Activity

The essential oil from the leaves of Didymocarpus tomentosa was extracted by hydrodistillation and analyzed by GC/FID and GC/MS. Twenty five constituents amounting to 81.6% of the oil were identified. The leaf oil contained 78.7% sesquiterpenes and 2.9% monoterpenes. The leaf essential oil of D. tomentosa is a unique caryophyllene-rich natural source containing beta-caryophyllene, caryophyllene oxide, alpha-humulene and humulene oxide. The cytotoxic activity of the oil was determined by the BSLT using shrimp larva and the MTT assay using HeLa tumor cell line. The oil showed significant cytotoxic activity with LC50 and IC50 values of 12.26 and 11.4 mu g/mL, respectively. This is the first report on the chemical composition and cytotoxic activity of the essential oil of D. tomentosa.

Photo and Thermal Degradation of a Cationic Superabsorbent Polymer

A cationic superabsorbent polymer (SAP) was synthesized by carrying out the polymerization of 2-(methacryloyloxy)ethyl] trimethyl ammonium chloride) with N,N'-methylenebisacrylamide as the cross-linking agent. The SAP was subjected to degradation in dry and the equilibrium swollen state by thermo gravimetric analysis and exposure to ultraviolet radiation, respectively. The photodegradation was monitored by measuring changes in the swelling capacity and the dry weight of the SAP. The thermal degradation of the SAP occurred in three stages after the initial removal of moisture and the activation energies of the decomposition were determined.

Thermal degradation kinetics of thermoresponsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers prepared via RAFT polymerization

Reversible addition-fragmentation chain transfer polymerization at 70 A degrees C in N,N-dimethylformamide was used to prepare poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers in various compositions to afford well-defined polymers with pre-determined molecular weight, narrow molecular weight distribution, and precise chain end structure. The copolymer compositions were determined by H-1 NMR spectroscopy. The reactivity ratios of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMA) were calculated as r (NIPAM) = 0.838 and r (DMA) = 1.105, respectively, by the extended Kelen-Tudos method at high conversions. The lower critical solution temperature of PNIPAM can be altered by changing the DMA content in the copolymer chain. Differential scanning calorimetry and thermogravimetric analysis at different heating rates were carried out on these copolymers to understand the nature of thermal degradation and to determine its kinetics. Different kinetic models were applied to estimate various parameters like the activation energy, the order, and the frequency factor. These studies are important to understand the solid state polymer degradation of N-alkyl substituted polymers, which show great potential in the preparation of miscible polymer blends due to their ability to interact through hydrogen bonding.

Synthesis, characterization and thermal degradation of dual temperature- and pH-sensitive RAFT-made copolymers of N,N-(dimethylamino)ethyl methacrylate and methyl methacrylate

Poly{(N,N-(dimethylamino)ethyl methacrylate]-co-(methyl methacrylate)} copolymers of various compositions were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization at 70 degrees C in N,N-dimethylformamide. The polymer molecular weights and molecular weight distributions were obtained from size exclusion chromatography, and they indicated the controlled nature of the RAFT polymerizations; the polydispersity indices are in the range 1.11.3. The reactivity ratios of N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) (rDMAEMA = 0.925 and rMMA = 0.854) were computed by the extended KelenTudos method at high conversions, using compositions obtained from 1H NMR. The pH- and temperature-sensitive behaviour were studied in aqueous solution to confirm dual responsiveness of these copolymers. The thermal properties of the copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. The kinetics of thermal degradation were determined by Friedmann and Chang techniques to evaluate various parameters such as the activation energy, the order and the frequency factor. (c) 2012 Society of Chemical Industry

Effect of Metal Ions (Ag, Co, Ni, and Pd) on the Visible Light Degradation of Rhodamine B by Carbon-Covered Alumina-Supported TiO2 in Aqueous Solutions

Metal-ion (Ag, Co, Ni, and Pd) doped TiO2 nanocatalysts were successfully embedded on carbon-covered alumina supports. The CCA-embedded catalysts were crystalline and had a high surface area compared to the free metal-ion doped titania nanocatalysts while they still retained the anatase phase of the core TiO2. These catalysts were photocatalytically active under solar light irradiation. Rhodamine B was used as a model pollutant and the reactivity followed a pseudo-first-order reaction kinetics. The reaction rate of the CCA-supported catalysts was Pd > Ag > Co > Ni. Among the ratios of the CCA:catalyst used, it was found that the 1:1 ratio had the fastest reaction rate, followed by the 1:2 ratio, while the 2:1 ratio exhibited the lowest reaction rate. The CCA/metal-ion doped titania were found to have photocatalytic activities comparable with those of CCA-supported titania.

Photocatalytic degradation with combustion synthesized WO3 and WO3-TiO2 mixed oxides under UV and visible light

The photocatalytic activity of commercial titanium dioxide under UV and visible radiation was improved by composites of tungsten trioxide (WO3) with TiO2. WO3 was prepared by solution combustion synthesis and the mixed oxides/composites of WO3-TiO2 were prepared in different weight ratios (0, 0.10, 0.15, 0.20, 0.25, 0.50, 0.75, and 1) by physical mixing. These catalysts were characterized by XRD, DRS, BET, SEM, TEM, pH drift method, TGA and photoluminescence. The photocatalytic activity varies with the WO3 loading in the composites. The optimum loading of WO3 in the composites was found to be 15 wt% for both UV and visible radiation. This loading showed faster dye degradation rate than commercial TiO2 (TiO2-C) and WO3 (WO3-C). The effect of initial concentrations of methylene blue (MB) and orange G (OG) and the effect of the functional group on dye degradation was studied with both anionic and cationic dyes with 15 wt% WO3-TiO2. (C) 2012 Elsevier B.V. All rights reserved.

Structure, tensile properties and cytotoxicity assessment of sebacic acid based biodegradable polyesters with ricinoleic acid

A new family of ricinoleic acid based polyesters was synthesized using catalyst free melt-condensation polymerization with sebacic acid, citric acid, mannitol and ricinoleic acid as precursors. The use of FT-IR and NMR characterisation techniques confirms the presence of ester linkages in the as-synthesized polymers. Depending on the precursor combination, their relative amount and the degree of curing, a broad range of elastic modulus (22-327 MPa) and tensile strength (0.7-12.7 MPa) can be obtained in the newly synthesized biopolymers. The polymers show rubbery behaviour at a physiological temperature (37 degrees C) and the contact angles of the synthesized polymers fall in the range of 42 degrees to 71 degrees, making them ideal substrates to study delivery of drugs through polymer scaffolds. The cytocompatibility assessment of the cured polymers confirmed good cell attachment and growth of smooth muscle cells (C2C12 myoblast cells). Importantly, oriented cell growth was observed after culturing myoblast cells for 3 days. The in vitro degradation in PBS indicates that the mild cured polymers follow a first order reaction kinetics and have degradation rate constants in the range of 0.009-0.038 h(-1), depending on the relative proportions of monomers. Overall, the results of our study indicate that the physical properties can be tailored by varying the composition of the monomers and curing conditions in the newly developed polyesters. Hence, they may be used as potential substrates for tissue engineering scaffolds and for localized drug delivery.

Effect of leachate recirculation and extent of degradation on the stability of bioreactor landfill slopes

The stability of a bioreactor landfill slope is influenced by the quantity and method of leachate recirculation as well as on the degree of decomposition. Other factors include properties variation of waste material and geometrical configurations, i.e., height and slope of landfills. Conventionally, the stability of slopes is evaluated using factor of safety approach, in which the variability in the engineering properties of MSW is not considered directly and stability issues are resolved from past experiences and good engineering judgments. On the other hand, probabilistic approach considers variability in mathematical framework and provides stability in a rational manner that helps in decision making. The objective of the present study is to perform a parametric study on the stability of a bioreactor landfill slope in probabilistic framework considering important influencing factors, such as, variation in MSW properties, amount of leachate recirculation, and age of degradation, in a systematic manner. The results are discussed in the light of existing relevant regulations, design and operation issues.

Effect of lipopolysaccharide on alteration of phospholipids and their fatty acid composition in spleen and thymus by in vitro metabolic labeling

Lipopolysaccharide (LPS) is an endotoxin, a potent stimulator of immune response and induction of LPS leads to acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). ARDS is a life-threatening disease worldwide with a high mortality rate. The immunological effect of LPS with spleen and thymus is well documented; however the impact on membrane phospholipid during endotoxemia has not yet been studied. Hence we aimed to investigate the influence of LPS on spleen and thymus phospholipid and fatty acid composition by 32P]orthophosphate labeling in rats. The in vitro labeling was carried out with phosphate-free medium (saline). Time course, LPS concentration-dependent, pre- and post-labeling with LPS and fatty acid analysis of phospholipid were performed. Labeling studies showed that 50 mu g LPS specifically altered the major phospholipids, phosphatidylcholine and phosphatidylglycerol in spleen and phosphatidylcholine in thymus. Fatty acid analysis showed a marked alteration of unsaturated fatty acids/saturated fatty acids in spleen and thymus leading to immune impairment via the fatty acid remodeling pathway. Our present in vitro lipid metabolic labeling study could open up new vistas for exploring LPS-induced immune impairment in spleen and thymus, as well as the underlying mechanism.

Effect of composition on thermoelectric properties of polycrystalline CrSi2

Ingots with compositions CrSi2-x (with 0 < x < 0.1) were synthesized by vacuum arc melting followed by uniaxial hot pressing for densification. This paper reports the temperature and composition dependence of the electrical resistivity, Seebeck coefficient, and thermal conductivity of CrSi2-x samples in the temperature range of 300 K to 800 K. The silicon-deficient samples exhibited substantial reductions in resistivity and Seebeck coefficient over the measured temperature range due to the formation of metallic secondary CrSi phase embedded in the CrSi2 matrix phase. The thermal conductivity was seen to exhibit a U-shaped curve with respect to x, exhibiting a minimum value at the composition of x = 0.04. However, the limit of the homogeneity range of CrSi2 suppresses any further decrease of the lattice thermal conductivity. As a consequence, the maximum figure of merit of ZT = 0.1 is obtained at 650 K for CrSi1.98.

Some studies on evaluation of degradation in composite adhesive joints using ultrasonic techniques

Experimental and theoretical studies on degradation of composite-epoxy adhesive joints were carried out on samples having different interfacial and cohesive properties. Oblique incidence ultrasonic inspection of bonded joints revealed that degradation in the adhesive can be measured by significant variation in reflection amplitude as also by a shift in the minima of reflection spectrum. It was observed that severe degradation of the adhesive leads to failure dominated by interfacial mode. Through this investigation it is demonstrated that a correlation exists between the bond strength and a frequency shift in reflection minimum. The experimental data was validated using analytical models. Though both bulk adhesive degradation and interfacial degradation influences the shift in spectrum minimum, the contribution of the latter was found to be significant. An inversion algorithm was used to determine the interfacial transverse stiffness using the experimental oblique reflection spectrum. The spectrum shift was found to depend on the value of interfacial transverse stiffness using which a qualitative assessment can be made on the integrity of the joint.

Composition, structure and electrical properties of DC reactive magnetron sputtered Al2O3 thin films

Thin films of alumina (Al2O3) were deposited over Si < 1 0 0 > substrates at room temperature at an oxygen gas pressure of 0.03 Pa and sputtering power of 60 W using DC reactive magnetron sputtering. The composition of the as-deposited film was analyzed by X-ray photoelectron spectroscopy and the O/Al atomic ratio was found to be 1.72. The films were then annealed in vacuum to 350, 550 and 750 degrees C and X-ray diffraction results revealed that both as-deposited and post deposition annealed films were amorphous. The surface morphology and topography of the films was studied using scanning electron microscopy and atomic force microscopy, respectively. A progressive decrease in the root mean square (RMS) roughness of the films from 1.53 nm to 0.7 nm was observed with increase in the annealing temperature. Al-Al2O3-Al thin film capacitors were then fabricated on p-type Si < 1 0 0 > substrate to study the effect of temperature and frequency on the dielectric property of the films and the results are discussed.

Cyclodextrin-functionalized Fe3O4@TiO2: reusable, magnetic nanoparticles for photocatalytic degradation of endocrine-disrupting chemicals in water supplies

Water-dispersible, photocatalytic Fe3O4@TiO2 core shell magnetic nanoparticles have been prepared by anchoring cyclodextrin cavities to the TiO2 shell, and their ability to capture and photocatalytically destroy endocrine-disrupting chemicals, bisphenol A and dibutyl phthalate, present in water, has been demonstrated. The functionalized nanoparticles can be magnetically separated from the dispersion after photocatalysis and hence reused. Each component of the cyclodextrin-functionalized Fe3O4@TiO2 core shell nanoparticle has a crucial role in its functioning. The tethered cyclodextrins are responsible for the aqueous dispersibility of the nanoparticles and their hydrophobic cavities for the capture of the organic pollutants that may be present in water samples. The amorphous TiO2 shell is the photocatalyst for the degradation and mineralization of the organics, bisphenol A and dibutyl phthalate, under UV illumination, and the magnetism associated with the 9 nm crystalline Fe3O4 core allows for the magnetic separation from the dispersion once photocatalytic degradation is complete. An attractive feature of these ``capture and destroy'' nanomaterials is that they may be completely removed from the dispersion and reused with little or no loss of catalytic activity.

Metal doped nanosized titania used for the photocatalytic degradation of rhodamine B dye under visible-light

Metal-doped anatase nanosized titania photocatalysts were successfully synthesized using a sal gel process. Different amounts of the dopants (0.2, 0.4, 0.6, 0.8 and 1.0%) of the metals (Ag, Ni, Co and Pd) were utilized. The UV-Vis spectra (solid state diffuse reflectance spectra) of the doped nanoparticles exhibited a red shift in the absorption edge as a result of metal doping. The metal-doped nanoparticles were investigated for their photocatalytic activity under visible-light irradiation using Rhodamine B (Rh B) as a control pollutant. The results obtained indicate that the metal-doped titania had the highest activity at 0.4% metal loading. The kinetic models revealed that the photodegradation of Rh B followed a pseudo first order reaction. From ion chromatography (IC) analysis the degradation by-products Rhodamine B fragments were found to be acetate, chloride, nitrite, carbonate and nitrate ions.