Determination of hydrazine in polyvinylpyrrolidone by derivatization and square wave voltammetry

A rapid and precise method has been developed for the determination of hydrazine in polyvinylpyrrolidone (PVP). Hydrazine is converted to salicylaldazine by reaction with salicylaldehyde. After extraction, the azine is reduced at –1.56 V versus the SCE at the hanging drop electrode. Detection is accomplished using square wave voltammetry and comparison to an external salicylaldazine standard. The described procedure can detect as little as 70 ng/g hydrazine in PVP.     

Turbidimetric determination of sulphate in waters employing flow injection and lead sulphate formation

An analytical flow-injection procedure based on PbSO₄ colloidal formation is proposed as a turbidimetric determination of sulphate in natural waters. Ethanol-water was used as a medium in order to improve the sensibility of the method. Both chemical and flow variables as well as interfering species were studied. A detection limit of 0.3 μg SO²⁻₄ ml⁻¹ was found, and the analytical range (according to Beer's law) was 2–20 μg SO²⁻₄ ml⁻¹. The precision was better than 3% R.S.D. and the sample throughput was ca. 35 h⁻¹. The method, when compared with a standard methodology, gave good results when applied to water analysis.     

Immobilized enzymes - A simple calorimetric method for the determination of the catalytic activity

The results communicated in this paper show that rapid and reliable information about the activity of immobilized enzymes follows from calorimetric measurements. The study was done using spherical and plain carriers as well as different enzymes (urease, glucose-oxidase, invertase). The enzyme thermistor developed by Danielsson et al. was used as a measuring system. This measuring system was applied to investigate the activity of enzyme carrier complexes produced by the sol-gel technique. The influence of processing parameters could be pointed out at complexes of different forms (xerogel, gel on ceramic carrier, thin gel layers on foil, etc.). With the described calorimetric method, a fast and reliable technique for comparative determination of the activity of immobilized enzymes is available. A special advantage of this method is its variability in carriers and the generally applicable thermal measuring principle. Therefore, it seems useful for the development of new immobilization techniques.     

Polypropylene–clay nanocomposite structure probed by H NMR relaxometry

In this paper, we used low-field nuclear magnetic resonance (NMR) relaxometry and X-ray diffraction techniques to characterize polypropylene and to probe the polypropylene/clay interactions in non-exfoliated and exfoliated polypropylene–clay nanocomposites. Differences in T₁H longitudinal relaxation time data and X-ray diffraction spectra were correlated with the presence of different domains in the samples studied. The results demonstrated the potential of H NMR relaxometry as a tool in the characterization of polymer–clay nanocomposites.     

Direct measurement of lithium in whole blood using microchip capillary electrophoresis with integrated conductivity detection

The direct measurement of lithium in whole blood is described. Using microchip capillary electrophoresis (CE) with defined sample loading and applying the principles of column coupling, alkali metals were determined in a drop of whole blood. Blood collected from a finger stick was mixed with anticoagulant and transferred onto the chip without extraction or removal of components. The electrokinetic transport of red blood cells inside the channels was studied to find sample loading conditions suitable for the analysis of lithium without injecting cells into the separation channel. Both bare glass chips and chips coated with polyacrylamide were used showing the behavior of the cells under different electroosmotic flow conditions. In serum a detection limit for lithium of 0.4 mmol/L was reached. Proteins quickly contaminated untreated chip surfaces but devices with coating gave reproducible electropherograms. In addition, potassium and sodium were also detected in the same separation run. To our knowledge, this is the first device to directly measure ions in whole blood with the use of capillary zone electrophoresis on a microchip.     

Spectroscopic study of the water-soluble organic matter isolated from atmospheric aerosols collected under different atmospheric conditions

The composition of the water-soluble organic matter from fine aerosols collected in a rural location during two different meteorological conditions (summer and autumn) was investigated by UV-vis, synchronous fluorescence (with Δλ = 20 nm), FT-IR and CPMAS-¹³C NMR spectroscopies. A seasonal variation in the concentration of total carbon, organic carbon and water-soluble organic carbon was confirmed, with higher values during the autumn and lower values during the summer season. The chemical characterisation of the water-soluble organic matter showed that both samples are dominated by a high content of aliphatic structures, carboxyl groups and aliphatic carbons single bonded to one oxygen or nitrogen atom. However, the autumn sample exhibits a higher aromatic content than the summer sample, plus signals due to carbons of phenol, ketones and methoxyl groups. These signals were attributed to lignin breakdown products which are likely to be released during wood combustion processes. The obtained results put into evidence the major contribution of biomass burning processes in domestic fireplaces during low temperature conditions into both the concentration and the bulk chemical properties of the WSOC from fine aerosols.     

Phytotoxic metabolites by nine species of Botryosphaeriaceae involved in grapevine dieback in Australia and identification of those produced by Diplodia mutila,Diplodia seriata,Neofusicoccum australe and Neofusicoccum luteum

Botryosphaeria dieback is one of the main trunk diseases of grapevine caused by several species of Botryosphaeriaceae. Twenty-four fungal isolates representing the eight most widespread and most virulent Botryosphaeriaceae were tested for their ability to produce phytotoxic metabolites. The chromatographic profiles of their culture filtrates organic extracts showed the ability of all isolates to produce several and different metabolites. When tested on grapevine leaves and tomato cuttings the organic extracts phytotoxicity varied among isolates and species. To our knowledge, this is the first study on phytotoxic compounds produced by Botryosphaeriaceae species found in Australian vineyards. The phytotoxic metabolites produced by Diplodia seriata, Diplodia mutila, Neofusicoccum australe and, for the first time, by Neofusicoccum luteum were isolated and chemically identified essentially by spectroscopic methods.

     

Synthesis of resistant starches in plants

The increased incidence in many countries in lifestyle diseases such as colorectal cancer, cardiovascular disease, and diabetes has led to an enhanced interest in disease-prevention measures that can be delivered to target populations through diet. Resistant starch (RS) is emerging as an important dietary component that has the potential to reduce the incidence of bowel health disorders. However, the range of crop species that can serve as effective sources of RS is limited. In this paper the state of knowledge of the starch biosynthesis pathway is reviewed and opportunities to manipulate crop genetics in order to generate additional sources of RS are discussed. The need for a "whole of chain" approach to delivery of RS to the consumer is highlighted because of the impact that different food-processing technologies can have in maintaining, enhancing, or destroying the RS potential of a raw material or food.     

Reaction of 5-aminopyrazoles with β-dimethylaminopropiophenones. Synthesis of new pyrazolo[3,4-b]pyridines

Several new pyrazolo[3,4-b]pyridines were obtained from the reaction of 5-amino-1-aryl-3-methylpyrazoles 1 with β-dimemylaminopropiophenones 2 in pyridine. The structure elucidation of 4,5-dihydropyrazolo[3,4-b]pyridines 3 is based on nmr measurements and X-ray diffraction. The treatment of compounds 3 with N-bromosuccinimide led to the formation of pyrazolo[3,4-b]pyridines 4 .     

Monosaccharides and the VO(IV) metal ion: Equilibrium,thermal studies and hypoglycemic effect

Protonation and complexation equilibriums of monosaccharides and the VO(IV) metal ion in aqueous solution were studied as well as their effect on the hyperglycemia of diabetic rats. The complexes formed were characterized by potentiometric titrations, paramagnetic resonance spectroscopy (EPR) and thermogravimetric–differential scanning calorimetry (TGA–DSC). The system involving d-gluconic acid (HGlu) and oxovanadium(IV) (VO²⁺) was chosen to study the serum glucose levels in alloxan-induced diabetic rats. A binuclear species was detected in small quantities, which was formed by coordination of two HGlu molecules and two VO²⁺ ions through a hydroxide bridge. The mononuclear species formed by HGlu and VO²⁺ were confirmed by EPR. The anisotropic spectra obtained from aqueous frozen solutions (77 K) are characteristic of mononuclear VO-hexoses. The cyclic sugars d-ribone-1,4-lactone (Riblac), d-galactone-1,4-lactone (Galac) and 2-deoxy-d-glucopyranose (dGlu) showed weak interactions with the metal ion and they are not able to hold the metal in solution above pH 4.6 resulting in hydrolysis of the metal ion. Also, the acute treatment with sugar complexes of HGlu–VO led to a significant hypoglycemic effect (23% and 18% by intraperitoneal or oral gavage treatment, respectively) in diabetic rats. These results show the potential effectiveness of VO–HGlu complexes as anti-hyperglycemic agents through intraperitoneal injection in alloxan-induced diabetic rats.