A biostimulation-based accelerated method for evaluating the biodegradability of polymers

The high cost and long duration of the existing standard tests, such as ASTM D5338 and ISO 14855, represents an important drawback in evaluating the biodegradability of polymers. This works presents a new accelerated method for this purpose, based on the use of a Bartha respirometer and biostimulation with yeast extract. The new method was applied to microcrystalline cellulose (MCC), low density polyethylene (LDPE), poly(3-hidroxybutyrate) (PHB), poly(lactic acid) (PLA), poly(vinyl alcohol) (PVOH), polypropylene (PP) and poly(ethylene terephthalate) (PET). The results obtained with these polymers were consistent with those of the standard methods in terms of differentiating biodegradable and non-biodegradable polymers and relative order of biodegradation extent. Besides, a significant reduction of test duration was achieved (from 45 to 110 days with ASTM D5338 or ISO 14855 to 28 days). These results corroborate the potential of the proposed method as a fast test for assessment of biodegradation of polymeric materials.     

A fast way of solving Jonah and coworkers' equations to evaluate anisotropic-isotropic transition temperatures of semirigid polymers

A fast and simple method has been found to solve the set of equations recently proposed by Jonah, Brostow and Hess [Macromolecules 26 , 76 (1993)], allowing the evaluation of the anisotropic-isotropic transition temperature for a semirigid liquid polymer. Starting with given values of η (average length of the rigid sequences coexisting with flexible sequences inside the semiflexible polymer chains) and θ (degree of rigidity of the semirigid polymer), a reduced transition temperature τ is readily obtained, together with the transition values of the anisotropic order parameters s and γ.     

A fast and simple high-performance liquid chromatographic assay for aryl hydrocarbon hydroxylase

A simple high-performance liquid chromatographic method using fluorescence detection of the remaining substrate is described for the determination of benzo[alpha]pyrene hydroxylase activity. This assay is far simpler than the previous ones, as it does not require extraction or centrifugation and the measurement occurs directly after dilution of the total incubation medium. The aryl hydrocarbon hydroxylase (AHH) activities in rat liver microsomes are in agreement with those obtained by radioactive assays. Moreover, this assay allows the routine determination of the AHH activity in animal tissues.     

A fast, simple, and reliable hydrophilic interaction liquid chromatography method for the determination of ascorbic and isoascorbic acids

A reliable method for the determination of total vitamin C must be able to resolve ascorbic acid (AA) and the epimeric isoascorbic acid (IAA) and determine the sum of AA and its oxidized form dehydroascorbic acid. AA and IAA are polar molecules with a low retention time in conventional reversed phase systems, and hence of difficult resolution. Hydrophilic interaction chromatography using a TSKgel Amide-80 stationary phase with isocratic elution was successful in resolving the two epimers. The column was compatible with injections of high concentrations of metaphosphoric acid, tris(2-carboxyethyl)-phosphine, and EDTA without drift of baseline and retention time. Total AA and IAA were extracted, stabilized, and reduced in one step at 40 °C, using 5% m-phosphoric acid, 2 mM of EDTA, and 2 mM of tris(2-carboxyethyl)-phosphine as reducing agent. This simple, fast, and robust hydrophilic interaction chromatography-DAD method was applied for the analysis of food products namely fruit juices, chestnut, and ham and also in pharmaceutical and multivitamin tablets. Method validation was performed on the food products, including parameters of precision, accuracy, linearity, limit of detection, and quantification (LOQ). The absence of matrix interferences was assessed by the standard addition method and Youden calibration. The method was fast, accurate, and precise with a LOQ_AA of 1.5 mg/L and LOQ_IAA of 3.7 mg/L. The simple experimental procedure, completed in 1 h, the possibility of using IAA as an internal standard, and low probability of artifacts are the major advantages of the proposed method for the routine determination of these compounds in a large number of samples.     

A fast and simple method for the estimation of natural uranium in urine

Natural uranium (U) in urine was co-precipitated with Ca₃(PO₄)₂ and then with BiPO₄ after reducing uranyl ions from +6 to +4 state. U separated from BiPO₄ was then quantified by measuring its absorbance after complexing it with Arsenazo-III. The interference caused by ions such as Fe³⁺, Bi³⁺, Zn²⁺ and PO₄ ³⁻ was studied during the measurement of U absorbance. The percent recovery of U was 81.4±2.6 for 5 to 30 μg U present in 500 ml urine. The minimum detectable concentration of U was 2 μg/l and the time required to complete the analysis was 2 days.     

Integral equation theory for athermal solutions of linear polymers

An integral equation model is developed for athermal solutions of flexible linear polymers with particular reference to good solvent conditions. Results from scaling theory are used in formulating form factors for describing the single chain structure, and the impact of solvent quality on the chain fractal dimension is accounted for. Calculations are performed within the stringlike implementation of the polymer reference interaction site model with blobs (as opposed to complete chains) treated as the constituent structural units for semidilute solutions. Results are presented for the second virial coefficient between polymer coils and the osmotic compressibility as functions of the chain length and polymer volume fraction, respectively. Findings from this model agree with results from scaling theory and experimental measurements, as well as with an earlier investigation in which self-avoiding chains were described using Gaussian form factors with a chain length and concentration-dependent effective statistical segment length. The volume fractions at the threshold for connectedness percolation are evaluated within a coarse-grained closure relation for the connectedness Ornstein-Zernike equation. Results from these calculations are consistent with the usual interpretation of the semidilute crossover concentration for model solutions of both ideal and swollen polymer coils.     

A fast and simple method for background removal in Auger electron spectroscopy

A purely formal method for background removal in electron beam induced Auger electron spectroscopy is presented. The method has been developed for practical purposes. It is typically used to remove the background of a complete recorded spectrum, no fit is necessary to remove the backscattered electrons background. An overcompensation of the background, resulting in negative values of the background removed spectrum is not possible, all values of the background removed spectrum are positive or zero. Since the Auger peaks are separated by zeros after background removal, the method is well suited for peak finding and identification.     

A fast and simple method for background removal in Auger electron spectroscopy

A purely formal method for background removal in electron beam induced Auger electron spectroscopy is presented. The method has been developed for practical purposes. It is typically used to remove the background of a complete recorded spectrum, no fit is necessary to remove the backscattered electrons background. An overcompensation of the background, resulting in negative values of the background removed spectrum is not possible, all values of the background removed spectrum are positive or zero. Since the Auger peaks are separated by zeros after background removal, the method is well suited for peak finding and identification.Dedicated to Professor Dr. H. Seiler on the occasion of his 65th birthday     

A simple strategy for detecting synthetic polymers on solid surfaces using liquid crystal

In this study, we developed a liquid crystal (LC)-based detection method for polymer films synthesized on solid surfaces. A dark to bright transition in the optical appearance of nematic 4-cyano-4′-pentylbiphenyl (5CB) was observed after transferring a poly(methyl methacrylate) (PMMA) film onto a glass substrate functionalized with n-octyltrichlorosilane (OTS). This phenomenon indicates an orientational transition of 5CB from a homeotropic to a planar-random state. The optical response of 5CB was then evaluated directly through polymerization reactions on the OTS-functionalized glass substrate. Polymer films of PMMA, poly(glycidyl methacrylate) (PGMA), and poly(dimethylsiloxane) (PDMS) were synthesized on OTS surfaces covered with their reaction mixtures. All polymer films displayed bright signals of 5CB, which corresponded to the planar-random orientation of LCs. However, no change in orientation was observed for the control experiments. We confirmed the formation of polymer films on the OTS surface using atomic force microscopy. Overall, our results suggest that LCs can be used to construct optical monitoring systems for the product of polymerization reactions.

A simple and fast sampling method for the characterization of volatile compounds released byNezara viridula

Summary A simple method is described for the collection of volatile compounds from a biological matrix and for their subsequent GC-MS analysis. (E)-2-decenal and (E)-2-decenyl acetate odorous compounds from bugs of theNezara viridula species were detected together with n-dodecane and n-tridecane hydrocarbons as carriers. The chemical composition of the secretions of the bugs collected in the Veneto region corresponds to one obtained from the same American pentatomidae.     

A simple,fast and convenient new method for predicting the stability of nitro compounds

Journal of Computer-Aided Molecular Design - A new method has been proposed to understand and predict the stability of nitro compounds. This method uses the maximum electron densities at the...     

A fast isocratic liquid chromatography method for the quantification of xanthophylls and their stereoisomers

A fast isocratic liquid chromatography method was developed for the simultaneous quantification of eight xanthophylls (13‐Z‐lutein, 13’‐Z‐lutein, 13‐Z‐zeaxanthin, all‐E‐lutein, all‐E‐zeaxanthin, all‐E‐canthaxanthin, all‐E‐β‐apo‐8’‐carotenoic acid ethyl ester and all‐E‐β‐apo‐8’‐carotenal) within 12 min, compared to 90 min by the conventional high‐performance liquid chromatography method. The separation was achieved on a YMC C₃₀ reversed‐phase column (100 mm x 2.0 mm; 3 μm) operated at 20°C using a methanol/tert‐butyl methyl ether/water solvent system at a flow rate of 0.8 mL/min. The method was successfully applied to quantify lutein and zeaxanthin stereoisomers in egg yolk, raw and cooked spinach, and a dietary supplement. The method can be used for the rapid analysis of xanthophyll isomers in different food products and for quality control purposes.     

A simple and rapid method for determination of boron in fast breeder reactor components

The present paper describes a new analytical method developed for direct determination of boron in steels using radio frequency glow discharge optical emission spectrometer. “Single parameter alternative method” technique has been used to optimize the various experimental conditions of glow discharge plasma such as forward power, gas pressure inside plasma chamber, pre-integration time, and integration time. Different emission lines for boron were studied and inter element interference effect is also discussed in the paper. A complete statistical analysis has been done to validate the developed method. A RSD of less than ±5% is achieved for boron in the range of 0.0010–0.020% in Steels using this method.     

A simple model for finitely extensible polymers

A simple model for the calculation of configurational and rheological properties of finitely extensible polymers in flow is introduced. The finite extensibility of the chain is incorporated into the common Rouse model by varying the spring constant such that a constant contour length is maintained for every flow strength. For elongational flow, a comparison with Monte Carlo simulations of a bead-rod chain with 100 links yields qualitative agreement. For shear flow, this model predicts non-Newtonian flow behaviour.     

A simple method suitable to test the ultimate biodegradability of environmentally degradable polymers

A straightforward experimental set-up derived from the Biometer Flask previously utilized for experiments of pesticides biodegradation, has been adopted for testing the ultimate biodegradability of natural, synthetic and semi-synthetic polymeric materials on solid substrates such as soil and mature compost. The use of these whole substrates as incubation media in respirometric experiments, may negatively affect the accuracy of the test due to the large amount of carbon dioxide developed from the blanks, especially in the presence of specimen degrading at low or moderate rates. In the present test procedure soil and compost samples are diluted with perlite, a naturally occurring inert aluminum silicate widely utilized in horticultural applications, in order to ensure optimal conditions for the microbial growth while reducing the carbon dioxide emissions from the blanks. The results so far reported clearly indicate that the adopted procedure is extremely valuable and versatile for the appreciation of even subtle differences in the biodegradation rate of different polymeric materials, as well as for long-term degradation experiments.     

A simple method of evaluating non-isothermal crystallization kinetics in multicomponent polymer systems

A new simple method of evaluating non-isothermal crystallization kinetics is proposed. The procedure based on mathematical treatment of DSC cumulative crystallization curves at their inflection point provides three kinetic parameters: temperature of start of crystallization (T_s), temperature of maximum crystallization rate (T_i) and numerical value of the maximum crystallization rate (s_i), and also final crystallinity after cooling (CR_c). The method is demonstrated on the system poly(ɛ-caprolactone)/poly(lactic acid)/clay C15 and related microfibrillar composite. The method provides the values of T_s and T_i with standard deviation σ = 0.3 and 0.4 °C, respectively. The coefficient of variation v of s_i and CR_c is 5.8 and 1.5%, respectively. The proposed method does not refer to any crystallization model and does not require exact determination of the starting time. It is particularly useful for characterizing a series of samples derived by modification of the neat polymer.     

A simple,fast method for the analysis of 20 contaminants of emerging concern in river water using large-volume direct injection liquid chromatography-tandem mass spectrometry

Analytical and Bioanalytical Chemistry - A fast and sensitive method for the determination of a structurally and physico-chemically diverse group of contaminants of emerging concern (CEC) based on...     

A simple and fast method for the determination of active ingredient in antiperspirant cosmetics by neutron activation analysis

Antiperspirant cosmetics are tested for their active ingredient (aluminium chlorohydroxide) by conventional analytical techniques. Aluminium has been determined by instrumental neutron activation analysis in all antiperspirant products and package forms available in the Greek market in order to develop a simple and fast method for its quantitation. Our results show that neutron activation analysis could be established as an official method for the determination of active ingredient in antiperspirant cosmetics. The proposed method is compared with the existing official methods and an alternative sampling method for aerosol package is presented.     

Rapid method for evaluating reversed-phase high-performance liquid chromatography column stability

A procedure is presented for the rapid evaluation of HPLC stationary phase stability at pH 8.4 or 10.1 using a temperature of 60 degrees C. Mobile phase (MeOH-0.1 mol l(-1) aqueous NaHCO3, 50:50, v/v) is continuously passed through the column with periodic injections of a test solution until the several chromatographic parameters of the resulting chromatograms are degraded. The tests were applied to several commercial and laboratory-made stationary phases. After degradation two of these phases, one commercial and one laboratory-made, were examined by elemental analysis and scanning electron microscopy to elucidate the degradation process.