Development of a portable immunoextraction-reversed-phase liquid chromatography system for field studies of herbicide residues

A portable system based on immunoextraction and reversed-phase HPLC was developed for the field analysis of herbicides in groundwater and surface water. Atrazine, simazine, and cyanazine were used as model analytes for this work. These were measured in water by using three coupled columns: an anti-atrazine antibody column for the selective extraction of these analytes, a reversed-phase precolumn for their reconcentration, and a reversed-phase analytical column for their separation. Various factors were considered in the optimization of this system, including the binding properties of the immunoextraction column, the effect of flow rate on the performance of each column, the selection of sample volume, and the choice of mobile phases for the RPLC columns. A typical analysis with this system allowed the injection of one sample every 7.5 min and provided results for all three of the tested herbicides in less than 10 min. In the analysis of atrazine alone, samples could be injected every 4 min and results were obtained within 8 min. There was good correlation between this technique and a comparable benchtop system. The lower limits of detection for the given analytes were approximately 0.2-0.25 microg/L, with a linear range that extended to 20 microg/L and a dynamic range that went up to at least 100 microg/L. The use of this technique in the field was demonstrated through applications that involved the development of time and location profiles for triazine herbicides in environmental samples.     

Bibliography of food microbiology

The European and International Standard method for the detection of Listeria monocytogenes, described in EN ISO 11290 Part 1: 1997 (International Organisation for Standardisation, Geneva) was validated by order of the European Commission (Standards, Measurement and Testing Fourth Framework Programme Project SMT4-CT96-2098). Nineteen laboratories in 14 countries in Europe participated in a collaborative trial to determine the performance characteristics of the method, which are intended for publication in the corresponding standard. An additional objective of this project was to devise a new series of parameters to indicate the 'precision' of microbiological qualitative methods. The method was challenged with three food types, namely fresh cheese, minced beef and dried egg powder and a reference material. Inoculation levels ranged from 5 to 100 cfu/25 g. Each participant examined five replicates of each food type at three inoculum levels and five reference materials. Both PALCAM and Oxford media were assessed. All test materials were subjected to stringent homogeneity and stability testing before being used in the collaborative trial. The results demonstrated that the method prescribed in EN ISO 11290-1 had an overall sensitivity of 85.6% and a specificity of 97.4%. L. monocytogenes was detected in most cases after primary enrichment, although secondary enrichment often yielded further positives. However, a significant number of false-negative results were obtained with all food types when large numbers of L. innocua were present in the test materials. L. innocua tended to dominate L. monocytogenes during the selective enrichment stages and thus masked small numbers of colonies of L. monocytogenes on the isolation media. There was no evidence from this collaborative study to demonstrate a significant difference in performance between Oxford and PALCAM media. Due to the problem of false-negative results with this method as highlighted in this trial, recommendations have been made to ISO to launch a revision of the standard to improve the detection of low numbers of L. monocytogenes in foods. New statistical methods devised to advance the measurement of the performance of qualitative microbiological methods are also described.     

Steam oxidation and mechanical performance of a ferritic–martensitic steel with slurry aluminide coating

A key route to advancing power plant efficiency is to enhance current steam operating parameters, namely, increase in steam temperature and pressure from the current levels of 540°C and 180 bar to the proposed 700°C (EU) and 300 bar. Conventional ferritic–martensitic steels, while having good mechanical properties and fatigue resistance, do not possess the high-temperature corrosion resistance for long-term use, with a temperature limit of ~620°C. Adding aluminide coatings to the surfaces of the steels can improve the oxidation resistance of this class of material through the growth of an Al₂O₃ scale. One of the major concerns in using coating is the potential deleterious effects on the mechanical properties of the substrate, either through the precipitation of brittle phases or through cracks in the coating. This study compares the microstructural features of slurry aluminide coatings applied to Grade 91 and the change in mechanical performance. The tensile, thermomechanical fatigue and creep test results showed that while the coated samples entered the tertiary creep zone earlier than the uncoated ones, cracking of the coating remained confined to the surface of the specimen. Nanoindentation mapping showed a hardness increase in the coating and within the aluminium diffusion zone, which is related to the exposure time.     

Structural and rheological properties of kappa (κ)-carrageenans covalently modified with cationic moieties

Cationized kappa-carrageenans containing 2-hydroxy-3-(trimethylammonium)propyl groups with various degrees of substitution (0.13–0.75) were synthesized by reaction of sulfated polysaccharides with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (QUAB 188) in alkaline solutions through the generation of the corresponding 2,3-epoxy reagent in situ. The structure of the modified algal polysaccharides was characterized without any further treatment or after methanolysis and/or enzymatic depolymerization, by means of spectroscopic tools (FT-IR, NMR, Mass spectrometry) and high-performance size exclusion chromatography (HPSEC). Significant differences in the rheological properties of these cationized kappa-carrageenans have been found depending on the DS values and the presence of KCl salt. Despite their lower molecular weights in comparison with native polysaccharides, cationized kappa-carrageenans with a DS of 0.75 exhibited high viscosity and gelling behaviors mediated by the high density of quaternary ammonium groups.     

Laboratory-scale apparatus for the characterization of gas-phase dioxin adsorption

Zeolites are reported as selective adsorbents for the preconcentration of dioxin congeners for emission monitoring at stationary sources. This article involves the development of a laboratory-scale apparatus to characterize gas-phase dioxin adsorption on zeolites and thermal desorption. The laboratory-scale apparatus prepared stable levels of dioxin in a nitrogen flow and in-line adsorption/thermal desorption coupled to a gas chromatograph–mass spectrometer. The apparatus takes into account the low-volatility of the dioxins for their transport in the carrier gas and the possible high temperatures used for zeolite desorption. The apparatus functionalities, such as in-line concentration measurement by a sampling loop and gas chromatograph–mass spectrometer and breakthrough measurement during in-line adsorption, were validated. The generator delivers a stable 2,3-dichlorodibenzo-p-dioxin concentration of 304 ± 6 µg/m³ over 20 days. Two methods, weighing a vial and mass analysis of the sampling loop, were employed for measuring the concentration provided results that were in good agreement. Preliminary gas-phase adsorption experiments have been carried out without any memoryw effects in the valves and transfer lines. The dioxin concentration generated and large diameter of the beads led to low adsorption efficiency of dioxin on FAU13X Na-type zeolites due to a low micropore accessibility.     

Delayed Exercise Training Improves Obesity-Induced Chronic Kidney Disease by Activating AMPK Pathway in High-Fat Diet-Fed Mice

Exercise training is now recognized as an interesting therapeutic strategy in managing obesity and its related disorders. However, there is still a lack of knowledge about its impact on obesity-induced chronic kidney disease (CKD). Here, we investigated the effects of a delayed protocol of endurance exercise training (EET) as well as the underlying mechanism in obese mice presenting CKD. Mice fed a high-fat diet (HFD) or a low-fat diet (LFD) for 12 weeks were subsequently submitted to an 8-weeks EET protocol. Delayed treatment with EET in obese mice prevented body weight gain associated with a reduced calorie intake. EET intervention counteracted obesity-related disorders including glucose intolerance, insulin resistance, dyslipidaemia and hepatic steatosis. Moreover, our data demonstrated for the first time the beneficial effects of EET on obesity-induced CKD as evidenced by an improvement of obesity-related glomerulopathy, tubulo-interstitial fibrosis, inflammation and oxidative stress. EET also prevented renal lipid depositions in the proximal tubule. These results were associated with an improvement of the AMPK pathway by EET in renal tissue. AMPK-mediated phosphorylation of ACC and ULK-1 were particularly enhanced leading to increased fatty acid oxidation and autophagy improvement with EET in obese mice.     

Microwave and convective dehydration of ethanol treated and frozen apple – physical properties and drying kinetics

The objective of this study was to examine how the drying kinetics and physical properties of apples are affected by pre-treatment with 95% ethanol or freezing at –18 °C before microwave-assisted air dehydration at 50, 60 and 70 °C. Microwave heating was used to obtain these temperatures in the centre of the apple cubes. After dehydration the shrinkage and rehydration capacity were measured. The texture of dehydrated and rehydrated samples was analysed with a puncture test in a texture analyser. Samples were also analysed with confocal laser scanning microscopy to determine the correlation between physical and microstructural properties. Diffusivity in the different dehydration processes was calculated. Ethanol-treated apples showed both high rehydration and high effective rehydration capacity compared with the other samples. Freezing before dehydration increased the diffusivity and reduced the firmness of rehydrated apples compared with no pre-treatment.     

Adsorption of Novel Alkylaminoamide Sugar Surfactants at Tailor-made Surfaces

N,N-di(3-aminopropyl)dodecylamine (C12-Y-amine), N-dodecyl-N,N-di[(3-d-gluconylamido)propyl]amine (C12-DGA), N-dodecyl-N,N-bis[(3-lactobionylamido)propyl]amine (C12-DLA), N-dodecyl-N-[(3-lactobionylamido)propyl]amine (C12-LA), and ethoxylated N,N-di(3-aminopropyl)dodecylamine [C12-Y-amine with 4 and 8 ethylene oxide (EO)] have been synthesized, and their physical-chemical properties have been studied. Adsorption was measured at the air–water interface by the du Noüy ring method and at solid surfaces consisting of self-assembled monolayers (SAMs) of alkanethiols on gold using surface plasmon resonance. Results from surface tension measurements showed that adsorption at the air–water interface is pH dependent. At low pH, reduction in surface tension is less pronounced as a result of protonation of the amino groups of the surfactants. At the SAM model surfaces, generated by adsorption of alkanethiols or mixtures of alkanethiols on gold presenting methyl, hydroxyl, and carboxyl groups, the highest amount of adsorbed surfactant was obtained on a surface composed of a mixture of methyl and carboxyl groups. In general, the sugar-derived surfactants, DGA, DLA, and LA, adsorbed less than the ethoxylates. Surfactant biodegradation was investigated by the closed bottle test. Only C12-Y-amine was found to be readily biodegradable. However, the polyol surfactants were more biodegradable than the ethoxylates.