Screening method for nitroaromatic compounds in water based on solid-phase microextraction and infrared spectroscopy

A new method is described for determining nitroaromatic compounds in water that combines solid-phase microextraction (SPME) and infrared (IR) spectroscopy. In this method, the compounds are extracted from a 250-mL volume of water into a small square (3.2 cm x 3.2 cm x 61.2 microm thick) of silicone polycarbonate copolymer film (MEM-213). Five nitroaromatic compounds, including 2,4,6-trinitrotoluene (TNT), were chosen to evaluate the SPME/IR procedure. Quantitation limits for the five test compounds range from 50 microg/L for TNT to 400 microg/L for nitrobenzene. Precision values, determined at aqueous concentrations of four times the quantitation limit, range from 4 to 7%, and linear dynamic ranges extend to the maximum limit of the IR instrumentation. The potential of this SPME/IR method for determining nitroaromatics in natural water samples was also investigated by extracting "real world" soil samples contaminated with TNT. Results obtained from the SPME/ IR determination of the diluted extracts were in reasonable agreement with those obtained from dichloromethane extraction followed by gas chromatographic analysis.     

Bioactivity and metabolism of trans-resveratrol orally administered to Wistar rats

The purpose of this study was to investigate the implications of selected chemopreventive parameters and metabolic conversion of resveratrol in vivo. In two 8-week long feeding experiments with rats, a low-resveratrol diet containing 50 mg resveratrol per kg body weight (bw) and day and a high-resveratrol diet with 300 mg per kg bw and day were administered. For chemopreventive evaluation selected phase I and phase II enzymes of the biotransformation system, the total antioxidant activity, and the vitamin E status of the animals were determined. The level of resveratrol and its metabolites in the feces, urine, plasma, liver, and kidneys was identified and quantitated by high-performance liquid chromatography-diode array detection (HPLC-DAD) using synthesized resveratrol conjugate standards. Feeding of different dosages of resveratrol revealed no effect on the different chemopreventive parameters, except for the total antioxidant activity, which was elevated in plasma by 19% after feeding 50 mg resveratrol per kg bw and day. The formation of trans-resveratrol-3-sulfate, trans-resveratrol-4'-sulfate, trans-resveratrol-3,5-disulfate, trans-resveratrol-3,4'-disulfate, trans-resveratrol-3,4',5-trisulfate, trans-resveratrol-3-O-beta-D-glucuronide, and resveratrol aglycone was detected by HPLC analysis, depending on the biological material. Total resveratrol recovery in urine and feces of rats fed on 50 mg resveratrol per kg bw and day was 15% and 13%, respectively. For rats fed the higher dosage of 300 mg resveratrol per kg bw and day recovery was 54% and 17%, respectively. This is the first study performed with synthesized standards of relevant resveratrol conjugates. The lack of effect on the chemopreventive parameters is probably due to the formation of various resveratrol conjugates reducing its bioavailability in the rat.     

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Automated Microscale His‐tagged Protein Purification Using Ni‐NTA Magnetic Agarose Beads

To achieve standardized and parallelized microscale protein purification, an automated purification system was developed and optimized using a pipetting robot for purifying large sets of proteins with Ni‐NTA magnetic agarose beads. Recombinant hexahistidine‐tagged proteins β‐glucanase (Bgl‐His) and esterase I of Pseudomonas fluorescens (PFE I) were tested on the system. High purity along with high coherence was achieved. The purification procedure can be applied to 96 samples simultaneously and only takes about 1/3 of the time required for purification conducted by hand. Due to the stability of the robot system, the consistency of the results is much better than the results achieved through manual purification. This rapid and reliable method is reproducible and applicable to high throughput screening of huge amounts of samples.     

Structure and morphology of linear polyethylene extrudates induced by elongational flow

This study focuses on the structure, morphology, and properties of linear polyethylene (PE) profiles manufactured by continuous extrusion. High level of chain orientation was achieved using specific flow and processing conditions. An extrusion die with semihyperbolic convergency was used to generate high percentage of elongational flow and chain extension. Simultaneously, high extrusion pressure and relatively low melt temperature led to flow‐induced crystallization of PE extended chains. The structure of PE tapes consists of crystal aggregates with different level of orientation and crystallinity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development of a qualitative test method for the cleanability of polymer woven filter media

In this paper a new method for cleaning of filter media is presented, and the cleanability with different textures and surface finishes is compared. With the method described, it is possible to evaluate the quality of the cleaning process. According to the German VDMA standard cleaning test, riboflavin and malt extract are applied as model contaminants for evaluation of the cleaning results. To compare the cleanability of filter media with different properties and geometries the results are adapted to the law of mass transfer and to the Sherwood number, a dimensionless parameter describing the quality of a cleaning process.