Analysis using size exclusion chromatography of poly(N-isopropyl acrylamide) using methanol as an eluent

Size Exclusion Chromatography is traditionally carried out in either aqueous or non-polar solvents. A system to present molar mass distributions of polymers using methanol as a mobile phase is presented. This is shown to be a suitable system for determining the molar mass distributions poly(N-isopropylacrylamide)s (PNIPAM); a polymer class that is often difficult to analyze by size exclusion chromatography. DOSY NMR was used to provide intrinsic viscosity data that was used in conjunction with a viscometric detector to provide absolute calibration. Then the utility of the system was shown by providing the absolute molar mass distributions of dispersed highly branched PNIPAM with biologically functional end groups.

Effect of residual monomer from polyacrylamide on head lettuce grown in peat substrate

The paper investigates the migration of the acrylamide monomer (AMD) to lettuce chosen as a test plant growing in an organic medium (peat substrate). Polyacrylamide (PAM)-based flocculant added to the growing medium contained no more than 1000 mg kg(-1) of AMD. Plants were grown with varied doses of PAM preparation (0.5-3.0 mg dm(-3) of peat substrate) to compare the results with the control sample. The determination of AMD content, chlorophyll content, weight of the lettuce head, and also analysis of macro- and micro-elements in lyophilised test material was made under the same analytical conditions. The results showed that lettuce plants absorb AMD to the leaves from the peat substrate. The AMD uptake has a negative impact on the growth of lettuce. It reduces the average fresh weight of heads and destabilises the mineral composition of the plant. Therefore, concern related to the transfer risk of the residual AMD from sludge used for organic fertilisation of edible plants still remains a crucial question from a food and consumer safety point of view. To ensure consumer safety, the fate of the AMD following the application of PAM to cropland should be carefully monitored in the whole food chain.

Evaluation of extractables in processed and unprocessed polymer materials used for pharmaceutical applications

Polymeric materials are often used in pharmaceutical packaging, delivery systems, and manufacturing components. There is continued concern that chemical entities from polymeric components may leach into various dosage forms, particularly those that are comprised of liquids such as parenterals, injectables, ophthalmics, and inhalation products. In some cases, polymeric components are subjected to routine extractables testing as a control measure. To reduce the risk of discovering leachables during stability studies late in the development process, or components that may fail extractables release criteria, it is proposed that extractables testing on polymer resins may be useful as a screening tool. Two studies have been performed to evaluate whether the extractables profile generated from a polymer resin is representative of the extractables profile of components made from that same resin. The ELSIE Consortium pilot program examined polyvinyl chloride and polyethylene, and another study evaluated polypropylene and a copolymer of polycarbonate and acrylonitrile butadiene styrene. The test materials were comprised of polymer resin and processed resin or molded components. Volatile, semi-volatile, and nonvolatile chemical profiles were evaluated after headspace sampling and extraction with solvents of varying polarity and pH. The findings from these studies indicate that there may or may not be differences between extractables profiles obtained from resins and processed forms of the resin depending on the type of material, the compounds of interest, and extraction conditions used. Extractables testing of polymer resins is useful for material screening and in certain situations may replace routine component testing.

Antiscalant removal in accelerated desupersaturation of RO concentrate via chemically-enhanced seeded precipitation (CESP)

An experimental study was carried out to demonstrate and quantify the feasibility of antiscalant (AS) removal from brackish water RO concentrate of high gypsum scaling propensity via lime treatment prior to seeded gypsum precipitation. Based on studies with model solutions, it was shown that sufficient AS removal (up to ∼90%) from RO concentrate is feasible via a lime treatment step (at a dose significantly lower than that required for conventional lime softening) to enable effective subsequent seeded gypsum precipitation. This two-step chemically-enhanced seeded precipitation (CESP) treatment of primary RO concentrate is suitable as an intermediate concentrate demineralization (ICD) stage for high recovery desalting employing secondary RO desalination. Analysis of gypsum precipitation and lime treatment kinetic data suggests that, after adequate CaCO(3) precipitation has been induced for effective AS scavenging, CaSO(4) desupersaturation can be achieved via seeded gypsum precipitation without retardation due to seed poisoning by AS. Also, the lime dose required to prevent seed poisoning during subsequent gypsum desupersaturation via seeded gypsum precipitation can be adequately assessed with a precipitation kinetics model that considers AS seed poisoning based on a Langmuir adsorption isotherm. The degree of AS removal after lime treatment increased linearly with the logarithm of the single lime dose additions. Staged lime dosing (i.e., multiple lime additions), however, removed a higher degree of AS relative to an equivalent single lime dose addition since a higher driving force for CaCO(3) precipitation could be maintained over the course of the lime treatment period.

Isotherm and kinetic behavior of adsorption of anion polyacrylamide (APAM) from aqueous solution using two kinds of PVDF UF membranes

To determine the isotherm parameters and kinetic parameters of adsorption of anion polyacrylamide (APAM) from aqueous solution on PVDF ultrafiltration membrane (PM) and modified PVDF ultrafiltration membrane (MPM) is important in understanding the adsorption mechanism of ultrafiltration processes. Effect of variables including adsorption time, initial solution concentration, and temperature were investigated. The Redlich-Peterson equation of the five different isotherm models we chose was the most fitted model, and the R(2) was 0.9487, 0.9765 for PM and MPM, respectively; while, the pseudo-first-order model was the best choice among all the four kinetic models to describe the adsorption behavior of APAM onto membranes, suggesting that the adsorption mechanism was a chemical and physical combined adsorption on heterogeneous surface. The thermodynamic parameters were also calculated from the temperature dependence (Δ(r)G(m)(θ), Δ(r)H(m)(θ), Δ(r)S(m)(θ)), which showed that the process of adsorption is not spontaneous but endothermic process and high temperature favors the adsorption.

Preparation and Properties of Thermoresponsive Bioconjugates of Trypsin

Covalent attachment of enzymes and other proteins to the smart polymer, poly(N-isopropylacrylamide) [poly (NIPAAm)], has been widely used as a method for the preparation of thermosensitive protein conjugates. In the present study, reversible soluble-insoluble polymer-enzyme conjugates were prepared by conjugating a copolymer of NIPAAm with 5-mol % of 6-acrylaminohexanoic acid to trypsin by the carbodiimide-NHS (N-hydroxysuccinimide) coupling method. Four bioconjugates with different units of enzyme coupled to the matrix were prepared. Increased enzymatic activity in terms of high effectiveness factor (in the range of 3-5) was found in the conjugates. Kinetic parameters for the immobilized and free enzyme were determined. The Vmax/Km value of the enzyme significantly increased on immobilization by the factors in the range of 12-28. The immobilized enzyme also showed stability to autolysis at 50 degrees C.

Report: recycling of flame-retarded plastics from waste electric and electronic equipment (WEEE)

Shredder residues produced in plants processing waste electric and electronic equipment are excluded from material recycling due to a variety of polymeric materials and the presence of brominated flame retardants (BFR), which might contain banned polybrominated diphenyl ethers or toxic polybrominated dioxins and furans (PBDD/F). Herein we present a technological approach to transfer a significant portion of the shredder residue into recycled polymers. The technological approach consists of a density-based enrichment of styrenics, which are subjected to a solvolysis process (CreaSolv process) in a second stage. This stage allows the elimination of non-target polymers and extraction of BFR and PBDD/F. Pilot processing of 11.5 and 50 kg shredder residues indicated a material yield of about 50% in the density stage and 70-80% in the CreaSolv process, and an effective removal of BFR additives. The recycled products were proved to comply with threshold values defined by the European directive on the restriction of hazardous substances (RoHS) and the German Chemikalienverbotsverordnung. Mechanical material properties exhibited high tensile and flexural modules as well as slight impact strength, which qualify the products for applications in new electronic equipment.

Large-scale preparation and purification of polyacrylamide-free RNA oligonucleotides

We present a fast and simple protocol for large-scale preparation and purification of RNA oligonucleotides. RNA oligonucleotides are prepared by in vitro transcription with T7 RNA polymerase from linearized plasmid DNA templates constructed by PCR. In place of denaturing polyacrylamide gel electrophoresis (PAGE), size-exclusion chromatography is employed to purify the RNA oligonucleotide from the transcription mixture yielding >99% pure RNA product. In contrast to PAGE-based purification, the gel filtration method does not require denaturation of the RNA oligonucleotide, which is desirable for larger RNAs, and the product is free of low-molecular-weight acrylamide contaminants, which greatly benefits NMR, crystallographic, and other biophysical studies of large RNAs and RNA-protein complexes.

[The tissue reaction to acrylic plastics modified by supercritical extraction with carbon dioxide]

The process of extraction of admixtures from acryl plastic widely used in dentistry by means of supercritical carbon dioxide (sc-CO2) was studied and effects of extraction conditions on biocompatibility and toxicity of resultant materials assessed, sc-CO2 effectively purified the specimens from toxic compounds (monomers and low-molecular oligomers, methylmethacrylate, dichloroethane) and notably improved the biocompatability of polymer implants. Tissue reaction to ethacryl and protacryl depends on the degree of implant polymerization and duration of extraction of toxic substances from polymer.

Using light scattering to locate less than a microgram of protein per band in polyacrylamide tube gels after isoelectric focusing

After separation by isoelectric focusing (IEF) or non-equilibrium pH gradient electrophoresis (NEPHGE) in 9.2 M urea polyacrylamide tube gels, proteins with Mr > 20,000 can be precipitated by shaking the gels in 25% methanol. When a fiber-optic illuminator is placed in contact with the end of the gel, the cylindrical gel transmits light by internal reflection. In regions of the gel where protein is precipitated, this light is scattered, making it visible when the gel is viewed in a darkened room against a black background. The sensitivity of the method is moderate: less than 1 microgram protein per band (in a 3-mm diameter gel) can be detected. Because the protein in the bands precipitates rapidly (30 min), the solution used (25% methanol) is fairly benign to proteins, and the apparatus is not expensive, this technique should be useful in several situations including electrophoretic purification schemes. This method is especially useful for evaluating the quality of an IEF or NEPHGE tube gel before using it for the second dimension of a two-dimensional gel.

Allergic contact dermatitis to artificial fingernails prepared from UV light-cured acrylates

BACKGROUND

Contact dermatitis from artificial nails made from self-curing acrylic resins is occasionally reported. Recently, UV light-cured products introducing new acrylics have become available.

OBJECTIVE

Our purpose was to identify relevant allergens in commercial light-curing products by patch tests and to evaluate the efficacy of "hypoallergenic" products by inclusion into the test series.

METHODS

Patients wearing photobonded acrylic nails who had perionychial and subonychial eczema were patch tested with an acrylate battery and "hypoallergenic" commercial products.

RESULTS

Triethyleneglycol dimethacrylate, hydroxyfunctional methacrylates, and (meth)-acrylated urethanes proved to be relevant allergens in photobonded nail preparations. Methacrylated epoxy resin sensitization was not observed. All "hypoallergenic" products provoked positive reactions.

CONCLUSION

The omission of irritant methacrylic acid in UV-curable products does not reduce the high sensitizing potential of new acrylates. In contrast to the manufacturers' declarations, all "hypoallergenic" products continue to include acrylate functional monomers and therefore continue to cause allergic sensitization.

'Laterally aggregated' polyacrylamide gels for electrophoresis

A new method is described for producing highly porous polyacrylamide matrices: polymerization in presence of a preformed hydrophilic polymer. If a standard mixture of monomers (e.g., 5%T, 4%C) is polymerized in presence of, e.g., polyethylene glycol (PEG) 10 kDa, lateral chain aggregation occurs, with formation of large pore sizes. In PEG 10 kDa, the transition from a small- to a large-pore gel is clearly apparent at 0.5% PEG addition and reaches a plateau already at 2.5% PEG. Even with shorter PEG fragments (6.2 and 1 kDa) this transition occurs, but with progressively larger amounts of PEG in solution (up to 25% for the 1 kDa species). Other polymers such as hydroxymethyl cellulose (1000 kDa) and polyvinyl-pyrrolidone (360 kDa and 25 kDa) are also able to elicit this phenomenon. It appears that lateral chain aggregation (before the cross-linking event) is induced via intra-chain hydrogen bonding, since urea and temperature strongly inhibit it, whereas tetramethylurea (an agent quenching hydrophobic interactions) does not hamper it. By scanning electron microscope, it is found that the maximum pore size obtained in a 5%T, 4%C gel in presence of 2.5% PEG 10 kDA is of the order of 0.5 micron, whereas the same 5%T, 4%C control gel would have an average pore diameter of 5 nm. Thus, an increment of pore size of about 2 orders of magnitude is obtained: in these new matrices, a 21000 bp DNA fragment exhibits a much greater migration than in a control gel in which the sample is entrapped at the application site.