Rheological and transport properties of sulfonated polyacrylamide hydrogels for water shutoff in porous media

In this research, an optimal hydrogel, based on sulfonated polyacrylamide, was synthesized by statistical design of experiments using central composite method. This new hydrogel composed of sulfonated polyacrylamide (AN125VLM) and chromium triacetate as copolymer and crosslinker, respectively. The bottle and rheological tests were conducted to investigate the gelation time, thermal stability, gel strength and also ultimate elastic modulus, complex modulus, and yield stress. It was found that copolymer concentration had the main effect in both rheological and transport properties of hydrogels. The sample prepared at optimum condition, i.e. copolymer concentration of 26,340 ppm and crosslinker/copolymer ratio of 0.12, had an ultimate elastic modulus of 29.9 kPa, yield stress of 800 Pa, and complex modulus of 32 kPa. A coreflooding test through fracture was carried out to examine the optimum gel performance in a porous media. A value of 483 for the residual resistance factor ratio of water to oil confirmed the high ability of the hydrogel in reducing the relative permeability of water to oil in fractured media. Copyright © 2014 John Wiley & Sons, Ltd.     

以淀粉溶液为催化剂锅三组分法合成四氢苯并[b]吡喃和3,4-二氢吡喃并[c]苯并吡喃衍生物简

Tetrahydrobenzo[b]pyran and 3,4-dihydropyrano[c]chromene derivatives were synthesized via a one-pot three-component condensation of aromatic aldehydes with malononitrile and dimedone or 4-hydroxycoumarin in excellent yields in the presence of starch solution as a highly efficient homogenous catalyst. The use of a nontoxic and biodegradable catalyst, simple work-up procedure, and short reaction time are advantages of this method.     

Anodic stripping voltammetric determination of bismuth after solid-phase extraction using amberlite XAD-2 resin modified with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

A highly selective and sensitive anodic stripping differential pulse polarographic method has been developed for the determination of trace amount of bismuth in various samples after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex on amberlite XAD-2 resin in the pH range of 2.0-3.0. The retained analyte on the resin recovered with 10.0 ml of 2 M hydrochloric acid and bismuth is determined by anodic stripping differential pulse polarography. In this case, 0.15 μg of bismuth can be concentrated in the column from 1100 ml of aqueous sample, where its concentration is as low as 0.14 ng ml⁻¹ and the linearity is maintained in the concentration range 0.05-160 μg ml⁻¹ in final solution with a correlation coefficient of 0.999 and relative standard deviation of ±1.2%. Various parameters such as the effect of pH, flow rate, and interference of number of metal ions on the determination of bismuth have been studied in detail to optimize the conditions for determination of bismuth in standard alloys: Nippon Keikinzoku Kogyo (NKK CRM No. 916 aluminum alloy); (NKK CRM No. 1021 Al, Si, Cu, Zn alloy); and (NKK CRM No. 920 aluminum alloy), biological samples: National Institute for Environmental Studies (NIES, No. 5 human hair; NIES, No. 7 tea leaves) and water samples: (spring water, river water; Kerman water; and Shiraz water).     

Chemical Composition of the Essential Oil of Stachys inflata Benth. from Iran

The chemical composition of a hydrodistilled oil of Stachys inflata Benth. growing wild in Iran was examined by GC/MS. Thirty-nine constituents were identified. The major components of the oil were germacrene-D (16.9%), bicyclogermacrene (16.6%), -pinene (11.3%), -phellandrene (9.8%), bicycloelemene (6.6%), -pinene (5.6%), and spathulenol (3.2%).     

Sol-gel immunoaffinity chromatography for the clean up of ochratoxin A contaminated grains

This paper describes the application of sol-gel immunoaffinity columns for clean up of ochratoxin A contaminated cereal crops. Monoclonal antibodies selective for OTA have been entrapped into the pores of a sol-gel matrix in order to prepare immunoaffinity columns. Different parameters such as amount of entrapped antibodies and loading conditions were optimized to obtain highest possible recoveries of OTA. The method has been found to be a suitable tool in sample preparation prior to HPLC-FLD determination and as selective as conventional commercially available immunoaffinity columns. In the clean up of different cereals mean recoveries of 82±5%, 90±6% and 91±3%, were obtained for wheat, barley and rye, respectively, with sol-gel columns containing 1mg of anti-OTA antibodies. The detection limit (signal-to-noise ratio, 3) was 0.5 μg/kg and the limit of quantification (signal-to-noise ratio, 10) determined to be 1 μg/kg. Sol-gel columns can be reused 7 times without significant loss of recovery. After 10 applications the recovery decreased to approx. 50%.     

Synthesis of 1-aminoimidazo[5,1-a]isoquinolinium salts based on multicomponent reactions of isocyanides

A novel pseudo-four-component condensation yielding 1-aminoimidazo[5,1- a]isoquinolinium salts from isocyanides, isoquinoline, and sulfonic or bromic acids is described. The method offers several advantages including high yields of products and an easy experimental workup procedure.     

Determination of ochratoxin A in grains by immuno-ultrafiltration and HPLC-fluorescence detection after postcolumn derivatisation in an electrochemical cell

The paper presents a new sample clean-up method based on immuno-ultrafiltration for the analysis of ochratoxin A in cereals. In contrast to immunoaffinity chromatography, in immuno-ultrafiltration, the antibodies are used in non-immobilised form. Ochratoxin A was extracted with ACN/water (60/40, v/v), and the extract was loaded onto the ultrafiltration device. After a washing step with phosphate-buffered saline, containing 0.05% Tween 20, ochratoxin A was eluted with MeOH/acetic acid (99/1, v/v). The detection of ochratoxin A was carried out with high-performance liquid chromatography and a fluorescence detector coupled to an electrochemical cell (Coring cell). The electrochemical cell was used to eliminate matrix interferences by oxidising matrix compounds. The method was validated by repeatedly analysing spiked barley and rye samples as well as a certified wheat reference material. Recoveries and standard deviations (1 SD) were found to be 71 ± 9%, 77 ± 12% and 77 ± 8% in wheat, barley and rye, respectively. The limit of detection (S/N = 3) and limit of quantitation (S/N = 10) were determined to be 0.4 μg kg^-1 and 1 μg kg^-1. The analysis of the certified reference material resulted in ochratoxin A concentrations which were in the range assigned by the producer. Additionally, the effect of the electrochemical cell on other widely used clean-up techniques, namely the immunoaffinity clean-up and multifunctional columns (Mycosep #229), was evaluated. In all clean-up methods, an improvement of the chromatogram quality was registered.     

Rapid Synthesis of 3‐Aminoimidazo[1,2‐a]Pyridines and Pyrazines

p‐Toluenesulfonic acid catalyzed the one‐pot, three‐component synthesis of 3‐aminoimidazo[1,2‐a]pyridines and pyrazines through a condensation reaction of a 2‐aminoazine, an aldehyde, and an isocyanide at room temperature. This methodology affords a number of 3‐aminoimidazo[1,2‐a]pyridines in reasonable yields and short reaction times without any significant optimization of the reaction conditions.     

Caro's Acid–Silica Gel: An Efficient and Versatile Catalyst for the One-Pot Synthesis of Tetrahydrobenzo[b]pyran Derivatives

An efficient one-pot synthesis of tetrahydrobenzo[b]pyran is described. This involved the three-component reaction of aromatic aldehydes, molononitrile, and dimedone in the presence of a catalytic amount of Caro's acid supported on silica gel in ethanol/water under reflux.     

POLY [N-(4-PYRIDINIUM DICHROMATE)-P-STYRENE SULPHONAMIDE] AS AN EFFICIENT REAGENT FOR OXIDATION OF ALCOHOLS

POLY [N-(4-PYRIDINIUM DICHROMATE)-P-STYRENE SULPHONAMIDE] is readily prepared. It is a stable, mild, and efficient oxidizing reagent that can be used for oxidation of different alcohols to their corresponding carbonyl compounds in approtic solvents. This polymer can be synthesized from the reaction between poly [N-(4-pyridyl)-p-styrene sulphonamide] and CrO ₃ in a minimum amount of water. The latter polymer was prepared by free radical polymerization of [N-(4-pyridyl)-p-styrene sulphonamide] by using azobis(isobutyronitrile) (AIBN) as an initiator. N-(4-pyridyl)-p-styrene sulphonamide was synthesized from commercial 4-vinyl benzene sulphonic acid sodium salt and 4-amino pyridine. POLY [N-(4-PYRIDINIUM DICHROMATE)-P-STYRENE SULPHONAMIDE] can oxidize both aliphatic and aromatic alcohols in good yields at a temperature of 38°C and in CH ₂ Cl ₂ as solvent. One advantage in using this reagent is the mild condition of the reaction system. The synthesized compounds including polymeric reagent and carbonyl compounds were identified by HNMR and IR spectroscopy.