Impact of double cryogelation process on a macroporous dye-affinity hydrogel

Cryogels with interconnected channels allow high flow-through properties and mass transfer when dealing with complex mixtures such as non-clarified crude extracts. However, their mechanical strength can be challenged due to a large void volume inside the polymeric network. We have addressed this problem by forming a double-layer cryogel applied as a dye-affinity chromatography gel. In this study, poly(acrylamide-co-allyl glycidyl ether) cryogel was prepared at sub-zero temperature. The second layer was then prepared inside the primary cryogel under the same conditions to form a double-layer network. Cibacron Blue F3GA, a dye molecule, was immobilized on the surface of the cryogels. Bovine serum albumin was used as a model molecule to study the adsorption/elution procedure in batch and continuous modes. The maximum batch binding capacity and the dynamic binding capacity for the single-layer cryogel were 18 and 0.11, and for the double-layer cryogel were 7.5 and 0.9 mg/g of gel, respectively. However, the mechanical stability of the double-layer cryogel increased 7-fold (144 kPa). It was found that the kinetic and adsorption isotherms follow pseudo-second-order and Freundlich models, respectively. The regeneration of the columns after adsorption/elution cycles was evaluated, and no significant loss of capacity was observed after 10 cycles.     

Electrochemical synthesis and characterization of a new conducting polymer: Polyrhodanine

An antimicrobial drug, rhodanine (Rh), was electrochemically polymerized on a Pt electrode using cyclic voltammetry (CV). The high quality and homogeneous polyrhodanine (pRh) films with a dark-purple color were obtained. The chemical structure characterization was investigated by Fourier transform infrared spectroscopy (FTIR) and UV-vis spectroscopy techniques. Further, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques used to investigate thermal properties of the film. It is found that thermal stability of pRh films is relatively high. It is also observed that tetrahydrofurane (THF) and N-methyl-2-pyrrolidone (NMP) are good solvents for the polymer.     

Synthesis and photocatalytic activity of V-doped mesoporous TiO2 photosensitized with porphyrin supported by SBA-15

Research on Chemical Intermediates - A highly efficient photocatalyst was produced by immobilizing V-doped mesoporous TiO2/tetrakis(4-carboxyphenyl)porphyrin (V-TiO2/TCPP) onto SBA-15 walls, and...     

SnTCPP-modified ZnO nanorods prepared via a simple co-precipitation method: application as a new photocatalyst for photodegradation and photoreduction processes

Research on Chemical Intermediates - In this paper, ZnO nanorods were synthesized after optimizing the parameters of pH and the concentration of raw materials, reflux temperature, reflux time and...     

Novel aqueous spongy foams made of three-dimensionally dispersed wood-fiber: entrapment and stabilization with NFC/MFC within capillary foams

This article describes the preparation of novel aqueous spongy foams that are composed of three-dimensionally distributed wood-fiber networks stabilized with nanofibrillate cellulose (NFC) and/or microfibrillated cellulose (MFC). The free standing aqueous spongy foams were prepared with the entrapment of NFC and/or MFC—stabilized air-in-water (A/W) capillary foams using “gel trapping technique”. The stability of spongy foams could be controlled by manipulating the volume fraction of NFC and/or MFC and a secondary liquid immiscible with the continuous phase of the NFC and/or MFC suspension. Possible morphology and mechanical distribution of NFC and/or MFC within spongy foams were verified with optical microscope, SEM, and functional load-bearing method. Owing to three-dimensionally dispersed wood-fiber structure, ultra-lightweight (0.01–0.06 g/cm³), high porosity (>90%), and microporous (10–80 μm), the NFC and/or MFC reinforced spongy foams, improved compressional strength-vertical direction obviously, from 0.0 to more than 13.78 kPa.     

Colloidal Nanogold-Based Immunochromatographic Strip Test for the Detection of Digoxin Toxicity

Digoxin is widely used as a cardiac glycoside drug in the treatment of various heart conditions. Because it is a toxic drug, it should be regularly monitored in the serum of patients under treatment. In this study, colloidal nanogold is synthesized and the preparation of nanogold-labeled monoclonal antibody probe to digoxin is described under optimal conditions. In addition, an immunochromatographic (IC) method for digoxin analysis employing nanogold-labeled probe is developed. With this technique, it requires only 5 min to complete the quantitative detection of digoxin. The detection time is decreased 20–30 times in comparison to radioimmunoassay (RIA). The sensitivity to digoxin was about 2 ng/ml by naked eye, which is within the therapeutic and toxic ranges of digoxin. The results of serum samples obtained by IC strip were in agreement with those obtained by RIA. The IC strip was sufficiently sensitive and accurate to be used for the rapid detection of digoxin in serum samples.     

Thermodynamics of Dissociation of <Emphasis Type=Italic>ortho</Emphasis>-Hydroxyphenylhydrazo-<Emphasis Type=Italic>β</Emphasis>-diketones and of Their Complexation with Copper(II) in Aqueous–Ethanol Solutions

The thermodynamics of dissociation of 3-(2-hydroxyphenylhydrazo)pentane-2,4-dione (H ₂ L ¹ ), 5,5-dimethyl-2-(2-hydroxyphenylhydrazo)cyclohexane-1,3-dione (H ₂ L ² ), 5,5-dimethyl-2-(2-hydroxy-4-nitrophenylhydrazo)cyclohexane-1,3-dione (H ₂ L ³ ), 1-ethoxy-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H ₂ L ⁴ ) and 1-ethoxy-2-(2-hydroxy-4-nitrophenylhydrazo)butane-1,3-dione (H ₂ L ⁵ ) and of their complexation with copper(II) was studied in aqueous–ethanol solutions by potentiometry and UV–vis spectrophotometry. It was found that the thermodynamic parameters of the proton dissociation in H₂L^1–5 and of their complexation with copper(II) depend on the substituents in the aromatic and β-diketone fragments of the molecules. Thus, the acidic properties of H₂L increase from H₂L¹ to H₂L⁵, reflecting the electron-acceptor character of the substituents, whereas all of the thermodynamic functions tend to decrease with increasing electron-withdrawing capacity of the substituents. The complexation of Cu(II) with H₂L^1–5 is exothermic, which is connected with the formation of two stable chelating cycles.     

Silver Nanoparticles–Polyaniline Nanocomposite for Microextraction in Packed Syringe

A rapid, convenient and reliable method for microextraction in packed syringe (MEPS) of the loop diuretic furosemide (FUR) in urine along with high-performance liquid chromatography (HPLC) was developed. A nanocomposite based on silver nanoparticles/polyaniline (Ag-NPs/PANI) was synthesized and used as the MEPS packing material. This nanocomposite was prepared conveniently using interfacial polymerization without the need for any templates or functional dopants. The feasibility of the synthesized nanocomposites was examined by isolation of FUR from diluted urine samples. After extraction, the analyte was desorbed by 200 μL of methanol. It was then dried and the residue was dissolved in 30 μL of methanol and an aliquot of 25 μL was, finally, injected into the HPLC system. Important parameters influencing the extraction and desorption processes were optimized and 25 cycles of draw–eject gave maximum peak area, when desorption was performed. The linearity was studied by preconcentration of 5 mL of diluted urine sample spiked with a standard solution of FUR in the concentration range of 15–750 μg L^?1. The coefficient of determination was satisfactory (r ² > 0.99) and the relative standard deviation (RSD %) value under the optimized condition was 8.8 %. The limit of detection and limit of quantification were 7 and 15 μg L^?1, respectively.     

Boronate-Containing Copolymer Grafted on Eupergit C as Matrix for Affinity Chromatography: Isotherms and Kinetics Study

A stability-indicating HPLC method has been developed and subsequently validated for the simultaneous determination of domperidone and pantoprazole in commercial tablets. The proposed HPLC method utilizes Phenomenex^® Gemini C₁₈ column (150 mm × 4.6 mm i.d., 5 μm) and mobile phase consisting of methanol-acetonitrile-20 mM dipotassium hydrogen phosphate and phosphoric acid buffer pH 7.0 (20:33:47, v/v/v) at a flow rate of 1.19 mL min^?1. Quantitation was achieved with UV detection at 285 nm based on peak area with linear calibration curves at concentration ranges 0.5–5.0 μg mL^?1 for domperidone and 1.0–10 μg mL^?1 for pantoprazole (R ² > 0.999 for both drugs). The method was validated in terms of accuracy, precision, linearity, limits of detection, limits of quantitation and robustness. This method has been successively applied to pharmaceutical formulation and no interference from the tablet excipients was found. Domperidone, pantoprazole and their combination drug product were exposed to acid, base and neutral hydrolysis, oxidation, dry heat and photolytic stress conditions and the stressed samples were analyzed by the proposed method. As the proposed method could effectively separate the drug from its degradation products, it can be employed as stability-indicating method for the determination of instability of these drugs in bulk and commercial products.     

A Biomimetic Potentiometric Sensor Using Molecularly Imprinted Polymer for the Cetirizine Assay in Tablets and Biological Fluids

Despite the increasing number of applications of molecularly imprinted polymers (MIPs) in analytical chemistry, the construction of a biomimetic potentiometric sensor remains still challenging. In this work, a biomimetic potentiometric sensor, based on a non‐covalent imprinted polymer was fabricated for the recognition and determination of cetirizine. The MIP was synthesized by precipitation polymerization, using cetirizine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross linking agent. The sensor showed high selectivity and a sensitive response to the template in aqueous system. The MIP‐modified electrode exhibited Nernstian response (28.0±0.9 mV/decade) in a wide concentration range of 1.0×10^?6 to 1.0×10^?2 M with a lower detection limit of 7.0×10^?7 M. The electrode has response time of ca. 20 s, high performance, high sensitivity, and good long term stability (more than 5 months). The method was satisfactory and used to the cetirizine assay in tablets and biological fluids.