Rita Dhodapkar

Molecularly imprinted microspheres and nanoparticles prepared using precipitation polymerisation method for selective extraction of gallic acid from Emblica officinalis.

This paper reports the preparation of gallic acid (GA) molecularly imprinted polymers (MIPs) by the precipitation polymerisation and highlights the effect of porogen on particle size and specific molecular recognition properties. MIP, M-100 prepared in the porogen acetonitrile and MIP, M-75 prepared in a mixture of acetonitrile-toluene (75:25 v/v), resulted in the formation of microspheres with approximately 4μm particle size and surface area of 96.73m(2)g(-1) and nanoparticles (0.8-1000nm) and a surface area of 345.9m(2)g(-1), respectively. The Langmuir-Freundlich isotherm study revealed that M-75 has comparatively higher number of binding sites which are homogenous and has higher affinity for GA. The MIPs selectively recognised GA in presence of its structural analogues. Pure GA with percent recovery of 75 (±1.6) and 83.4 (±2.2) was obtained from the aqueous extract of Emblica officinalis by M-100 and M-75, respectively and hot water at 60°C served as the eluting solvent.

Optimal selection of full scale tannery effluent treatment alternative using integrated AHP and GRA approach

The selection of optimal wastewater treatment alternative involves multiple objectives and/or criteria and hierarchy process. This study integrates analytical hierarchy process (AHP) and grey relation analysis (GRA) for optimal selection of full scale tannery effluent treatment plants. For this purpose, seven tanneries and their effluent treatment facilities are studied in detail in Southern India. The objective hierarchy criterion is considered based on three factors; economic, technical, and administrative, each ofwhich againinvolves hierarchy of indices. A realistic treatment alternative selection is obtained since all the data used is on actual basis.The biggest advantage of this approach is that it provides the information regarding the scope for further improvement in existing treatment options. The study indicates that the AHP and grey relation analysisare powerful tools that can be used for implementation of appropriate wastewater treatment technology.

Validation of computational approach to study monomer selectivity toward the template Gallic acid for rational molecularly imprinted polymer design

Gallic acid (GA) is important for pharmaceutical industries as an antioxidant. It also finds use in tanning, ink dyes and manufacturing of paper. Molecularly imprinted polymers (MIP), which are tailor made materials, can play an excellent role in separation of GA from complex matrices. Molecular recognition being the most important property of MIP, the present work proposes a methodology based on density functional theory (DFT) calculations for selection of suitable functional monomer for a rational design of MIP with a high binding capacity for GA. A virtual library of 18 functional monomers was created and screened for the template GA. The prepolymerization template-monomer complexes were optimized at B3LYP/6-31G(d) model chemistry and the changes in the Gibbs free energy (ΔG) due to complex formation were determined on the optimized structures. The monomer with the highest Gibbs free energy gain forms most stable complex with the template resulting in formation of more selective binding sites in the polymeric matrix in MIPs. This can lead to high binding capacity of MIP for GA. Amongst the 18 monomers, acrylic acid (AA) and acrylamide (AAm) gave the highest value of ΔG due to complex formation with GA. 4-vinyl pyridine (4-Vp) had intermediate value of ΔG while, methyl methacrylate (MMA) gave least value of ΔG due to complex formation with GA. Based on this study, the MIPs were synthesized and rebinding performance was evaluated using Langmuir-Freundlich model. The imprinting factor for AA and AAm based MIPs were 5.28 and 4.80 respectively, 4-Vp based MIP had imprinting factor of 2.59 while MMA based MIP exhibited an imprinting factor of 1.95. The experimental results were in good agreement with the computational predictions. The experimental data validated the DFT based computational approach.

Quantum chemical density functional theory studies on the molecular structure and vibrational spectra of Gallic acid imprinted polymers.

Gallic acid (GA) is known by its antioxidant, anticarcinogenic properties and scavenger activity against several types of harmful free radicals. Molecularly imprinted polymers (MIPs) are used in separation of a pure compound from complex matrices. A stable template-monomer complex generates the MIPs with the highest affinity and selectivity for the template. The quantum chemical computations based on density functional theory (DFT) was used on the template Gallic acid (GA), monomer acrylic acid (AA) and GA-AA complex to study the nature of interactions involved in the GA-AA complex. B3LYP/6-31+G(2d,2p) model chemistry was used to optimize their structures and frequency calculations. The effect of porogen acetonitrile (ACN) on complex formation was included by using polarizable continuum model (PCM). The results demonstrated the formation of a stable GA-AA complex through the intermolecular hydrogen bonding between carboxylic acid groups of GA and AA. The Mulliken atomic charge analysis and simulated vibrational spectra also supported the stable hydrogen bonding interaction between the carboxylic acid groups of GA and AA with minimal interference of porogen ACN. Further, simulations on GA-AA mole ratio revealed that 1:4 GA-AA was optimum for synthesis of MIP for GA.

Studies of the Molecular Recognition Abilities of Gallic Acid-Imprinted Polymer Prepared Using a Molecular Imprinting Technique

The present work compares the molecular recognition abilities of two molecularly imprinted polymers (MIPs) synthesized using two different functional monomers, viz. acrylamide (AA) and 4-vinylpyridine (4-Vp), employing gallic acid (GA) as the template using the non-covalent imprinting approach employing ethylene glycol dimethacrylate (EGDMA) as the cross-linker and 2,2-azo-bis-2-isobutyronitrile (AIBN) as an initiator in the porogen acetonitrile by thermal polymerization. The change in the electronic stabilization energies (ΔE) of the template–monomer complexes formed between the template and functional monomers in the presence of the porogen were computed using Density Functional Theory (DFT) to interpret the nature of the interactions between them and to compare their stabilities. A systematic investigation of the molecular recognition abilities of the synthesized MIPs has been carried out by applying the Langmuir–Freundlich (L–F) adsorption isotherm model. The binding parameters obtained from the L–F model demonstrate that MIPAA exhibited a higher specific molecular recognition ability towards the template molecule.

Molecular Imprinting: Mimicking Molecular Receptors for Antioxidants

Molecularly imprinted polymers (MIPs) have been demonstrated to be a promising class of biomimetic materials that can be tailored to meet specific end use recognition requirements. Molecular imprinting is achieved by the interaction, either covalent or non-covalent between complementary groups in a template molecule and functional monomer units through polymerization. MIPs have been widely employed for divers applications such as chiral separation, chemical sensing, catalysis, drug screening, chromatographic separations and solid phase extraction. During respiration and metabolism, human body produce free radicals as by products, which can damage genetic material, lipids and proteins leading to several fatal diseases such as Cancer, Cardio-vascular disease, Alzheimer’s disease, Immune dysfunction etc. Antioxidants define a family of natural or synthetic nutrients in food, which acts as free radical scavengers. They are present in complex matrix such as herbs, fruit pulp in small concentration, either combined or in free form. Although several techniques have been developed for their detection, (e.g. HPLC, Thin layer chromatography, Capillary gas chromatography, Supercritical fluid chromatography), to achieve highly specific and sensitive analysis, high affinity, stable and specific recognition agents are needed. In this review, special attention is paid to the MIPs based analytical methods for antioxidants, focusing on solid phase extraction, chromatographic and non chromatographic separations and sensing approaches as well as on novel approaches for the discovery of new imprinted materials for antioxidants.

Synthesis of C-Doped TiO2 Nanoparticles by Novel Sol-Gel Polycondensation of Resorcinol with Formaldehyde for Visible-Light Photocatalysis

Nanosized C-doped TiO 2 was prepared by a new method based on resorcinol-formaldehyde (RF) gel formation in situ during hydrolysis of Ti precursor (TTIP, titanium tetraisopropoxide). XRD, DRS, EDX, SEM and HRTEM results confirmed that the carbon in the sample existed as free carbon (C–C), carbonate carbon (–CO 3 ) and doped into lattice of TiO 2 (Ti–C), resulting in red shift of optical adsorption edge and band gap narrowing. The photo activity of the C-doped TiO 2 , tested on 2-chlorophenol, revealed that it was more active under visible light (k vis = 3.50 × 10 −3 min −1 ).

Effect of some polymerization methods on the imprinting performance of molecularly imprinted polymers for molecularly imprinted solid-phase extraction application

The present work describes a solid-phase extraction (SPE) procedure using the molecularly imprinted polymers (MIPs) in order to obtain a cleaner extract and high recovery from a highly complex and aqueous herbal matrix. MIPs with a similar composition of precursors were synthesized by bulk (MIPB), precipitation (MIPP) and reverse microemulsion polymerization (MIPR) methods, and the resulting MIPs were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The MIPs were used as sorbent in SPE procedure to study their imprinting performance in the aqueous conditions. The molecularly imprinted solid-phase extraction (MISPE) procedure for selective extraction of gallic acid (GA) from the herbal extract was performed. MIPR have shown the superior performance with the 86% extraction of GA. It was observed that the morphology of the MIPs can be enhanced using various polymerization methods for improved SPE application.

Influence of porogens on the specific recognition of molecularly imprinted poly(acrylamide-co-ethylene glycol dimethacrylate)

Molecularly imprinted polymers (MIPs) are the materials mimicking the function of biological receptors and offer many possibilities for the development of novel composite materials. A computational approach was used to study the influence of porogen on the stability of template-monomer complex for rational design of MIPs. The effect of porogenic solvent was computed through polarizable continuum model, followed by the comparison of the binding energies (ΔG) of the template-monomer complexes in different porogens. MIPs were prepared for Gallic acid by thermal polymerization method, using acrylamide as functional monomer and ethylene glycol dimethacrylate as crosslinker in the presence of three different porogens, to validate the results of computational approach. The MIPs were characterized by the FT-IR, SEM, Brunauer–Emmett–Teller surface area characterization techniques and swelling analysis to study the influence of porogen on the morphology of MIPs. The performance of prepared MIPs was evaluated by batch binding experiments, Langmuir-Freundlich isotherm model and selectivity experiments. MIP prepared in THF showed the highest binding capacity and selectivity with an imprinting factor of 7.74. The results of quantum chemical computational analysis were in good accordance with the experimental results.

Treatment of spent broth from an antibiotic manufacturing unit using anaerobic fixed film fixed bed reactor

Abstract Studies on bench scale reactor were undertaken to determine its performance at various organic loading rate (OLR) and hydraulic retention time (HRT). The results indicated BOD and COD removals in the range of 67.2–77.4% and 57.8–69.1% respectively at the OLRs between 0.84 and 2.5 kgCOD/m3 d and HRT of 10 days. Daily gas production was measured by gas flow meter. Daily gas production varied between 0.268 and 0.326 m3/kgCOD added at the different OLRs. Studies were also carried out at lower HRT of 5 days. But BOD/COD removals reduced and correspondingly gas production also reduced. Gas composition remained constant at both the HRT and the Methane content was around 65–68% while the CO2 was around 32–35%. This paper discusses in detail the feasibility of upflow anaerobic fixed film fixed bed (UAFFFB) reactor system in treating the strong spent broth from the antibiotic industry.