Akheel Ahmed Syed

REVIEW : POLYANILINE : A NOVEL POLYMERIC MATERIAL

Polyaniline synthesis by chemical and electrochemical methods is reviewed. The considerable progress which has been made in characterizing and understanding the properties of polyaniline derived from aniline is discussed. Finally, the progress towards technological applications is evaluated.

Novel reactions for simple and sensitive spectrophotometric determination of nitrite.

Nine spectrophotometric methods based on new reactions for the determination of tracer amounts of nitrite in environmental samples were developed. Replacement of toxic reagents was explored to attain the standards of clean chemistry. These methods utilize two classes of compounds namely; phenoxazines and sulphonamides, the well established drugs in the presence of limited amounts of hydrochloric acid. The methods were based on the oxidation of sulfanilamide (SAA), sulfadoxine (SDX) or sulfamethoxazole (SMX) by nitrite in hydrochloric acid medium and coupling with phenoxazine (PNZ), 2-chlorophenoxazine (CPN) or 2-trifluoromethylphenoxazine (TPN) which yielded red colored derivatives having an absorbance maximum in the range 530-540nm and were stable for about 4h. Beers law was obeyed for nitrite in the concentration range 0.13-1.60mugmL(-1). The reaction conditions and other important analytical parameters were optimized to enhance the sensitivity of the methods. Interference if any, by non-target ions was also investigated. The methods were applied determining nitrite in environmental samples. The performance of these methods were evaluated in terms of Students t-test and variance ratio F-test to find out the significance of proposed methods over the reference spectrophotometric method.

Polyaniline: Reaction stoichiometry and use as an ion-exchange polymer and acid/base indicator

Abstract An iodometric method has been used to establish that in the synthesis of polyaniline by the oxidative polymerization of aniline with ammonium peroxudisulfate, ∼2.5 electrons are involved per (C 6 H 4 )N repeat unit. It is also demonstrated that polyaniline can act as an ion-exchange polymer and as an acid/base indicator.

LC determination of finasteride and its application to storage stability studies

The development of a simple, sensitive, rapid, and reproducible reversed-phase high-performance liquid chromatographic assay of finasteride (proscar) in preformulation, and its application to forced degradation studies has been carried out. The method showed excellent linearity (r2 > or = 0.9997) in the range 20-600 microg x ml(-1) using a Shimpak C8 column (5 microm, 15.0 cm x 4.6 mm) and UV-detection (210 nm) at ambient temperature (25 +/-1 degree C) with a mobile phase of acetonitrile and water (95:05,v/v) and flow rate of 0.7 ml x min(-1). All peaks are eluted in < 10 min and the method has good precision. This method showed good efficiency for the analysis of forced degraded samples, studied at different temperatures and humidities. The results manifest that the shelf-life of proscar is greater than two years at room temperature, under proper storage conditions.

Thermal Degradation Kinetics of Polyurethane/Organically Modified Montmorillonite Clay Nanocomposites by TGA

Polyurethane (PU) has been prepared by using polyether polyol (jagropol oil) and 1,6- hexamethylene diisocyanate (HMDI) as a cross-linker. The organically modified montmorillonite clay (MMT) is well-dispersed into urethane matrix by an in situ polymerization method. A series of PU/MMT nanocomposites have been prepared by incorporating varying amounts of nanoclay viz., 1, 3, 5 and 6 wt %. Thermogravimetric analysis (TGA) of the PU/MMT nanocomposites has been performed in order to establish the thermal stability and their mode of thermal degradation. The TGA thermograms exhibited the fact that nanocomposites have a higher decomposition temperature in comparison with the pristine PU. It was found that the thermal degradation of all PU nanocomposites takes place in three steps. All the nanocomposites were stable up to 205°C. Degradation kinetic parameters of the composites have been calculated for each step of the thermal degradation processes using three mathematical models namely, Horowitz–Metzger, Coats–Redfern and Broidos methods.

Thermal Characteristics of Nanostructured Filler-Incorporated Polyvinylester Nanocomposites

The aim of the present investigation is to probe the influence of organically modified layered silicates (o-montmorilonite, o-MMT) content on mechanical and thermal behaviors of vinyl ester/o-MMT (organoclays) nanocomposites. Polyvinyl ester nanocomposites were synthesized with o-MMT by in-situ polymerization technique. The prepared vinyl ester/o-MMT composites have been characterized for mechanical properties such as tensile properties and impact strength. Thermal characteristics of the vinyl ester/o-MMT nanocomposites were evaluated by using differential scanning calorimeter (DSC), thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMA). The thermal degradation kinetic parameters such as activation energy (Ea) of nanocomposites were evaluated by using three mathematical models, namely Horowitz–Metzger, Coats–Redfern and Broidos methods.

Poly(aniline): a conducting polymer as a novel anion-exchange resin

Poly(aniline) resins were prepared by a one-step redox polymerization of aniline with persulfate in various molar ratios. The resin samples were characterized by elemental analysis, solid-state conductivity and solid-state cross-polarization magic angle spinning 13C nuclear magnetic resonance studies. The resins were used for binary and tertiary separations.

Spectrophotometric determination of certain benzimidazole proton pump inhibitors

Spectrophotometric method for the determination of certain proton pump inhibitors belonging to the benzimidazole class of compounds has been developed. The method is based on the reaction of omeprazole, lansoprazole, pantoprazole, rabeprazole and esomeprazole with iron (III) and subsequent reaction with ferricyanide under neutral condition which yields Prussian blue product with maximum absorption at 720–730 nm. The commonly encountered excipients and additives that often accompany pharmaceutical preparations did not interfere with the determination. The method was applied for the determination of omeprazole, lansoprazole, pantoprazole, rabeprazole and esomeprazole in pharmaceutical preparations and no difference was found statistically. Thus, the spectrophotometric method can be applied as inexpensive, rapid, easy, accurate and precise method for the routine analysis of the five proton pump inhibitors in pharmaceutical preparations.

Sensitive and Selective Spectrophotometric Determination of Hg(II), Ni(II), Cu(II) and Co(II) Using Iminodibenzyl and 3-Chloroiminodibenzyl as New Reagents and Their Applications to Industrial Effluents and Soil Samples

Iminodibenzyl (IDB) and 3-chloroiminodibenzyl (Cl-IDB) are proposed as a new class of spectrophotometric reagents for the determination of micro amounts of mercury(II), nickel(II), copper(II) and cobalt(II) in the presence of 3-methyl-2-benzothiazoline hydrazone hydrochloride hydrate (MBTH) or 4-aminoantipyrine (AAP) as electrophilic coupling reagents. The reaction is carried out in neutral aqueous medium. The blue colour formed shows maximum absorbance at 660 nm using MBTH and 630 nm with AAP. The methods obey Beers law. The molar absorptivity and Sandells sensitivity show different values with different metals and reagents. The blue colour can also be extracted quantitatively which can be exploited as an efficient extractive spectrophotometric technique for the separation of metal ion from other interfering species. As many as 15 cations and 12 anions and/or complexing agents listed do not interfere. Both the methods have good reproducibility and can be satisfactorily applied in the determination of metals in industrial effluents and soil samples.

Anion-exchange studies on electrically conducting polymers: Polyanilines

Abstract Electrically conductive, anion-exchange polyaniline resins are prepared by one-step redox polymerization of aniline with ammonium persulphate, potassium dichromate, cerium(IV) sulphate, or sodium vanadate. The resulting polymers are characterized by solid-state techniques, viz. conductivity, 13 C cross- polarization magic-angle spinning (CPMAS) NMR, and thermogravimetric studies. The polymers are used for binary and tertiary separations.