Saikh Mohammad Wabaidur

Optical ascorbic acid sensor based on the fluorescence quenching of silver nanoparticles.

A sensitive and selective fluorimetric sensor for the assay of ascorbic acid (AA) using silver nanoparticles as emission reagent was investigated. In this study, silver nanoparticles were prepared based on aqueous-gaseous phase reaction of silver nitrate solution and ammonia gas. The nanoparticles were water-soluble, stable and had a narrow emission band. They were used as a fluorescence probe for the assay of ascorbic acid on its quenching effect on the emission of silver nanoparticles. The principal reason for quenching is likely to be a complexation between ascorbic acid and silver nanoparticles. The quenching mechanism was established by Stern-Volmer law. Under the optimum conditions, the quenched fluorescence intensity was linear with the concentration of ascorbic acid in the range of 4.1 x 10(-6) to 1.0 x 10(-4) m (r = 0.9985) with a detection limit of 1.0 x 10(-7) m. The RSD for repeatability of the sensor for the assay of ascorbic acid concentration of 3.0 x 10(-5) and 4.0 x 10(-6) m was found to be 1.5 and 1.3%, respectively. The proposed method was applied to the determination of ascorbic acid in vegetables and vitamin C tablets.

High-Performance Liquid Chromatography Analysis of Phenolic Acid, Flavonoid, and Phenol Contents in Various Natural Yemeni Honeys Using Multi-walled Carbon Nanotubes as a Solid-Phase Extraction Adsorbent

A simple method has been described for simultaneous determination of phenolic acid, flavonoid, and other phenol contents in various natural honey samples collected from various regions of Yemen. Multi-walled carbon nanotubes were used as a solid-phase adsorbent for extraction of the polyphenols from honey samples. The total contents of phenolic acids, flavonoids, and phenolic components of the 12 different samples were found in the range of 363-2658, 261-1646, and 224-1355 μg/100 g of honey samples, respectively. The major phenolic acid, flavonoid, and phenolic compound in these samples were found to be 4-hydroxybenzoic acid (1410 μg/100 g), chrysin (850 μg/100 g), and cinnamic acid (1336 μg/100 g), respectively. A total of 25 compounds (10 phenolic acids, 9 flavonoids, and 6 phenols) were analyzed, and a total of 24 were detected, while only 23 compounds were determined quantitatively in the honey samples. The developed method showed potential usefulness for the analysis of honey and was used for the determination of polyphenols in honey extracts.

Development of a sensitive flow‐injection–chemiluminescence detection method for the determination of laevodopa

A simple chemiluminometric method using flow injection has been developed for the determination of levodopa, based on its sensitizing effect on the weak chemiluminescence (CL) reaction between Na(2)SO(3) and acidic KMnO4. Under optimum experimental conditions, the CL intensity was linearly related to the concentration of levodopa from 3.4 x 10(-8) to 2.4 x 10(-5) mol/L and the detection limit was 1.1 x 10(-8) mol/L (s:n = 3). The relative standard deviation (RSD) of the proposed method calculated from 20 replicate injection of 3 x 10(-7) mol/L levodopa was 3.3%. The correlation coefficient was 0.997. The method was successfully applied to the determination of levodopa in commercial pharmaceutical formulations and spiked urine samples.

Structural elucidation and physicochemical properties of mononuclear Uranyl(VI) complexes incorporating dianionic units.

Two derivatives of organouranyl mononuclear complexes [UO2(L)THF] (1) and [UO2(L)Alc] (2), where L = (2,2′-(1E,1′E)-(2,2-dimethylpropane-1,3-dyl)bis(azanylylidene, THF = Tetrahydrofuran, Alc = Alcohol), have been prepared. These complexes have been determined by elemental analyses, single crystal X-ray crystallography and various spectroscopic studies. Moreover, the structure of these complexes have also been studied by DFT and time dependent DFT measurements showing that both the complexes have distorted pentagonal bipyramidal environment around uranyl ion. TD-DFT results indicate that the complex 1 displays an intense band at 458.7 nm which is mainly associated to the uranyl centered LMCT, where complex 2 shows a band at 461.8 nm that have significant LMCT character. The bonding has been further analyzed by EDA and NBO. The photocatalytic activity of complexes 1 and 2 for the degradation of rhodamine-B (RhB) and methylene blue (MB) under the irradiation of 500W Xe lamp has been explored, and found more efficient in presence of complex 1 than complex 2 for both dyes. In addition, dye adsorption and photoluminescence properties have also been discussed for both complexes.

Synthesis, Structural Characterization and Antimicrobial Activity of Cu(II) and Fe(III) Complexes Incorporating Azo-Azomethine Ligand

We are reporting a novel azo-azomethine ligand, HL and its complexes with Cu(II) and Fe(III) ions. The ligand and its complexes are characterized by various physico-chemical techniques using C,H,N analyses, FT-IR, 1H-NMR, ESI-MS and UV-Vis studies. TGA analyses reveal complexes are sufficiently stable and undergo two-step degradation processes. The redox behavior of the complexes was evaluated by cyclic voltammetry. Furthermore, the ligand and its complexes were tested for antimicrobial activity against bacterial and fungal strains by determining inhibition zone, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The complexes showed moderate antimicrobial activity when tested against Gram +ve and Gram −ve bacterial strains. To obtain insights into the structure of ligand, DFT studies are recorded. The results obtained are quite close to the experimental results. In addition, the energy gap, chemical hardness, softness, electronegativity, electrophilic index and chemical potential were calculated using HOMO, LUMO energy value of ligand.

CL sensitisation of tris-(bipyridyl) ruthenium (II) – cerium (IV) reaction system by AgNPs for determination of GFX

The flow injection combined with tris-(bipyridyl) ruthenium (II)-cerium (IV) chemiluminescence (CL) method based on the sensitisation of silver nanoparticles (AgNPs) has been established for the quantitative analysis of gatifloxacin (GFX). AgNPs were synthesised using the reaction between ammonia gas and silver nitrate solution and was used to increase the CL intensity of the proposed system. The enhancement of CL intensity was linear with the concentration of GFX added. Effects of different experimental parameters were studied. Under the optimal conditions, the linear relationship was established between the concentration range of 1.4 × 10-10-4.5 × 10-8 M, with the correlation coefficient (r2) 02E9999. The limit of detection was found to be 4.6 × 10-11 M. The relative standard deviation obtained was 3.2% for six replicate measurements of GFX (1.2 × 10-9 M). The proposed CL method was applied to the commercial drug and the result was in agreement with the labelled amount. The technique was further adopted to the analysis of GFX in spiked urine samples. Negligible interference was found (variation in CL intensity <5%) from a few common foreign excipients applied in preparation of pharmaceutical drug. The comparative results with a few reported methods indicates that the proposed method is more sensitive than other methods..

UPLC-MS method for the simultaneous determination of polyphenols in honey using MWCNTs as extraction sorbents

The intention of present research is to enhance the dissolution rate of water insoluble drugs like Glyburide. It is a poorly soluble drug and the rate of its oral absorption is often controlled by the dissolution rate in the gastrointestinal tract. There are several techniques to enhance the dissolution of poorly soluble drugs, in which the liquisolid compacts is a promising technique. Different formulations were prepared by using different vehicles and carriers and aerosil is used as the coating material. The empirical method as introduced by Spireas and Bolton was applied to calculate the amounts of coating and carrier materials required to prepare glyburide liquisolid tablets. Based upon this method, improved flow characteristics and hardness of the formulation has been achieved by changing the proportion of carrier and coating material ratio. In vitro dissolution profiles of the liquisolid formulations were studied and compared with conventional formulation in 0.1N HCl. It was found that liquisolid tablets formulated with PEG 400 and Avicel pH102 produced high dissolution profile and they showed significant higher drug release rates than conventional tablets due to increase in wetting properties and surface of drug available for dissolution. Drug-excipient interaction studies showed that there is no interaction between the drug and excipients. In conclusion, development of glyburide liquisolid tablets is a good approach to enhance the dissolution rate which increases bioavailability.A is naturally abundant in the crust of the earth and introduced into the aquatic system through dissolution and weathering of minerals. Chronic ingestion of arsenic in water may cause various diseases, including cancer and keratosis. A guideline for arsenic in drinking water has been set at 10 ppb of total arsenic by the World Health Organization (WHO). However, inorganic forms of arsenic, such as arsenites [As (III)] and arsenates [As (V)], are much more toxic than the organic forms as the monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Hence the quantitation of specific arsenic species may be more meaningful than the total arsenic determination for the evaluation of the health risks from arsenic-contaminated drinking water. We report a highly sensitive way of arsenic speciation using a commercial Capillary Electrophoresis (CE) instrument equipped with a UV absorbance detector. We used a counter-flow electrokinetic supercharging technique to enhance the detection sensitivity. Electrokinetic supercharging is one of the most powerful sample stacking methods that combine field amplified sample injection and transient isotachophoresis. In counter flow electrokinetic supercharging, a constant counter pressure is applied during sample injection in order to counterbalance the movement of the injected sample zone, obtaining a pronounced increase in the amount of sample injected and the portion of the capillary available for electrophoresis.T aim of the present study was to investigate the differences in chemical composition of essential oils extracted from leaves and fruits of the Algerian Eucalyptus globulus (E. globulus) plant, using a semi quantitative gas-chromatography coupled with mass spectrometry (GC/MS) method. The oil extraction yields were about 2.53±0.1% for the leaves and 3.11±0.4% for the fruits. The GC/ MS analysis allowed identifying 30 volatile compounds for essential oil from leaves (LO) and 34 for the essential oil from fruits (FO). Monoterpenes and oxygenated monoterpenes are present at a high percentage in leaves essential oil (86%) while sesquiterpenes and oxygenated sesquiterpenes compounds are the major compounds present in the fruit essential oil (74%). The results revealed that in the fruit essential oil, aromadendrene is the major sesquiterpenes compound (1027 mg/L), followed by globulol (1147 mg/L) and ledene (152 mg/L). As a comparison, in the leaves, 1, 8-cineol (1568 mg/L) is the major compound followed by isovaleraldehyde (285 mg/L) and α-carveol (155 mg/L).T existence, reactions, structures and properties of compounds occurring in nature, and their synthetic analogues are explainable by the idea of two-center two-electron bond. These families contain either electron exact or electron rich building blocks from the viewpoint of electron structure. Electron deficient building blocks have never been found in nature, and exist only in synthetic species. Boron cluster compounds (BCCs) create the most intensely investigated family of species with electron deficient cluster. Their existence has been explained by the accumulation of unique electron deficient bonds, which bind together three boron atoms or, sometimes, their substitutes, in clusters. Pronouncedly electron deficient clusters either determine or substantially affect properties of BCCs, and their prospects. Therapeutical prospects attract the highest attention now, and many compounds with boron clusters are synthesized as candidates for therapeutical uses. These compounds must pass through mandatory studies and checks, which require variety of chemical analyses, identically with other compounds. However, analytical methods do not exist for analyses of compounds with boron clusters. The pieces of knowledge from chiral separation of BCCs prove the dissimilarity of some analytical properties of species with and without boron clusters, and indicate the absence of criteria for the a priori estimation of different analytical properties for compounds with and without clusters. Thus, missing analytical methods cannot be derived from existing knowledge. Analytical research of BCCs motivated by their medical prospects is the best way to preventive elimination some obstacles, which may hamper medical uses of compounds with boron clusters.

UPLC−MS Method for the simultaneous determination of pharmaceutical drugs in waste water samples

In this study, graphene was functionalized via acid oxidation in the presence of a mixture of concentrated sulfuric acid (H2SO4) and nitric acid (HNO 3 ). Thus oxidized graphene (o-graphene) were silanized using a coupling agent, 3-aminopropyltriethoxsilane (3-APTES) resulting in functionalized graphene (f-graphene). Chitosan/graphenenanocomposites films have been prepared by the mixing aqueous solution of chitosan and multi-performance graphene in the present of diluted acetic acid. The chemical structure, thermal stability and mechanical properties of the nanocomposite films have been investigated by the wide-angle X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Atomic Force Microscopy (AFM), and mechanical test via Universal Testing Machine (Instron 8841). The results revealed that chitosan and graphene could mix with each other homogeneously and the mechanical properties of the as-prepared films were improved significantly over that of the pure chitosan film. These composites films have potential applications as biomaterials or packing materials.I experiments were conducted to observe the effects of organic amendments, which were produced from sewage sludge and food waste through pyrolysis, composting and drying processes, on immobilization of cadmium (Cd) in contaminated soil. The results show that concentrations of acid extractable Cd were significantly decreased (5.9-7.6 percentages) with application of 50 g.kg-1 pyrolytic products and composting products during 60 d incubation period, while were increased (0.9-3.0 percentages) with drying products application under the same condition. Concentrations of Fe-Mn oxides bound Cd were decreased and concentrations of organic bound and residual Cd were increased by different levels with application of all amendments. The performances of Cd immobilization with various sludge derived products as amendment presented in following order: Pyrolytic product>composting product>drying product. The performances of Cd immobilization with various food waste derived products as amendment presented in following order: Composting product>pyrolytic product>drying product. Soil pH, cation exchange capacity (CEC) and organic matter were also changed by different levels with application of all amendments. According to the result of correlation analysis, there was significant correlation between soil pH and Cd fractions. Therefore, it could be speculated that soil pH change is one of the main factors in charge of Cd forms distributions in soil with application of organic amendments from sludge and food waste. Based on experiment results, it can be concluded that different processing techniques result in distinguishing properties of organic amendment from same matrix and thus impact its performance of Cd immobilization in soil. As far as environmental effects and risks to be concerned, biochar produced from sewage sludge and food waste through pyrolysis processing could be a promising organic amendment for Cd contaminated soil remediation.C (Cr) is one of the most and important trace metals which can be present in two oxidation states: Toxic Cr(VI) and non-toxic (Cr III). Cr(III) is an important microelement for plant and animal nutrition and essentials for the maintenance of glucose as well as for the lipid and protein metabolism. With regard to human health, Cr(III) is a required nutrient, with 50-200 μg per day recommended for adults. On the contrary, Cr(VI) is toxic and carcinogenic, leading to lung cancer, skin allergy and probably also to asthma and renal diseases. A toxic effect for the biological systems is attributed to the ability of Cr(VI) to migrate across the cell membrane, thus enhancing the intracellular chromium concentration. Hexavalent chromium is rarely found in nature and is generally man-made, especially in fumes generated during the ferrochrome production. The permissible exposure limit (PEL) of chromium in air is 5 μg m-3 measured as Cr(VI). The dust with Cr(VI) could be a source of contamination of medicinal plants. Therefore, it is essential to monitor the concentration of Cr(VI) in the environment, to determine the risk of Cr(VI) to human health, not only from air breathing, but from the dust which settles on agricultural products grown in vicinity of chromium smelters and when into medicinal plants. For these studies, the samples of industrial dust, soil, bark of trees and medicinal plants samples were collected in the vicinity of chromium smelters and from local market. All measurements were carried out using a Perkin Elmer atomic absorption spectrometer model AAnalyst 600 with Zeeman background correction.Aminomethylation of benzotriazole was carried out by treating benzotrialzole with formaldehyde and 4-aminosalicylic acid. The resultant compound was designed as 1-(4-carboxy-3-hydroxy-4-phenyl amino methyl) benzotriazole. The transition metal complex of Cu2+, Co , Ni, Mnand Zn of 1-(4-carboxy-3-hydroxy-4-phenyl amino methyl) benzotriazole have been prepared. Elemental analysis, spectral studies, magnetic moment determination, molar conductivity measurement and microbial activity of 1-(4-carboxy-3-hydroxy4-phenyl amino methyl) benzotriazole and its metal complexes were carried out.N chiral N-phosphoramide and N-phosphonyl imines were found to be efficient asymmetric chiral auxiliaries. Various nucleophilic addition reactions such as aza-Henry reaction, aza-Darzens reaction, Strecker reaction were performed on these chiral amines and desired products were obtained in excellent chemical yields (94-99%) and diastereo selectivities (upto >99%). These reactions were confirmed to follow the GAP chemistry (group assisted purification chemistry) process, which can avoid traditional chromatography and re-crystallization purifications, i.e., the chiral product bearing a chiral N-‐ phosphonyl group can simply be purified by washing the solid crude products with hexane or hexane:ethylacetate mixture, hence provide a green process to purify organic compounds and motivates the synthetic community to search more of such reagents/processes. Moreover, the chiral auxiliary can be cleaved under acidic conditions and can be easily recovered without loss of chirality.T human population is suffering increased exposure to existing and new chemicals and environmental toxins. Among the various environmental toxins, PAHs are an important class of environmental contaminants, and many PAHs are known or suspected carcinogens. PAHs are produced in the environment through the incomplete burning of organic fuels and cover wide classes of compounds. Exposure to some of these compounds is well-known to cause cancer in mice and they are suspected to be carcinogenic compounds for humans. The photocatalytic degradation of anthracene in aqueous solutions in the presence of TiO2 suspension has been investigated with the use of UV-irradiation. This study includes comparison between two types of titanium dioxide (P25 and UV100), also includes effect of different parameters on photocatalytic oxidation of anthracene by titanium dioxide were studied, such as: anthracene concentration, pH of aqueous solution, light intensity, addition of H2O2 and temperature on photocatalytic oxidation. The results showed that titanium dioxide, P25 type is better than UV100 type. The results also showed the optimum conditions for degradation process by photocatalytic oxidation are; perfect concentration of anthracene is 25 ppm, 6.8 of pH is the best value for anthracne, 2.5 mW. Cm-2 of light intensity, degradation rate of anthracene without addition of hydrogen peroxide is fastest and 308.15K is the appropriate degree of temperature. The results indicated that the photocatalytic degradation of anthracene was well described by pseudo first order kinetics according to the LangmuirHinshelwood model. The effect of temperature on the efficiency of photodegradation of anthracene was also studied in the range 278.15-308.15 K. The activation energy was calculated according to Arrhenius plot, and was found equal to 12.76 kJ.mol-1 for TiO2 (Degussa P25). The main product of anthracene after degradation was 9, 10-anthraquinone which was identified by GC-MS.The intermediate compound that produced of degradation of anthracene was 9,10-anthraquinone. This product characterises by FTIR and GC-MS, the complete degradation for 9-10 anthraquinone was achieved.The activity of lipase‐catalysedhydrolysis of olive oil in SDS‐1‐butanol‐olive oil‐watermicroemulsionswas investigated. The kinetics of lipases in reverse microemulsions and water were also compared. The influences of the characteristic parameters of these systems, such as pH, temperature (T), molar ratio (vo) of water to SDS, the concentrations of enzyme and substrate, on the activity of an enzyme were examined. According to the optimum conditions the production and activity were measured at pH1⁄44, T1⁄440 8C, vo1⁄412. The activation energy of the reaction was calculated from the Arrhenius plot. It was found that the hydrolysis reaction obeyedMichaelis–Menten kinetics and the apparentMichaelis Km,a and the apparentmaximal reaction rate Vmax were determined. The effect of microemulsions surfactant (SDS) on enzymatic activity was also discussed.

Estimation of isatin in spiked plasma samples using high performance liquid chromatography

An isocratic analytical method based on liquid chromatographic determination with UV detection is described for the determination of isatin in spiked plasma and in its synthetic mixture. The separation of the isatin was achieved on betasil C-8 column using mobile phase consisting of a binary mixture of acetonitrile and buffer (Na2CO3 + NaHCO3). Linearity, accuracy and precision were found to be acceptable over the concentration range (5 - 150 mg/L). LOD and LOQ were found to be 1.09 mg/L and 3.3 mg/L, respectively. The developed LC method with UV-visible detection offers simplicity, selectivity, precision and accuracy. It produces a symmetric peak shape and reasonable retention time. No interference has been observed with the excipients found in the drug formulation. Forced degradation studies were also conducted on the isatin samples and the results shows that the newly developed method is able to determine the content of isatin in presence of its degradation products. The proposed method when applied to the determination of isatin in spiked plasma samples produced a recovery ranging from 96.0%-98.2%.