VOLUME 26, NO4, DEC 2004

Interaction of Poly (N-vinyl 2-pyrrolidone) with a Bisazo Dye in Aqueous Solution

The binding mechanism of 6,6-[(3,3-dimethyl [I,I-biphenyl]-4,-4 diyl) bis(azo)] bis [4-amino-5-hydroxy-l ,3-naphthalene disulfonic acid] tetra sodium salt, usually called Evan blue (EB), to poly (N-vinyl 2- pyrrolidone) (PVP) in aqueous solution has been studied spectrophotometric ally at pH 9.2 in phosphate buffer in the presence and absence ofNaCI. Am •• = 606 nm for EB solutions was observed and then by the addition of PVP red shifted to 636 nm. Analysis of results by Scatchard and Hill methods showed a mixed cooperativity mechanism at different [PVPj. Thus at high [PVP] there is positive cooperativity in the conversion of weak to strong complex and negative cooperativity at low [PVP]. The V-shaped Scatchard plot at fixed [PVP] and varying [dye] further supplements the operation of positive and negative cooperativity.read more

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B AHMAD ,

Geochemical Characterization of Outcrop Sediments from Dharangi-Upper Indus Basin Pakistan

Three out crop samples from Dharangi area of Upper Indus Basin were investigated to determine hydrocarbon composition, thermal maturity, type of organic matter and generative potential. TOe values determined by both wet combustion titration and pyrolysis methods suggest good to excellent source rock potential for sediments namely B and e, whereas these values show marginal to fair source rock potential for sample A. Rock-Eval pyrolysis was carried out in order to determine maturity, type of kerogen and potential to generate liquid or gaseous hydrocarbons. Which suggest that samples A and B contain type ill kerogen and is gas prone; while sample e shows excellent accumulation of free and pyrolyzable hydrocarbons. It contains type II kerogen and is oil prone.read more

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M S YOUSAF ,T FAZEELAT ,

Precipitation Effect on Mg2+ Ions Sorption by FePO4

Potentiometric titrations of FePO. in the presence of Mi+ were carried out under different experimental conditions. The precipitation of Mi+ ions in the absence of FePO. was measured potentiometrically as a function of concentration, pH and temperature. The shift of the titration curves at a given temperature in the presence of exchanger (FePO.) is related to the metal ions adsorption at pH values below the plateau formation in the titration curves. It was found that the process of uptake of the Mg2+ changes from adsorption to precipitation with the increase in concentration, pH and temperatureread more

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S MURTAZA ,B DILHARA ,A NAEEM ,S MUSTAFA ,A HAMID ,

Effect of pH, Temperature and Time on the Stability of Potassium Ethyl Xanthate

Stability of potassium ethyl xanthate is studied as a function of time, temperature (283 and 300 K) and pH (5,7 and 9). The rate of its decomposition is found to decrease from 2.099 % to 0.451 % with the increase in pH from pH 5 to 9 at 283 K, while it is found to increase from 0.902 % to 4.103 % at pH 7 when the temperature is increased from 283 to 300 K. The maximum rate of decomposition is found to be 6.484 % at 300 K, which is reduced to 2.099 % at 283 K at pH 5read more

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S MUSTAFA ,Q SULTANA ,A NAEEM ,A HAMID ,

Flow Injection Procedure for Determination of NAD+ Using Immobilized Enzyme with Spectrophotometric Detection

A flow injection spectrophotometric method is described for the determination of NAD+ based on the production of NADH using immobilized alcohol dehydrogenase (ADH) isolated from Baker's yeast. The absorbance was monitored at 340 nm. The limit of detection (2 x standard deviation of the blank) was 0.01 mM with sample throughput 60 h-I. The calibration graph was linear in the range 0.2 - 1.0 mM, with relative standard deviation (n = 3) in the range 0.7 - 1.2%. Phenolic resin was used as a support for ADH immobilization and the  enzyme activity was maintained for three months.read more

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M YAQOOB ,L RISHI ,A NABI ,M MASOOM YASINZAI ,

Synthesis and CharacterizatiOllof Organosilicon Substituted Fluorenyl Derivatives

Friedel-Crafts cycloalkylation of biphenyl with 2,3-dichlorobutyltrichlorosilane (ChSi-CH2CHCICHCICH3) at a temperature of loo·C in the presence of anhydrous aluminum chloride catalyst gave cyclized product, 9-methyl-9-(2-trichlorosilylethyl)fluorene 1 a, in 33% yield. Methylation of la with nucleophilic reagent such as methyl magnesium chloride, gave 9­Methyl-9-(2-trimethylsilylethyl)fluorene 2 while bromination of 2 with excess amount of bromine in DMF resulted in 2,7-dibromo-9-methyl-9-(2-trimethylsilylethyl)fluorene 3 in good yield. All the compounds were structurally identified by GCIMS, 'H and 13C-NMR spectroscopy.read more

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S A KHAN ,

Dependence of Ionization Constants of Ephedrine in Aqueous and Non - aqueous Media

: Ionization constants of ephedrine are measured at different temperatures (25,30,35, 40,45 & 50Ge ) and in mixed organic-water solvent mixtures (dioxane-water, acetic acid-water, ethanol-water, methanol-water, acetonitrile-water and propylene carbonate-water) at 25GC. Data were obtained for the dissociation of ephedrine with particular emphasis on the effect of temperature and nature of solvent on pkt, values, Potentiometric data obtained were analysed by computer program. Results shows that as temperature increases, pkt, values decreases. Also pkb values are higher in mixed solvent systems than in aqueous media.read more

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SAEED UDDIN ,A W K KHANZADA ,

Fatty Acid Composition of Lipid Classes of Nelumbo nllcifera Seed Oil

The Nelumbium Nucifera seed oil (3.62%) was examined for their fatty acid composition. The oil was extracted from the ground seeds with a solvent mixture of chloroform and methonal (2:lv/v) and its different physil;ochemical values were evaluated. The oil was resolved by thin layer chromatography into hydrocarbon (0.58), wax ester (7.68%), triglycerides (60.54%), free fatty acids(l 9. 17%), 1,3 diglycerides (1.04%), monoglycerides (3.05%) by using hexane,diethyl ether and acetic acid(80:20:2 v/v/v) solvent system.The %age of polar lipids in the oil was(6.68%). Tho oil and its lipid fractions except hydrocarbon were converted into methyl esters and analyzed for their fatty acid composition by application of gas chromatography.read more

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A WAHEED ,S HAMED ,I KHOKAR ,H AKHTAR ,

Nitrations Using Metals Nitrates-Trifluoroacetic acid System

nitrations of halobenzenes with metal nitrates in bifluoroacetic acid at 9O"C have been carried out successfully.read more

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M A MUNAWAR ,M KHALID ,

Phytochemical Studies of Haloxylon recurvum

Seven compounds have been isolated for the first time from Ha/oxy/on recurvum namely, octadecanoic acid (I), octacosonic acid (2), I-triacontanol (3), triacontanoic acid (4), ~-sitosterol (5), ursolic acid (6) and ~-sitosterol 3-0-~·D·glucopyranoside (7). Their structures have been elucidated by ElMS, HREIMS, FAB, HRFABMS, IH and 13C NMR spectroscopic methodsread more

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N RIAZ ,E AHMED ,A MALIK ,A SHArif ,