VOLUME 27, NO1, FEB 2005

Light Scattering Studies of poly (methyl methacrylate)(PMMA) in Different Solvents

Unfractionated and fractioned samples of poly(methyl methacrylate) (PMMA) were chqrqcterized by static light scattering (SLS) and gel permeation chromatography GPC) techniques at room temperature  (33oC) in acetone and acetonitrile. Our results showed that the samples did not show any angular dependency. From static light scattering (Turbidity) measurements molecular weight (Mw) and second virial coefficients (A2) were determined. The positive value of A2 in case of acetone show that acetone is good solvent for PMMA while the A2 Values for accetonitrile show that accetonitrile is a theta solvent. The light scattering results are in consistent to that of GPC results, (conduced at Aberdeen University UK).read more

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A SAEED ,B MOHAMMAD ,K MAHMOOD ,

Air Quality in the Atmosphere of Karachi City – An Overview

A study on the measurement of concentration of major components in the ambient air was carried out at five different stations in Karachi city and data was collected for O3, SO2, CO, NO and NOx along with the meteorological parameter. The data generated has been evaluated for Time Weighted Average (TWA) values. The results suggest that all the pollutants were mainly due to the emission from industries, refineries, power generation plants and also from motor vehicles. Due to absence of regulatory laws/standards about ambient air quality in Pakistan; the results have been discussed with reference to the ambient air quality limits recommended by the World Health Organization.read more

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D R HASHMI ,G H SHEIKH ,T H USMANI ,

Hydro Liquefaction of Pakistani Coal in Benzene Yields of Liquefied products as function of operating as function of operating Conditions

Degari coal was liquefied in a micro reactor in benzene Yields of liquefied products as a function of operating conditions were calculated. Liquefied was performed under varying conditions of temperature, hydrogen pressure, residence time , coal/solvent ratio and coal particle size. Maximum conversion of the coal understudy to liquid product has been observed at temperature of 400cC, residence time of 1 hour, hydrogen pressure (cold) of 15kg/cm3, coal/solvent ratio of 1:2 and coal particle size of 250-212 um. Benzene proved to be effective solvent for obtaining reasonable yields of liquefied products.read more

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I AHMAD ,

Fluorescence Studies of Polystyrene in Different Solvents

This investigation was done to have a systematic study of the Fluorescence of Polystyrene polymer with respect to concentration and solvent. A wide range of concentration was selected for fluorescence studies and four different solvents i.e 1,2 –Dichloroetahane. Cyclopentane.   n-Butylaccetate and Cyclohexane were employed for this work. The fluorescence peak at 335 nm was selected to be due to excimer emission while the peak at 283 (or 286) nm was selected to be due to monomer emission, and the excimer and monomer intensities were measured at these wavelengths for all the solvents under investigation. The R values (i.e.  lE/lM ratio) were found for all the solutions and were found to increase with concentration. This increase is though to be due to several effects including intermolecular excimer formation. Remote adjacent intramolecular excimer formation, coil contraction and soon . the R Values remarkably depends upon nature of solvent. The fluorescence emission intensity ratio (lE/lM) is in the order of n-butyloacetate <1,2-Dichloroethane <Cyclohexane <cyclopentane. R is shown to be higher in poor solvent while is low in good solvent.  read more

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M S KHAN ,S A KHAN ,Y IQBAL ,W KHAN ,

SnS Thin Films fabricated by Normal Electrochemical Deposition on Aluminum Plate

SnS thin films were deposited onto aluminum sheet through electrochemical deposition (ECD) from aqueous solution containing SnSO4 and Na2S2O3. SnS deposited was polycrystalline and orthorhombic structure, and its composition was S-rich in acidic pH while Sn-rich at higher Ph values. The relationship between film properties on the deposition parameter was investigated to optimize the decomposition condition.read more

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M I ZAMAN ,S KHAN ,L K KHEL ,

Kinetics of the Gas-phase Thermal Decomposition of Methylcyclopropanemethanol

Kinetics of gas phase thermal decomposition of Methylcyclopropanemethanol (MCM) was studied over the temperature range 640-720 K and pressure between 4-16 torr using static system. Initial runs carried out in aged unpacked reaction vessel; yield small amount expected isomerization products i.e. cis and trans-2-methyl-1-buten-4-ol and 2-methy-2-buten-1-ol. Formed simultaneously with the isomeric products were large amount of other products that have clearly formed as the result of fragmentation reactions. In view of the complexities due to rapid secondary decomposition of initial reaction products it was decided only to determine the overall rate loss of methylcyclopropane methanol; this proved to be a first order, homogeneous, unaffected by the addition of nitric acid and probably unimolecular. First order rate constants were determined at six temperatures using 1.5 torr initial reactant. The Arrhenius parameters are given in the rate equation. K(totsl/s-1 =1014.8±1.7 exp(-248.2±12.1kj mol-1/RT) The results are compared with those for other cyclopropanes and mechanism considered likely to involve a biradical transition stateread more

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I A AWAN ,M ALI ,T MAHMOOD ,

Quantitative and Qualitative Determination of Temazepam in Pure and Pharmaceutical Samlples by first Order Derivative Spectrophotometry

A new improved first order derivative spectrophotometric method is developed for the simultaneous determination of Temazepam in pure and pharmaceutical samples. Absolute alcohol is used as a solvent through out the study. Temazepam reacts with 0.01% alizirine to give a red-purple colour complex having maximum absorbance at 521.9nm. the colour reaction obeys Beers Law from 4.0-200.0mg/ml of temazepam. The correlation coeffincient is 0.99 and relative standard deviation is 0.84%. the quantitive assessment of tolerable amount of other drugs was also studied. The proposed method can be successfully applied for the quality control of pure tempazepam and in pharmaceutical dosage. This method is simple, reliable and reproducible.read more

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N YAQOOB ,S I KHAN ,M A KASHMIRI ,

Spectroscopic Determination of Essential Elements in Unpolished Rice (Oryzab sativa L.), Grown at RRI, Dokri

Seven rice varieties collected from, rice research institute (RRI) Dokri, sindh in Pakistan. Agricultural soil samples were also collected to evaluate the bioavailability of eight essential elements to seven varieties of rice grown in same agricultural plot. The agricultural soil and rice varieties were digested by wet acid digestion method. Homogeneity of the prepared materials was evaluated through the determination of eight essential elements i.e. Na, K, Mg, Ca, Fe, Mn, Zn, using frame atomic absorption spectrophotometer. The unpolished rice varieties contained high amount of essential micronutrients such as Na, K, Mg, Ca, Fe, Mn, Zn, and Cu (616.01, 4097.15, 2626.20, 73.90, 1829.88, 50.34, 42.72 and 7.21mg/kg) in seven different varieties of rice i.e. DR-82, DR83, DR92, DR92, Kanwal-95, Lateefi sadayat and sarshar respectively.read more

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G Q SHAR ,S A ARAIN ,S SAHITO ,L A SHAR ,T G KAZI ,

The Contents of Fifteen Essential, Trace and Toxic Elements in Some Green Tea Samples and Their Infusion

The content of fifteen elements i.e. Ca, Mg, Na, K, Fe, Mn, Zn, Co, Cu, Cr, Ni, Pb, Cd, Ba and Al were determined for 30 samples from three types of green tea samples using flame atomic absorption spectroscopy. The samples were purchased from authentic tea dealer in Peshawar imported from India, China and Kenya. However, some samples were taken which were locally produced in Pakistan with branded packing and without package. The NBS tea leaves. The wet digestion and infusion procedure reference material was also analyzed simultaneously with tea samples. The wet digestion and infusion procedures were also employed for determi8nation of total and aqueous extracted elements are elements are present in total in tea infusion. The levels of toxic metals are low but levels of aluminum are high in both forms. The results obtained form this analyzed have shown good accuracy and reproducibility. The relative error and relative standard deviation were less than 19% for most of the elements analyzedread more

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T G KAZI ,G H KAZI ,M A JAKHARANI ,Q G SHAR ,S SHAIKH ,

Spectral Interference and Line Selection for Trace Element analysis in a Multi-Component Matrix Using Inductively Coupled Plasma Atomic Emission Spectroscopy

Environmental samples like waste waters are generally known to contain calcium, magnesium, sodium and potassium as major constituents. It is important to assess the amount of interference at analysis wave length arising from the matrix as well as other analyses to select suitable analysis lines. This paper report the measurement of partial sensitivities of 49 prominent lines of 17 impurities of interest in waste water (Ag, Al, As, B,, Ba, Be, Cd, Co, Cr,Cu, Fe, Hg, Mn, Ni, Pb, V, Zn) using indecisively coupled plasma atomic emission spectroscopy. Spectra scans for 300 pm wide windows centered (± 150pm) around analyses wavelengths, were obtained under compromise operating conditions. Using the criterion of “true detection limit”..Q–values for line interference [QIJ(la)] and Q-values for wing background inference [QWJ(Dla)] due to Ca, K, Mg and Na have been worked out. The Q-value s give a quantative estimate of the extent of spectral inference and thus permit a rational selection in a multi-component matrix is more complex than in a single element matrix. Therefore, prior quantitative knowledge of the matrix elements is inevitable for selection of a suitable line for trace element analysis. Trace element analysis in synthetically prepared samples indicates the presence of non-spectroscopic matrix effects.read more

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S QAMAR ,A A GHAZI ,M A ATTA ,