VOLUME 22, NO1, MAR 2000
12
 
Determination of Dissociation Constants and Thermodynamic Parameters of 8-Aminoquinoline by Potentiometry in Aqueous and Mixed Organic-Water Solvent Systems

A W K KHANZADA ,HAFIZ A BARI INDHAR ,

The dissociation constant (pK4) and thermodynamic parameters (pK4) of 8-­aminoquinoline are determined in aqueous and in mixed organic-water (dioxane, EtOH and MeOH) solvent systems. It is observed that ionization constant of 8-aminoquinoline in aqueous system increases with the increase of temperature. The curve is a parabolic one. It is to be noted that pK4 values of this compound are lower than those of quinoline and some of its amino derivatives. For mixed organic-water solvent systems pK4 M and pKaT values versus percent composition decrease slowly with increase in percent of EtOH, MeOH and dioxane. The curve of the pK. versus percent composition is a distorted parabola.The data have been obtained potentiometrically by titrating aqueous 8-aminoquinoline solution with hydrochloric acid. The values of dissociation constant were obtained from these data by a computer program written in OW-BASIC. From pK. values Gibb's free energies (DG) have also been calculated.
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Levels of Cr, Cu, Fe, Pb and Zn in Water-based Paints Manufactured in Pakistan

M A RAUF ,M IKRAM ,M JAFFAR ,

The levels of four selected toxic elements; namely, chromium, copper, iron and zinc in various brands of water-based paints manufactured in Pakistan are reported. The analysis was done using the Flame Atomic Absorption Spectrophotometric method. The concentration of iron was especially high in all the paints under investigation. 
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Pre Concentration of Impurities in Gaseous Uranium Hexafluoride and Their Characterisation by Mass Spectrometry

M A ATTA ,AQIL KHAN ,A R FAROOQUI ,

Distillation is normally used to remove more volatile impurities from uranium hexafluoride. Here this method of distillation was applied to natural uranium hexafluoride samples to pre concentrate those impurities which are leas volatile than UF 6. Mass spectra were obtained from "pre concentrated" samples using a quadrupole mass spectrometer and were compared with those of "original" samples. The mass spectra were found to be complex due to the formation of different UF6 daughter ions during ionization process which in some cases also interfere with the impurity peaks. After pre concentration process the fluorides of Cr, Ta. Ir, Rb, Ti, Si, Sr and Rh were identified. Many organic impurities were also found in the sample. 
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Thermoanalytical Studies of Some Schiff Base Polymers and Their Metal Chelates

S W SHAH ,M Y KHUHAWAR ,A H CHANNAR ,

Thermogravimetry (TO) and differential thermal analysis (DTA) of poly S,S·· methylene·bis.salicylaldehyde-tetramethylenediimine (PMSATen). poly S,S' -methylene-bis­salicylaldehyde-meso-stilbenediimine (meso-PMSAS). poly 5, 5'-methylene-bis-salicylaldehyde­dl·stilbenediimine (dl·PMSAS). Poly 5, 5.methylene-bis-salicylaldehycle-2.6-diiminopyridine (PMSAP), and their copper (II) and nickel (II) chelates were recorded in nitrogen atmosphere upto 800 °C. Loss in weight occurs in two to three stages. The polymers and their nickel chelates indicate better thermal stability as compared to their corresponding copper complexes. DT A shows a series of endotherms with maximum in the range of 400-700 °C. 
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Synthesis and FTIR Spectra of the Complexes of Tumor Cell Differentiating Agent Hexamethylene Bisacetamide with Metal (II) Halides

DAVID M L GOODGAME ,MARGARET GOODGAME ,IZHAR HUSSAIN ,

The syntheses are reported of a number of complexes of  tumor cell differentiating agent Hexamethylene bisacetamide (HMBA) with group II metal halides. These complexes have been characterized by elemental analyses. The FTIR spectra of all these complexes as well as those of previously repor1ed Nickel (II). Manganese (II) and Cobalt (II) complexes [1-3 J have been measured and the mode of coordination of ligand has been established. In all of these complexes, the HMBA molecules have been coordinated with the metal ions through their carbonyl oxygen atoms. 
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Verification of A Tear Gas and A Pesticide At Trace Levels in A Water Sample

IMTIAZ AHMED ,

Tear gas like CR and pesticide Malathion present at trace level in a water sample has been analyzed by gas chromatography and liquid chromatography techniques. Solid phase extraction method was used for extraction of suspect agents from water samples. Retention Index monitoring method was applied for identification. Mass spectrometry was used for verification of suspect agents.
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A Physicochemical Approach to Interpret the Biological Activities of some Dipeptide Systems

KH ME HASHEM ,MA T IBRAHIM ,FA EA ALI ,

The biological activities for four-Iso-nicotinoyl dipepetide systems are attributed to some physiochemical parameters. The semi-empirical MNDO together with the AMI methods, were applied to define these parameters by optimizing the structural energy of the four systems with respect to incremental variation of their backbone dihedral angles. The lowest energetic structures are determined by generating two ECD maps by plotting j11 vs Y1I and Y1 vs +j11 dihedral angles for each of the four systems. The comparison between the lowest energetic structures reveals that these systems have permanent dipole moments. Based on the different susceptibilities of the dipeptide tails to rotate as bonded charged masses around the X-axis of the molecular frame, the Gaussian cylinders characteristic by nine different charged zones could be speculated. The sign of the residual charges on the zones corresponding to the backbone's bonds and side chain residues, which are labelled section 2, are determined as the required physicochemical parameters. It appears that the biological activity of each system is affected by the sign of the charges allocated on the above section of each system. If the charge is +ve then the corresponding dipeptide system(s) should posses biological activities, otherwise the system(s) are biologically inactive.
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Preliminary Biological Screening of Some Marine Algae Collected from Karachi Coasts of Arabian Sea

FRAN MAZHAR ,USMAN GHANI ,VIQAR UDDIN AHMAD ,MUHAMMAD SHAIQ ALI ,

The antibacterial assay using the ethanol extracts of the studied algae showed significant activity against bacteria while the water and chloroform extracts were found inactive. Most of the algae showed very significant activity against Corynebacterium diptheriae and Staphylococcus anreus; The results of the antifungal assay showed that all the extracts i.e. Ethanol, chloroform and water extracts are capable to inhibit the growth of human, animal and plant pathogens. Most of the extracts showed inhibitory activity, however few of the extracts were found to promote the growth of certain fungi. The ethanol extracts of the most of the three classes of algae had antifungal activity against human pathogens. An interesting observation was made regarding the ethanol, chloroform and water extracts of lyengaria stellata, all of which were found active against animal pathogen Microsporum canis. From all the algae tested, the ethanol extract of Codium iyengarii showed Wry significant antifungal activity against all types of pathogens. The brine shrimp lethality bioassay showed that most of the ethanol, chloroform and water extracts were active but the LD~ values of most of the extracts were higher than 1000 f.1WmI. The ethanol extracts of green algae did not show significant results. The water extracts of the three classes of algae were active at higher doses. The results of the Lemna bioassay showed that some of the ethanol extracts of the algae inhibit while others help to promote the growth of Lemna aequinoctiatls welv. The water extracts of different alga were found to promote the growth of the tested plant A very interesting result was observed from the ethanol extract of Sargassum teneriumum which gave 100 % inhibition of the fronds at highest concentration i.e. 500 ppm. Among the chloroform extracts the most active was the chloroform extract of green algae Codium iyengarii. This extract significantly inhibited the growth in all three concentrations. From all the algae tested for the phototoxic activity, the extracts (ethanol, chloroform and water) of brown alga lyengaria stellata were found to inhibit the growth of the fronds while the extracts (ethanol, chloroform and water) of the red alga Melanothamnus somalensis promoted the growth of L aequinoctiatls.
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The Separate and Combined Effects of Copper and Cadmium on the Survivorship of Penaeid Shrimps

Y Q SU ,SJ LI ,A B MUNSHI ,

Critical survival rate for all larval stages of penaeid shrimp was determined using static bioassay with copper, cadmium and their I: I mixture. The lethal concentration (24 h LC50) was 200 mg/l of Cu. 250 mg/l of Cd and 300 J.LS'L of mixture in average for all larval stages along with slight variation at every stage (Nauplii- Myses III) in Penaoul monodon LC50 was 400 mg/l. In Penaeul -nicillatul LC,o the values were found to be 200 mg/L of Cu, 230  of Cd and 250 mg/L for mixture in Nauplii to Myses however for postlarvae the LC,o was within the same as in Penaeul monodon. The estimation of survival rate within 24·48 h under lethal and acceptable concentration of copper and cadmium showed culturing farmers at most productive and safe condition of their ponds.
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Commercial Extraction of Gel from Aloe vera (L) Leaves

NUSRAT SHAFI ,GUL AKHTAR KHAN ,LAJBER KHAN ,

A commercially viable process for preparing a stable and pharmalogically active crystalline substance from the fresh whole leaf meal has been developed. Dermatological testings of the product on experimental animals and volunteers have shown promising wound healing remedy for all kinds of damaged skin conditions.
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