Khalid Masud

A thermal analysis study of 1,2-dipiperidinoethane complexes of cobalt, nickel, copper, zinc and cadmium by TG-DTG-DTA techniques

A number of complexes of the general formula ML(NO3)2, (M=Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); L=1,2-dipiperidinoethane (DPE)) were prepared and studied by means of TG–DTG–DTA techniques. Their compositions were investigated by elemental analysis in order to ensure their purity and structural elucidations were based on conductivity measurements. room temperature magnetic measurement, proton NMR, and IR spectra. Thermal decomposition of these distorted tetrahedral complexes and their ligand took place in two distinct steps upon heating up to 720°C with the loss of inorganic and organic fragments and show almost the same mode of decomposition. The thermal degradation of all the complexes in static air atmosphere starts at temperature lower than observed for free ligand degradation. The composition of intermediates formed during degradation was confirmed by microanalysis and IR spectroscopy. The residues after heating above 600°C correspond to metal oxide. It follows from the results that thermal stability of the complexes increases in the following sequence: Ni(II)

Thermal degradation of glycidyl methacrylate-styrene copolymers

Abstract The thermal degradation of copolymers of glycidyl methacrylate and styrene was studied by thermal volatilisation analysis (TVA), thermogravimetry (TG) and pyrolysis mass spectrometry. The apparent activation energies for the decomposition of copolymers were calculated from the results of TG experiments. The condensable volatile products from the TVA experiments have been identified after separation by subambient thermal volatilisation analysis (SATVA). The cold ring fraction was examined by IR spectroscopy. The copolymers are intermediate in stability between polystyrene and poly(glycidyl methacrylate). The degradation products are mainly those expected by comparison with those obtained from the homopolymers. A mechanism of thermal degradation has been suggested.

The thermal degradation of poly(allyl methacrylate)

The thermal degradation of poly(allyl methacrylate) has been investigated using thermal volatilisation analysis (TVA), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The main pyrolysis products have been identified and the characteristics of the reactions deduced and discussed. Mechanisms have been proposed to account for the products formed.

Comparative study of selected essential and non‐essential metals in various canned and raw foodstuffs consumed in Pakistan

Levels of selected essential metals (Cu, Fe and Zn) and non‐essential metals (Cd and Pb) were determined by the wet digestion based atomic absorption flame spectrophotometric method in twenty canned foodstuffs of local and foreign origin. The study revealed that on average, the concentrations of Fe, Cd and Pb in local foodstuff were more than those found in imported canned products. The contents of Fe and Pb in local canned food were almost double that of the counterpart imported versions. Analysis of the construction materials of the tins indicated that some metals, such as Pb, had levels twice as high as those found in the foreign tin containers. The results showed that the Cu concentration in various foodstuffs ranged between 0.04 and 8.88mg/kg, Fe between 3.07 and 126mg/kg, Zn between 0.19 and 22.8mg/kg, Cd between 0.15 and 1.16mg/kg and Pb between 0.11 and 2.04mg/kg. The results are compared with the levels of metals in corresponding data from the literature.

Thermal degradation of blends of phenyl methacrylate–styrene copolymers with aluminium ethoxide

Abstract The thermal behaviour of phenyl methacrylate–styrene (PMA–ST) copolymers was studied in the presence of aluminium ethoxide [Al(OC 2 H 5 ) 3 ]. The blends were investigated in an inert atmosphere using thermogravimetry–differential thermogravimetry (TG–DTG) and under vacuum using thermal volatilisation analysis (TVA). The condensable volatile degradation products from the TVA experiments were separated by sub-ambient TVA and characterized by IR spectroscopy and gas chromatography–mass spectrometry (GC–MS) techniques. The degradation products from blends contained some additional products and it was found that the course of degradation had been changed in the presence of Al(OC 2 H 5 ) 3 . Mechanisms have been proposed for the formation of new products.

THERMAL DEGRADATION BEHAVIOR OF BLENDS OF PHENYL METHACRYLATE-STYRENE COPOLYMERS WITH ALUMINUM ISOPROPOXIDE

Thermal degradation studies were carried out of copolymer phenyl methacrylate-styrene in the presence of aluminum isopropoxide to assess the stability and alteration of degradation mechanism using thermogravimetry-differential thermogravimetry (TG-DTG) in inert atmosphere and under vacuum using thermal volatilization analysis (TVA). After collecting the condensable volatile degradation products from TVA experiments and separating them by sub-ambient TVA, investigation and identification were effected out by IR spectroscopy and gas chromatography-mass spectrometry (GC-MS) techniques. The degradation products from the blends consisted of some additional products, i.e., isopropanol, phenol, methacrylic acid, ethyl benzene, benzene and a cyclic compound apart from similar products obtained from the degradation of pure copolymers. The mechanism of newly formed degradation products has been discussed in detail.

Selected toxic metal levels in seasonal fruits of Pakistan

Levels of selected essential and non‐essential metals (Cd, Cr, Pb, Cu, Fe and Zn) and those of macro‐nutrients (Ca, K, Mg and Na) are estimated in 15 different seasonal fruits available in local Pakistan markets. The wet digestion oxidation method was used for the analysis of samples by the flame atomic absorption technique. The results indicated almost 100 percent incidence of occurrence of trace metals and macro‐nutrients in all fruits. The highest concentration was observed for zinc, ranging between 0.13 and 79.9mg/kg, wet weight, respectively for banana and mango. The iron levels ranged from 0.55 to 44.8mg/kg, wet weight, for pomegranate and mango. The concentrations of Cd, Cr, Pb and Cu remained at marginal levels, except for certain fruits where the concentrations were very high. The data are compared with allowed safe limits laid down by WHO.