M. A. H. Hafez

Preconcentration and separation of total mercury in environmental samples using chemically modified chloromethylated polystyrene-PAN (ion-exchanger) and its determination by cold vapour atomic absorption spectrometry

The use of chemically modified chloromethylated polystyrene-PAN, CMPS-PAN (ion-exchanger) for the preconcentration and separation of total mercury after digestion in preparation for determination by cold vapour atomic absorption spectrometry (CVAAS) was described. The effects on the percentage of recovered mercury by mass change of ion-exchanger, stirring time, pH of the solution samples and eluent concentration were studied. The distribution coefficient K(d) is 10(6.6) ml g(-1). The interfering effects of some foreign ions were described. The metal complex formed between CMPS-PAN ion-exchanger and mercury was characterized by IR spectroscopy, pH-metric titration and thermal analysis. The method is simple and rapidly applicable for the determination of total mercury (ng ml(-1)) in natural water, milk and urine.

Spectrophotometric and complexometric methods for the determination of thorium and fluoride using bromocresol orange reagent

The ternary purple coloured complex formed between Th(4+), bromocresol orange (BCO) and cetylpyridinium bromide (CPB) in acidic medium was investigated spectrophotometrically. Results obtained revealed the formation of 1:1:1, Th:BCO:CPB complex in aqueous solution at pH approximately 0.5 with a logarithmic conditional stability constant of 12.04+/-0.1, I=0.1 at 25 degrees C. The colour of the ternary complex was used for the determination of thorium(IV) in the range of 0.02-2.6 mug ml(-1) Th(4+), =9.2x10(4) l mol(-1) cm(-1) at 560 nm. Beside its high sensitivity, the reaction was also proved to be highly selective for Th(4+). Thorium(IV) was determined in presence of great number of transition metal ions, rare earths and different anions. Th(4+) was also determined with high accuracy and precision by its titration with disodium ethylenediaminetetraacetate (Na(2)EDTA) using BCO as an indicator at pH approximately 0.5. The endpoint was detected either visually or spectrophotometrically (lambda=550 nm). The proposed procedures were successfully applied for the determination of Th(4+) in standard Th-U ores and in a series of naturally occurring ores or minerals containing thorium. A spectrophotometric method was also described for the determination of fluoride ion, which was based upon the decrease in colour intensity of the Th-BCO complex on mixing it with F(-) ion. The proposed method was convenient, rapid and sensitive for fluoride. It could be used for the determination of fluoride ion in the 0.02-3.00 mug ml(-1) range (S.D.+/-0.9%). The proposed method was successfully applied for direct determination of F(-) ion in water obtained from different origins and the results were satisfactory.

Electrochemical synthesis of benzoylglycine and ethylphthaloyl-glycine complexes of transition metal ions

SummaryThe direct electrochemical oxidation of metallic iron, cobalt, nickel and copper in Me2CO solution of benzoylglycine and/or ethylphthaloylglycine gave products with high yields. For each of the complexes, the electrochemical efficiency is commensurate with the metals being divalent. Conventional physical and chemical studies were used to characterize the isolated complexes and octahedral geometry was suggested for them on the basis of magnetic and electronic spectral studies. The i.r. spectra show that the ligands coordinate in a bidentate fashion; the carboxylate ion is monodentate. The molar conductances agree with the complexes being non-electrolytes.

Study of the chromogenic reactions of semi-xylenol orange with rare earths and thorium

Abstract The composition, stability constants and molar absorption coefficients of the chelates of thulium, ytterbium, lutetium and thorium ions with Semi-xylenol Orange (SXO) are determined spectrophotometrically in a medium of hexamine, and chloroacetate buffer. In the thulium, ytterbium, lutetium and thorium-Semi-xylenol Orange systems, Tm(SXO), Yb(SXO), Lu(SXO) and Th(SXO) chelates are formed with logarithmic overall stability constants of 12.48±0.01, 12. 55±0.01, 12.94±0.015 and 22.16±0.01 and molar absorption coefficients of 2.22×104 (530 nm), 2.17×104 (532 nm), 2.25×104 (530 nm) and 3.33×104 (535 nm) dm3 mor−1cm−1 respectively. The precision and accuracy attainable in direct spectrophotometric titrations of the Tm3+, Yb3t, Lu3+ and Th4+ separately and the successive determination of each of the three rare earths and Th4+ ion with a 0.001 mol dm−3solutions of diethylenetriaminepentaacetic taacetic acid (DTPA) and PbC12 of the same concentration using Semi-xylenol Orange (SXO) as a metallochromic ind...

Some aspects of the preparation, characterization and thermal decomposition of anisaldehyde Girard T complexes of some transition elements

Anisaldehyde Girard T complexes of Mn(II), Fe(III), Co(II) and Cu(II) with the general formula [MCl2(AGT)2]Cl2 or [MCl2(AGT)]Cl, where (AGT)=anisaldehyde carbohydrazone methyltrimethylammonium cation, H3C-O-C6H4-CH=N-NHCOCH2N+-(CH3)3 andM=Mn(II), Co(II), Fe(III) or Cu(II) were prepared. Elemental analysis, electrical conductance and IR spectra showed that the ligand coordinates with the studied metals in keto form through the azomethine and carbonyl groups. The molar conductances, electronic spectra and magnetic moments of the solid complexes were determined. The processes of thermal decomposition of these complexes were studied. From the analysis of the thermal decomposition curves obtained, the corresponding kinetic parametersn, Ea and logA were evaluated by two different methods and the effects of the central metal ions on the stabilities of the complexes are discussed.ZusammenfassungEs wurde die Herstellung und Isolierung von Anisaldehyd-G-T-Komplexen von Mn(II), Fe(III), Co(II) und Cu(II) der allgemeinen Formel [MCl2(AGT)2]Cl2 oder [MCl2(AGT)]Cl durchgeführt, wobei (AGT)=Anisaldehydcarbohydrazon-methyl-trimethyl-ammoniumkation H3C-O-C6H4-CH=N-NHCOCH2N+-(CH3)3 undM=Mn(II), Co(II), oder Fe(III) und Cu(II). Elementaranalyse, elektrische LeitfÄhigkeit und IR-Spektren zeigten, da\ der Ligand an den untersuchten Metallen in der Ketoform, über die Azomethin- und Carbonylgruppe koordiniert ist. Es wurden die molare LeitfÄhigkeit, Elektronenspektren und das magnetische Moment der festen Komplexe bestimmt. Der Vorgang der thermischen Zersetzung dieser Komplexe wurde untersucht. Durch Analyse der erhaltenen thermischen Zersetzungskurven wurden die entsprechenden kinetischen Parametern, Ea und logA durch zwei verschiedene Methoden ermittelt und weiterhin der Einflu\ des zentralen Metallions auf die StabilitÄt der Komplexe diskutiert.

Comparative Analytical Determination of Thorium in Medium and Low-Grade Minerals and Ores Using Semimethylthymol Blue

Abstract The composition, stability constants and molar absorption coefficient of the chelate of thorium ion with Semimethylthymol Blue, SMTB is determined spectrophotometrically in a medium of perchloric acid and sodium perchlorate solution (pH 2.0). In the thorium-SMTB system, a purple red Th(SMTB) chelate is formed with logarithmic overall stability constant of 20.76±0.01 and molar absorption coefficient of 1.44x104 (560 nm) dm3 mol−1 cm−1. SMTB was proposed as a new reagent for the spectrophotometric determination of micro-molar amounts of thorium at γmax 560 nm. The colour development depends on time, temperature, pH and buffer species. The interferences of different anions, cations and organic acids on thorium determination were also investigated. Beers law was obeyed for 11.6–104.4 μg Th(IV)/25 ml(0.46–4.18 ppm). SMTB was used for the spectrophotometric determination of thorium in medium and low-grade minerals and ores and the results were reproduciable and satisfactory. Comparative study includin...

Thermal studies on anisaldehyde carbohydrazone methyl trimethylammonium chloride complexes of zinc, cadmium and mercury

AbstractThe kinetic parameters of the thermal decomposition of Zn, Cd and Hg(II) hydrazone complexes of the general formula [MCl2(AGT)2]Cl2, where AGT=anisaldehyde carbohydrazone methyl trimethylammonium cation,

Thermal decomposition of chloromethylated poly(styrene)-PAN resin and its complexes with some transition metal ions

CH_3 O - C_6 H_4 - CH = N - NH - CO - CH_2 - \mathop N\limits^ + (CH_3 )_3 ,