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A study of the absorption spectra of the food colourants Tartrazine (E-102), Amaranth (E-123) and Curcumin (E-100) in various organic solvents and pH media, have been carried out. In addition, the spectral behaviour in aqueous micellar systems of anionic, cationic and non-ionic surfactants, as well as β-cyclodextrin, was investigated. Analytical methods are proposed for the determination of the...
A method for the determination of lead in human hair slurries by electrothermal atomic absorption spectrometry was optimized. Particle size reduction was achieved with a vibrational mill ball equipped with zirconia cups, 20 min being sufficient grinding time to achieve an adequate particle diameter (< 1 μm). The use of different thickening agents, namely glycerol, Triton X-100 and Viscalex HV30,...
The objective of the present work was the evaluation and characterization of a glassy carbon (GC) electrode modified by a bilayer lipid membrane (BLM) with incorporated single-stranded deoxyribonucleic acid (ss DNA). Various procedures were developed and tested for the incorporation of ss DNA at the electrode modified by the lipidic membrane:1. formation of self-assembled BLMs over ss DNA adsorbed...
A polarographic method has been applied to the study of the mixed-ligand system Zn(II)-glycine-glycinate, in aqueous medium, at I = 1.0 M (NaClO 4 ) and 25 ± 0.05°C. The study of the quasi-reversible waves characteristic of Zn(II) has been carried out by means of a new method of analysis proposed by the authors, which is faster and more accurate than the traditional methods. The stabilization...
A method has been developed for the modification of a carbon fiber microcylinder electrode with acylation. The stability and surface coverage of the Toluidine Blue O-modified microelectrode were studied by cyclic voltammetry. The modified electrode showed significant activity for the electrocatalytic oxidation of NADH in pH 6.8-7.8 solution. The catalytic current increased linearly with increasing...
A matrix modifier composed of platinum and nickel is proposed for the determination of selenium in a wild fruit juice made from Lantingguo (Vuccinium uliginosam). Five matrix modifiers (copper/nickel, palladium/magnesium, platinum/magnesium, platinum/nickel and platinum/copper) for suppressing the interference effects of seven co-existing elements (potassium, phosphorus, calcium, magnesium, manganese,...
Complexation of the Tl + , Pb 2+ and Cd 2+ ions with macrocyclic ligand 18-crown-6 (18C6) was studied in various binary solvent mixtures of propylencarbonate (PC)/dimethylformamide (DMF) and acetonitrile (AN)/dimethylsulfoxide (DMSO) systems at 22°C using the differential pulse polarographic technique. The stoichiometry of the complexes was found to be 1:1 and the...
Acid-base equilibria in aqueous solutions of cis-bis(trimethylphosphine)platinum(II) dinitrate at 25°C, 0.2 M ionic strength (KNO 3 ), have been investigated by potentiometry with a glass electrode. The procedure consisted of multiple addition of the investigated analyte to a supporting electrolyte solution ( multiple sample addition ) and subsequent titration with strong base. For the...
A new ligand capable of producing calcium-selective electrodes with excellent characteristics is presented. The ligand (1) is a calix[4]arene bearing phosphine oxide ligating groups on the lower rim and this is the first report that such ligands can discriminate in favour of calcium ions against magnesium ions and the alkali metal ions. This calcium selectivity is in complete contrast to the behaviour...
Quantitation of selenium in plants, soils and sludges was achieved by isotope dilution-mass spectrometry using a benchtop instrument. Samples for analysis were spiked with 76 Se isotope solution. Plant material was digested on a heating block at 150°C using a mixture of nitric acid and hydrogen peroxide. Selenium in soils and sludges was released by treatment with nitric acid followed...
This paper presents a method for the determination of the plant growth regulator β-naphthoxyacetic acid (NOA) by micellar-stabilized room temperature phosphorescence with the surfactant Triton X-100 (TX-100) as the micellar medium, thallium nitrate as the heavy atom and sodium sulphite as the oxygen scavenger. A multivariate optimization approach using the blocked cube star design of central composite...
Novel reagents and the rapid technique were developed for the simultaneous determination of water and ene-diols or thiols in chemical products, drugs and other materials which are inaccessible for direct K. Fischer titration. The reagents consist of iodine, tetramethylammonium iodide or potassium iodide, base (diethanolamine, triethanolamine, sodium acetate and/or urea) in methanol mixed with N,N-dimethylformamide,...
A new selective open tubular capillary gas chromatographic method is developed for the determination of trace amounts of piperazine. Piperazine is extracted from pharmaceuticals into cyclohexane and is partitioned with water. The aqueous solution is then injected into a 5% crosslinked Ph-Me silicone column programmed at 50-180 °C for 10 min. Piperazine is eluted after 3.18 min under isothermal...
The extraction behaviour of thorium(IV) from aqueous nitric acid employing 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) in the presence of tri-n-octyl phosphine oxide (TOPO) as well as tri-n-butyl phosphate (TBP) in xylene medium was investigated. The extraction constant (log k ex ) for the binary organic phase species Th(PBI) 4 was determined to be 8.26 which is by far the largest...
A remote electrochemical sensor for field monitoring of hydrazine compounds is described. The new submersible probe relies on the coupling of an effective electrocatalytic modified electrode to a 50 ft long shielded cable. The catalytic surface, based on an electorpolymerized film of 3,4-dihydroxybenzaldehyde, offers low-potential detection of hydrazine compounds. Such catalytic activity results...
2-pyridinecarbaldehyde-5-nitro-pyridylhydrazone (2PC-5NPH) was synthesized and its application in the spectrofluorimetric determination of Fe(III) ions in the presence of surfactants was examined. An emission peak of 2PC-5NPH, which increased remarkably by the addition of Fe(III), occurs at 420 nm upon excitation at 300 nm, and allows for the sensitive, selective determination of the ferric ion in...
The speed and efficiency of instrumentation for chemical analysis has improved dramatically over the past twenty years. Until recently, however, methods of sample preparation had not changed to keep pace, so this had become the slowest step in analytical chemistry methodology. The widespread adoption of domestic microwave ovens during the past twenty-five years has eventually led to their usage...
The coupling of sequential injection with inductively-coupled plasma mass spectrometry as an analytical tool for trace element detection is described. The technique is applied for determining the concentrations of lead, nickel and vanadium at part per billion levels in sample solutions of Saudi arabian crude oils. A microemulsion crude oil sampling procedure and a standard addition method using...
Phase inversion (PI) cellulose acetate membranes were cast on glassy carbon electrodes from a solution containing acetone as solvent and aqueous magnesium perchlorate as pore former. It is shown that a significant improvement of the reproducibility and permselective properties of the membrane is obtained by allowing complete evaporation of the solvent in a controlled humidity environment before the...
The suitability of composite graphite-poly(tetrafluoroethylene) (Teflon) electrodes as amperometric indicator electrodes in HPLC detection is demonstrated. The determination of the fungicides thiram and disulfiram in the presence of ziram has been chosen as an analytical problem. The optimization of working conditions, such as the choice of the organic solvent used in the mobile phase as well as...
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