S. B. Salama

A sequential injection method for the determination of aluminum in drinking water using fluorescence enhancement of the aluminum-morin complex in micellar media

Abstract A robust and simple sequential injection (SI) method for the assay of aluminum ions in natural water is described. The method is based on the enhancement of the fluorescence of the aluminum–morin complex in the presence of a non-ionic surfactant (Tween-20). The fluorescence of the complex is monitored at an emission wavelength of 495 nm with excitation at 425 nm. The pH, morin concentration and the aspirated sample volume were optimized simultaneously using a chemometric method. The optimum operating conditions are: 150 μl aspirated sample volume, 20 μM morin concentration, a pH of 4.5 and 0.8% Tween-20. Using these optimum conditions a linear calibration curve was obtained from 50 to 1000 ppb. The detection limit was 3 ppb and the maximum relative standard deviation (n=5) of the method was 2.9%. The method was successfully applied for the determination of aluminum ions in natural water samples.

A sequential injection spectrophotometric method for the determination of penicillamine in pharmaceutical products by complexation with iron(III) in acidic media

A simple, robust and sensitive sequential injection spectrophotometric method for the assay of penicillamine (PA) in pharmaceutical formulations is developed. The method was based on the complex formation when PA is reacted with iron(III) solution in hydrochloric acid media. The deep blue colored PA-iron(III) complex produced is monitored at a maximum wavelength of 600 nm. A five level orthogonal array design coupled to genetic algorithm was employed to obtain the optimum experimental conditions for the determination of PA using peak absorbance as the measure of the systems performance criterion. A linear dynamic range for the determination of PA of 25-300 ppm was obtained with a sampling frequency of 50 h(-1) and a relative standard deviation of less than 0.98%. The method was successfully applied to the determination of PA in pharmaceutical formulations.

Chemiluminescence determination of chlorpheniramine using tris(1,10-phenanthroline)–ruthenium(II) peroxydisulphate system and sequential injection analysis

A sequential injection (SI) method was developed for the determination of chlorpheniramine (CPA), based on the reaction of this drug with tris(1,10-phenanthroline)-ruthenium(II) [Ru(phen)(3)(2+)] and peroxydisulphate (S(2)O(8)(2-)) in the presence of light. The instrumental set-up utilized a syringe pump and a multiposition valve to aspirate the reagents [Ru(phen)(3)(2+) and S(2)O(8)(2-)] and a peristaltic pump to propel the sample. The experimental conditions affecting the chemiluminescence reaction were systematically optimized, using the univariate approach. Under the optimum conditions linear calibration curves of 0.1-10 microg/ml were obtained. The detection limit was 0.04 microg/ml and the relative standard deviation (RSD) was always < 5%. The procedure was applied to the analysis of CPA in pharmaceutical products and was found to be free from interferences from concomitants usually present in these preparations.

Enhancement of the chemiluminescence of penicillamine and ephedrine after derivatization with aldehydes using tris(bipyridyl)ruthenium(II) peroxydisulfate system and its analytical application

A novel sequential injection (SI) method was developed for the determination of penicillamine (PA) and ephedrine (EP) based on the reaction of these drugs with tris(bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) and peroxydisulfate (S(2)O(8)(2-)) in the presence of light. Derivatization of PA and EP with aldehydes has resulted in a significant enhancement of the chemiluminescence emission signal by at least 25 times for PA and 12 times for EP, leading to better sensitivities and lower detection limits for both drugs. The instrumental setup utilized a syringe pump and a multiposition valve to aspirate the reagents, (Ru(bpy)(3)(2+) and S(2)O(8)(2-)), and a peristaltic pump to propel the sample. The experimental conditions affecting the derivatization reaction and the chemiluminescence reaction were systematically optimized using the univariate approach. Under the optimum conditions linear calibration curves between 0.2-24 microgmL(-1) for PA and 0.2-20 microgmL(-1) for EP were obtained. The detection limits were 0.1 microgmL(-1) for PA and 0.03 microgmL(-1) for EP. The procedure was applied to the analysis of PA and EP in pharmaceutical products and was found to be free from interferences from concomitants usually present in these preparations.

Weak complexes of sulphur and selenium. Part III. Effect of solvent on the stability of 1 : 1 complexes of sulphur dioxide, sulphinyl dichloride, and sulphonyl dichloride with halogen ions

The complex species SO2′X–, SOCl2′X–, and SO2Cl2′X–(X = Cl, Br, and I) have been studied in acetonitrile, dimethyl sulphoxide (dmso), and water (for SO2′X– species only). It appears that solvation of halide ions by dmso is important in deciding the stabilities of the different species.

Weak complexes of sulphur and selenium. Part 6. Stability constants of the weak 1 : 1 complexes of sulphur dioxide, thionyl chloride, and sulphonyl chloride with halide ions in the mixed solvent acetonitrile-dimethyl sulphoxide at 25 °C

The stability constants of SO2·X–, SOCl2·X–, and SO2Cl2·X–(X–= Cl–, Br–, or I–) have been determined spectro-scopically in different mixtures of acetonitrile and dimethyl sulphoxide as solvent. The values (at 25 °C) are not constant for different solvent mixtures. To account for this it is assumed that a number of interactions exist in these solutions, and of these solvent-solvent interactions are believed to play an important role.

Weak complexes of sulphur and selenium. Part II. Complex species of SO2, SOCl2, and SO2Cl2 with the thiocyanate ligand

The formation of 1 : 1 complex species between SO2, SOCl2, and SO2Cl2 with the SCN– ligand is reported in dilute solutions. Their thermodynamic constants point to a weak association of a charge-transfer type. The nature of the complex species is discussed in relation to polarisability and basicity of the SCN– ligand.

Weak complexes of sulphur and selenium. Part I. Complex species of SO2, SOCl2, and SO2Cl2 with chloride, bromide, and iodide ions

The formation of 1 : 1 complex species between SO2, SOCl2, SO2Cl2, and Cl–, Br–, and l– is reported. The stability constants of the SO2X– species were determined in acetonitrile, dimethyl sulphoxide, and water. The stability constants of SOCl2,X– and SO2Cl2,X– were determined in acetonitrile. The standard enthalpies of formation point to weak association of a charge-transfer type. The nature of association between the complexing components is discussed in relation to the acid–base characters of such components.

Weak complexes of sulphur and selenium. Part 5. Halide-ion replacement in 1:1 complexes of sulphur dioxide, thionyl chloride, and sulphonyl choride with halide ions in acetonitrile and dimethyl sulphoxide

The replacement of the iodide ligand in the complex species SO2·l-, SOCl2·l-, and SO2Cl2·l- by chloride, bromide, and thiocyanate ions has been studied spectrophotometrically. The extent of replacement depends on complex stability, the nature of the replacing ligand, and on the solvent used.

Weak complexes of sulphur and selenium. Part IV. Complex of selenium dioxide and seleninyl dichloride with halide ions

The formation of 1 : 1 complexes between SeO2 and SeOCl2 and Cl–, Br–, and I– ions is reported. The stability constants and nature of the complexes are correlated with those of SO2 and SOCl2 and the role of dimethyl sulphoxide as solvent is discussed.