Three-phase plasma arc atomic-emission spectrometric analysis of environmental samples using an ultrasonic nebulizer

Combination of an ultrasonic nebulizer and plasma excitation sources for spectrochemical analysis offers desirable features of low detection limits, high sample throughput, wide dynamic range of operation, acceptable precision and accuracy, and simultaneous quantitative analytical capabilities. Moreover, the ultrasonic nebulizer does not require sample preconcentration. Recently we have developed a three-phase plasma arc (TPPA) for atomic emission spectrochemical analysis. In the present work, to increase the analytical utility of the three-phase plasma system, an ultrasonic nebulizer was used for sample introduction. The effects of the argon gas flow rate, current, excitation temperature have been studied. The analytical calibration curves are obtained for Ca, Cr, Fe, Mg and Mn, and detection limits have been calculated. The present technique is used to determine the concentration of the elements Ca, Cr, Fe, Mg and Mn in airborne samples.     

Test of the intercombination rules on the two excited states (0 and 1) potential parameters of the second group metal atoms perturbed by inert gases

A set of intercombination rules has been used to calculate the two excited (³0 and ³1) state potential parameters ε₁₂ and R₁₂ of Hg, Cd and Zn interacting with inert gases (Xe, Kr, Ar and Ne). The results obtained with these rules are compared with various experimental and theoretical results for these molecules. The rules can be very well used for determination of the position of the potential minimum for the two states of all molecules. Concerning the well depths of the two states (³0 and ³1) of these molecules, it is observed that for the more bounded excited state ³0 some of these rules give results that are in close agreement with experimental data especially for molecules consisting of heavy atoms but for the shallow excited state ³1 these rules cannot be used.     

Modified helium pulse-operated microwave induced plasma for spectrochemical analysis of liquid samples

To minimize problems caused by sample introduction into helium pulse operated microwave-induced plasma (He-pulsed-MIP), a simple plasma torch was developed. This torch is constructed from commonly available components with an absolute minimum of machining. In this torch, plasma is kept operating by partially isolating it from the rest of the plasma (within the plasma chamber). This auxiliary plasma is by-passed during sample or solvent injection and is therefore not affected. The design of this discharge chamber was thoroughly examined and each parameter affecting its analytical performance was evaluated. Measurements reported include effect of helium flow rate, discharge tube position and microwave power on analytical performance. Analytical calibration curves and detection limits data are shown for Ca, Cd, Cr, Cu, Fe, Mg, Ni and Zn. Plasma excitation temperature was determined using iron and copper as thermometric species. Finally, the present technique was applied to the analysis of real biological samples (liver, brain, heart, bone, kidney, tests, serum, spleen and muscles of white albino rats). The results were compared with those obtained using flame atomic absorption spectroscopy.     

Modified helium pulse-operated microwave induced plasma for spectrochemical analysis of liquid samples

To minimize problems caused by sample introduction into helium pulse operated microwave-induced plasma (He-pulsed-MIP), a simple plasma torch was developed. This torch is constructed from commonly available components with an absolute minimum of machining. In this torch, plasma is kept operating by partially isolating it from the rest of the plasma (within the plasma chamber). This auxiliary plasma is by-passed during sample or solvent injection and is therefore not affected. The design of this discharge chamber was thoroughly examined and each parameter affecting its analytical performance was evaluated. Measurements reported include effect of helium flow rate, discharge tube position and microwave power on analytical performance. Analytical calibration curves and detection limits data are shown for Ca, Cd, Cr, Cu, Fe, Mg, Ni and Zn. Plasma excitation temperature was determined using iron and copper as thermometric species. Finally, the present technique was applied to the analysis of real biological samples (liver, brain, heart, bone, kidney, tests, serum, spleen and muscles of white albino rats). The results were compared with those obtained using flame atomic absorption spectroscopy. Received: 3 February 2000 / Revised: 16 May 2000 / Accepted: 22 May 2000     

The phase shifts leading to the broadening and shift of spectral lines

The classical theory of collisional broadening and shift parameters (β, δ) of an isolated spectral line was used to obtain simple analytical formulas for calculating both β and δ. These formulas were obtained on the assumption that the short range interaction is effective only in the broadening while the long range is effective in the shift of the spectral line. These parameters β and δ depend on the limiting phase shifts responsible for broadening η_b and shift ηδ. It was found that the values of η_b and η_δ are not equal to each other as was proposed by Weisskopf η_b=η_δ=1. The maximum and average values of η_b (η_b max, η_b av) and η_δ (η_δ max, η_δ av) were obtained by numerical evaluation, using different inverse power potentials. By introducing these parameters into the approximated formulas for β and δ using Van der Waals and Lennard-Jones potential, it was found that the results of calculations for (β and δ) with different atomic transitions perturbed by different inert gases are in close agreement with earlier results. Those results, obtained earlier, were based on the Lindholm-Foley theory especially with the average values of η_b [η_b av=0.6057] and the maximum values of η_δ [η_δ max=1.57625]. The impact parameters ρ_b and ρ_δ leading to the broadening and shift of the spectral line were also obtained for different interactions. It was found that the end parameter for the broadening ρ_b is not equal to the starting parameter for the shift ρ_δ.     

Interatomic potentials for the ground state X 0 and the two excited states 1, 0 of the intercombination cadmium line 326.1 nm broadened by Kr pressure

The temperature dependence of the Cd line absorption profile at 326.1 nm perturbed by Kr has been carefully studied over a spectral range extending from 800 cm⁻¹ in the blue wing to 1200 cm⁻¹ in the red wing using a high-resolution double-beam spectrometer. The atomic densities of krypton (N_Kr) and cadmium (N_Cd) were (2.015±0.07)×10¹⁹ and (3.62±0.05)×10¹⁸ cm⁻³, respectively. The temperature dependence of the studied line profile was analyzed in the framework of the quasi-static theory. The van der Waals coefficient differences between the ground ¹0⁺ state and the two excited states ³0⁺ and ³1 (ΔC₆⁰ and ΔC₆¹) were obtained from the near red wing profile using Kuhn's law. The values of ΔC₆⁰ and ΔC₆¹ are found to be equal to 37.8±2 and 58.5±3 eV Å⁶, respectively. The ground (X ¹0⁺), and the excited (³1, ³0⁺) state potentials at the internuclear separations from 3.2 to 6.3 Å were determined. The well depths with their positions for these states are respectively equal to 134±7 cm⁻¹, 3.95±0.2 Å; 72.3±4 cm⁻¹, 4.95±0.3 Å; and 471±12 cm⁻¹, 3.6 Å. The obtained well depths with their allowable errors are in good agreement with the values obtained before for the Cd-Kr system from some theoretical results and molecular beams experiments.     

Radiological responses of different types of Egyptian Mediterranean coastal sediments

The aim of this study was to identify gamma self-absorption correction factors for different types of Egyptian Mediterranean coastal sediments. Self-absorption corrections based on direct transmission through different thicknesses of the most dominant sediment species have been tested against point sources with gamma-ray energies of ²⁴¹Am, ¹³⁷Cs and ⁶⁰Co with 2% uncertainties. Black sand samples from the Rashid branch of the Nile River quantitatively absorbed the low energy of ²⁴¹Am through a thickness of 5 cm. In decreasing order of gamma energy self-absorption of ²⁴¹Am, the samples under investigation ranked black sand, Matrouh sand, Sidi Gaber sand, shells, Salloum sand, and clay. Empirical self-absorption correction formulas were also deduced. Chemical analyses such as pH, CaCO₃, total dissolved solids, Ca²⁺, Mg²⁺, CO₃^2?, HCO₃^? and total Fe²⁺ have been carried out for the sediments. The relationships between self absorption corrections and the other chemical parameters of the sediments were also examined.     

Three-phase double-arc plasma for spectrochemical analysis of environmental samples

A new instrument, which uses a three-phase current to support a double-arc argon plasma torch for evaporation, atomization and excitation of solid or powder samples, is described. The sampling arc is ignited between the first and second electrode while the excitation arc is ignited between the second and third electrode. Aerosol generated from the sample (first electrode) is swept by argon gas, through a hole in the second electrode (carbon tubing electrode), into the excitation plasma. A tangential stream of argon gas is introduced through an inlet orifice as a coolant gas for the second electrode. This gas stream forces the excitation arc discharge to rotate reproducibly around the electrode surface. Discharge rotation increases the stability of the excitation plasma. Spectroscopic measurements are made directly in the current-carrying region of the excitation arc. An evaluation of each parameter influencing the device performance was performed. Analytical calibration curves were obtained for Fe, Al, K, and Pb. Finally, the present technique was applied for the analysis of environmental samples. The present method appears to have significant, low cost analytical utility for environmental measurements. Received: 7 July 2000 / Revised: 6 September 2000 / Accepted: 10 September 2000     

Three-phase double-arc plasma for spectrochemical analysis of environmental samples

A new instrument, which uses a three-phase current to support a double-arc argon plasma torch for evaporation, atomization and excitation of solid or powder samples, is described. The sampling arc is ignited between the first and second electrode while the excitation arc is ignited between the second and third electrode. Aerosol generated from the sample (first electrode) is swept by argon gas, through a hole in the second electrode (carbon tubing electrode), into the excitation plasma. A tangential stream of argon gas is introduced through an inlet orifice as a coolant gas for the second electrode. This gas stream forces the excitation arc discharge to rotate reproducibly around the electrode surface. Discharge rotation increases the stability of the excitation plasma. Spectroscopic measurements are made directly in the current-carrying region of the excitation arc. An evaluation of each parameter influencing the device performance was performed. Analytical calibration curves were obtained for Fe, Al, K, and Pb. Finally, the present technique was applied for the analysis of environmental samples. The present method appears to have significant, low cost analytical utility for environmental measurements.     

Experimental investigation of the line center of Hg intercombination spectral line 253.7 nm perturbed by Kr

The collision broadening and shift of the Hg intercombination spectral line 253.7 nm (6¹S₀–6³P₁) perturbed by Kr has been investigated using a high-resolution scanning Fabry–Perot interferometer. The values of the pressure broadening and shift coefficients β and δ, respectively, for the studied line have been obtained. The obtained coefficients β and δ are compared with their corresponding published experimental values and also those calculated using Lindholm–Foley impact theory.