Ankica Antic-Jovanovic

Lowering of detection limits in flame photometry by means of modulation of the aerosol supply

Abstract An equipment with two separate nebulizers, which supply aerosol alternately with a definite and constant frequency into a flame, is described. The solution to be analyzed is sprayed by the one of the nebulizers, and the solvent is sprayed by the other. The photocurrent is amplified by an a.c. amplifier tuned to the frequency of the aerosol supply. After rectification it is measured with a d.c. meter. This way, the registered photocurrent is due only to the emission of the analyzed solution. The detection limits for some elements which were investigated with this technique are about twenty times lower than those obtained in a common manner with a steady supply under the same conditions.

The use of a novel sample modulation technique in flame spectrometry

Abstract A novel sample modulation system is described and its utility for the lowering of detection limits in flame spectrometry is shown. In the present version, the modulation is accomplished by interrupting the sample and the solvent aerosol streams emerging steadily from two separate nebulizers with a single chopper. This ensures the alternate introduction of the aerosols into the flames at a constant frequency. It has been found that the improvements obtained are of the same order of magnitude as those achieved by the technique recently described [1].

Raman spectral study of solutions of LiClO4 and Sr(ClO4)2 in some organic solvents

Abstract Raman spectra have been obtained for solutions of LiClO 4 and Sr(ClO 4 ) 2 in acetone and acetonitrile for salt concentration from 0.6 to 3M. Analysis of the solvent bands led to the identification of cation-solvent associations. An addition of NaNCS caused the replacement of the solvated molecules by NCS − ions in the inner coordination sphere of cation. Intensity measurements of the components of the ν 1 (Cue5f8N) band of SCN − yield salvation number for cations of the order 2. Component band analysis of the ν 1 (Clue5f8O) band of ClO − 4 ion gave indication for presence of solvent-separated ion pairs and contact ion pairs in the investigated solutions. The 911.5 cm −1 band of ClO − 4 is explained as 2ν 2 enhenced by Fermi resonance.

Quantitative analysis of the Raman spectra of mixtures of weakly interacting components by factor analysis methods

A system of 17 overlapped Raman spectra in the 250–350 cm–1 spectral region of the weakly interacting component mixture of 1,2-dichloroethane, dichloromethane and carbon tetrachloride has been subjected to the statistical methods of target factor analysis (TFA) and evolving factor analysis (EFA). The results have demonstrated that concentrations of substances with intense bands are successfully determined; however, there are difficulties in analyzing weak bands of one of the components, especially when applying a TFA technique. The results of such an analysis can be improved by minimal changes in one of the coordinates of a rotation vector. Comparison of these results with a synthetic spectral model suggests that problems with analysis of weak bands are caused by the presence of a strong band that greatly overlaps the weak one.

A Power Interruption Technique for Determining the Difference Between Electron and Gas Temperatures in the Argon d.c. Arc Supplied with Aqueous Aerosol

The difference between electron and gas temperatures in a low current U‐shaped d.c. arc with aqueous aerosol supply was studied using a power interruption technique. Monitoring of the temporal evolution of recombination continuum after power switch‐off revealed that it was necessary to do a correction of the measured values due to a change in electron concentration. It was shown that the plasma studied was a two temperature type and that the temperature difference ranges from 1850 K to 600 K for arc currents from 3 to 10.5 A, respectively. A comparison with literature results for pure argon arc plasma shows that aerosol introduction reduces the temperature difference.