University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Emilia Vassileva

Abbrev:
Vassileva, E.
Other Names:
Address:
Faculty of Chemistry, University of Sofia, 1 J. Bourchier av., 1126 Sofia, Bulgaria
Phone:
NA
Fax:
NA

Citations 4

"Application Of Iminodiacetate Chelating Resin Muromac A-1 In On-line Preconcentration And Inductively Coupled Plasma Optical Emission Spectroscopy Determination Of Trace Elements In Natural Waters"
Spectrochim. Acta B 2003 Volume 58, Issue 8 Pages 1541-1552
E. Vassileva and N. Furuta

Abstract: On-line system incorporating a microcolumn of Muromac A-1 resin was used for the developing of method for pre-concentration of trace elements followed by inductively coupled plasma (ICP) atomic emission spectrometry determination. A chelating type ion exchange resin has been characterized regarding the sorption and subsequent elution of 24 elements, aiming to their pre-concentration from water samples of different origins. The effect of column conditioning, pH and flow rate during the pre-concentration step, and the nature of the acid medium employed for desorption of the retained elements were investigated. A sample (pH 5) is pumped through the column at 3 mL min-1 and sequentially eluted directly to the ICP with 3 M HNO3/HCl mixtures. In order to remove residual matrix elements from the column after sample loading a short buffer wash was found to be necessary. The effectiveness of the matrix separation process was illustrated. The procedure was validated by analyzing several simple matrices, Standard River water sample as well as artificial seawater. Proposed method can be applied for simultaneous determination of In, Tl, Ti, Y, Cd, Co, Cu and Ni in seawater and for multielement trace analysis of river water. Recovery at 1 µg L-1 level for the determination of investigated 24 elements in pure water ranged from 93.1 to 96% except for Pd (82.2%) and Pb (88.1%). For the same concentration level for seawater analysis recovery was between 81.9 and 95.6% except for Hg (38.2%).

"Application Of High-surface-area ZrO2 In Preconcentration And Determination Of 18 Elements By On-line Flow Injection With Inductively Coupled Plasma Atomic Emission Spectrometry"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 1 Pages 52-59
E. Vassileva, N. Furuta

Abstract: A flow-injection analysis (FIA) system incorporating a micro-column of ZrO2 has been used for the development of an on-line multi-element method for the simultaneous pre-concentration and determination of Al, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Mo, Ni, Pb, Tl, V, Sb, Sn, and Zn by inductively coupled plasma atomic emission spectrometry (ICP-AES). The conditions for quantitative and reproducible pre-concentration, elution, and subsequent on-line ICP-AES determination were established. A sample (pH 8) is pumped through the column at 3 mL min-1 and sequentially eluted directly into the ICP-AES with 3 mol L-1 HNO3. With a sample volume of 100 mL and an elution volume of 1 mL signal enhancement 100 times better than for conventional continuous aspirating systems was obtained for the elements studied. The reproducibility (RSD %) Of the method at the 10 ng mL-1 level in the eluate is acceptable - less than 8% for five replicates. Recoveries between 95.4% and 99.9% were obtained for the elements analyzed. ZrO2, with a specific surface area of 57 m(2) g-1 and a capacity of approximately 5 mg g-1 for the elements studied, was synthesized by hydrolysis of ZrCl4. The pre-concentration system was evaluated for several simple synthetic matrices, standard water samples and synthetic seawater. The effect of foreign ions on the efficiency of pre-concentration of the elements studied was investigated. The application of a micro-column filled with high-surface-area ZrO2 and flow injection inductively coupled plasma atomic emission spectrometry enables pre-concentration and simultaneous determination of 18 elements at low concentrations (ng L-1) in different water samples.

"Use Of High Surface Area TiO2 For Preconcentration And Following Determination Of Cr Species By On-line Flow Injection Inductively Coupled Plasma Atomic Emission Spectrometry"
Analusis 2000 Volume 28, Issue 9 Pages 878-884
E. Vassileva

Abstract: A flow injection analysis (FIA) system incorporating two microcolumns of TiO2 was used for the developing of an online method for pre-concentration and sequential determination of Cr3+ and Cr6+ species by inductively coupled plasma atomic emission spectrometry (ICP-AES). The optimal conditions for both analytes have been obtained. With a sample volume of 10^-50 mL and an elution volume of 500 µL, a signal was 20-100 times higher than the signal given by a continuous aspiration system. The method gave good reproducibility with precisions less than 7 % RSD for 5 replicates at the 10 ng/ml level for both Cr-species. Recoveries between 95 and 98 % were obtained for Cr3+ and Cr6+. The pre-concentration system and the methodology proposed were validated on several natural water samples, on reference water samples as well as on synthetic seawater. It was found that the on-line detection using ICP-AES allows sequential Cr speciation analysis at the low concentration levels (ng/l) usually encountered in these media.

"Chromium Speciation Analysis By Solid-phase Extraction On A High Surface Area TiO2"
Analyst 2000 Volume 125, Issue 4 Pages 693-698
Emilia Vassileva, Konstantin Hadjiivanov, Teodor Stoychev and Christo Daiev

Abstract: The adsorption of Cr3+ and Cr6+ On different metal oxides (MgO, Al2O3, TiO2, ZrO2 and CeO2) with high specific surface areas was studied under different conditions. It was established that SiO2 can be used for selective and quantitative adsorption of Cr3+, whereas, depending on the pH, TiO2 and Al2O3 can selectively adsorb Cr3+ Or Cr6+. On the basis of the results obtained, a simple and sensitive method for the selective determination of Cr3+ and Cr6+ in natural water samples using a column solid-phase extraction on a high surface area TiO2 (anatase) was developed. The conditions for quantitative and reproducible pre-concentration, elution and subsequent ETAAS determination were established. The retention efficiency is better than 95% for Cr(3+ an)d Cr6+, giving a sensitivity enhancement of 100 for a 100 mL sample volume. The proposed method is characterized by high precision and high reproducibility. The detection limit based on the 3s criterion is 30 ng L-1 for Cr3+ and 24 ng L-1 for Cr6+.