Irina Karadjova - Academia.edu (original) (raw)

Papers by Irina Karadjova

Research paper thumbnail of Determination of trace elements in the Lavender inflorescence ( Lavandula angustifolia Mill.) — Lavender oil system

Microchemical Journal, 2007

Bulgaria is a famous world producer of essential oils. Quality control of the lavender oils produ... more Bulgaria is a famous world producer of essential oils. Quality control of the lavender oils produced is an important analytical task in view of their wide use in perfumery and cosmetics, the food industry and aromatherapy. The present paper studies the relationship between the trace elements content in lavender inflorescence (Lavandula angustifolia Mill.) and in lavender oil derived from this inflorescence. Three model regions were investigated: two of them are situated far from industrial areas — the village of Zelenikovo and the town of Pavel Banya, and one region is located near the Plovdiv Non-Ferrous Metallurgical Plant. The content of the elements Cd, Cr, Cu, Fe, Mn and Pb in plants was determined after acid digestion by flame and electrothermal atomic absorption spectrometry (ETAAS). Lavender oils were analyzed directly by ETAAS. The results undoubtedly show that there is no strong correlation between the trace elements content in inflorescence and in essential oils. It might be assumed that the trace elements present and accumulated in the inflorescence do not pass in lavender oil during the production by steam distillation.

Research paper thumbnail of Determination of lead in wine by hydride generation atomic fluorescence spectrometry in the presence of hexacyanoferrate(III

Analytical and Bioanalytical Chemistry, 2007

A rapid, accurate, and precise method is described for the determination of Pb in wine using cont... more A rapid, accurate, and precise method is described for the determination of Pb in wine using continuous-flow hydride generation atomic fluorescence spectrometry (CF-HGAFS). Sample pretreatment consists of ten-fold dilution of wine followed by direct plumbane generation in the presence of 0.1 mol L−1 HCl and 1% m/v K3[Fe(CN)6] with 1% m/v NaBH4 as reducing agent. An aqueous standard calibration curve is recommended for Pb quantification in wine sample. The method provides a limit of detection and a limit of quantification of 0.3 μg L−1 and 1 μg L−1, respectively. The relative standard deviation varies between 2–6% (within-run) and 4–11% (between-run) at 3–30 μg L−1 Pb levels in wine. Good agreement has been demonstrated between results obtained by CF-HGAFS and direct electrothermal atomic absorption spectrometry in analyses of red and white wines within the concentration range of 9.2–25.8 μg L−1 Pb.

Research paper thumbnail of ETAAS determination of nickel in serum and urine

Analytical and Bioanalytical Chemistry, 2002

Methods for the direct determination of Ni in human blood serum and urine by electrothermal atomi... more Methods for the direct determination of Ni in human blood serum and urine by electrothermal atomic absorption spectrometry (ETAAS) are described. Hydrogen peroxide was proposed as matrix modifier, assisting thermal decomposition of proteins during the ashing step. A pyrolysis temperature of 1,200 °C was found to be optimal while 2,100 °C and 2,200 °C were found to be optimal atomizing temperatures for Ni in serum and urine respectively. Calibration was performed by using a calibration curve prepared with aqueous standard solutions of Ni (glycine must be used as modifier for Ni in aqueous solutions). The limits of detection, defined as the blank values plus 3 times the standard deviation of the blank values, were 0.2 µg/L for both serum and urine samples. Relative standard deviations for serum samples with concentrations of Ni in the range 0.5–2 µg/L were 10–15% and for urine samples with Ni concentrations in the range 0.5–2.5 µg/L were 8–10%.

Research paper thumbnail of Determination of inorganic and methylmercury in fish by cold vapor atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

Microchemical Journal, 2008

Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish w... more Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any interspecies conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L − 1 HCl. After careful optimization of chemical parameters selective determination of Hg 2+ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl 2 as reductant and 0.1 mol L − 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg 2+ is recommended for its quantification. Both Hg 2+ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/ V NaBH 4 as reductant. Quantification of the sum of Hg 2+ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg 2+ and methylmercury (by difference between the total Hg and Hg 2+ ) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.

Research paper thumbnail of Behaviour of cadmium, cobalt and lead in chlorine-containing organic solvents in electrothermal atomic absorption spectrometry

Journal of Analytical Atomic Spectrometry, 1993

ABSTRACT

Research paper thumbnail of Trace Metal Speciation and Bioavailability in Surface Waters of the Black Sea Coastal Area Evaluated by HF-PLM and DGT

Environmental Science & Technology, 2009

Trace metal speciation in seawater from the Bulgarian Black Sea coast was studied in situ by holl... more Trace metal speciation in seawater from the Bulgarian Black Sea coast was studied in situ by hollow fiber permeation liquid membrane (HF-PLM) and by diffusion gradients in thin-film gels (DGT). The concentrations of Cd, Cu, Ni, and Pb determined by HF-PLM were lower than those measured by DGT, in agreement with their analytical windows, e.g., free metal ions provided by the HF-PLM and dynamic (mobile and labile) species by the DGT. The obtained suite of data was further used to evaluate the bioavailability of these metals to the microorganisms, which was then compared with experimental results of metal uptake to green microalga Chlorella salina. Uptake fluxes of the Cd, Cu, Ni, and Pb to C. salina, were predicted from the measured HF-PLM concentrations and laboratory experimentation in artificial seawater, in agreement with theoretical considerations. The HF-PLM and DGT appear to be promising analytical techniques for speciation and bioavailability studies in complex environmental media and allow improved understanding of the role of different chemical species in metal bioavailability (and impact) in seawaters.

Research paper thumbnail of Determination of total arsenic and toxicologically relevant arsenic species in fish by using electrothermal and hydride generation atomic absorption spectrometry

Microchemical Journal, 2006

Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish w... more Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any interspecies conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L − 1 HCl. After careful optimization of chemical parameters selective determination of Hg 2+ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl 2 as reductant and 0.1 mol L − 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg 2+ is recommended for its quantification. Both Hg 2+ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/ V NaBH 4 as reductant. Quantification of the sum of Hg 2+ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg 2+ and methylmercury (by difference between the total Hg and Hg 2+ ) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.

Research paper thumbnail of Fractionation and speciation of Cu, Zn and Fe in wine samples by atomic absorption spectrometry

Spectrochimica Acta Part B-atomic Spectroscopy, 2002

A scheme is presented for fractionation of wine components and Fe, Cu and Zn determination in dif... more A scheme is presented for fractionation of wine components and Fe, Cu and Zn determination in different fractions. The charge of the metal species was established using cation and anion exchange separation based on solid phase extraction. The resin XAD-8 was used for the separation of wine polyphenols in complexes with wine proteins and polysaccharides. Dowex ion exchange resins were used for the separation of cationic and anionic species of Fe, Cu and Zn. Flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry were used off-line for the quantitative determination of metals in the different fractions obtained. ᮊ

Research paper thumbnail of Continuous flow hydride generation-atomic fluorescence spectrometric determination and speciation of arsenic in wine

Spectrochimica Acta Part B-atomic Spectroscopy, 2005

Methods for the atomic fluorescence spectrometric (AFS) determination of total arsenic and arseni... more Methods for the atomic fluorescence spectrometric (AFS) determination of total arsenic and arsenic species in wines based on continuous flow hydride generation (HG) with atomization in miniature diffusion flame (MDF) are described. For hydride-forming arsenic, l-cysteine is used as reagent for pre-reduction and complexation of arsenite, arsenate, monomethylarsonate and dimethylarsinate. Concentrations of hydrochloric acid and tetrahydroborate are optimized in order to minimize interference by ethanol. Procedure permits determination of the sum of these four species in 5 -10-fold diluted samples with limit of detection (LOD) 0.3 and 0.6 Ag l À 1 As in white and red wines, respectively, with precision between 2% and 8% RSD at As levels within 0.5 -10 Ag l À 1 .

Research paper thumbnail of Arsenic in marine tissues — The challenging problems to electrothermal and hydride generation atomic absorption spectrometry

Spectrochimica Acta Part B-atomic Spectroscopy, 2007

All other uses, reproduction and distribution, including without limitation commercial reprints, ... more All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution's website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial A u t h o r ' s p e r s o n a l c o p y

Research paper thumbnail of Organic solvents as interferents in arsenic determination by hydride generation atomic absorption spectrometry with flame atomization

Spectrochimica Acta Part B-atomic Spectroscopy, 2006

Interference effects of various organic solvents miscible with water on arsenic determination by ... more Interference effects of various organic solvents miscible with water on arsenic determination by hydride generation atomic absorption spectrometry have been studied. Arsine was chemically generated in continuous flow hydride generation system and atomized by using a flame atomizer able to operate in two modes: miniature diffusion flame and flame-in-flame. The effects of experimental variables and atomization mode were investigated: tetrahydroborate and hydrochloric acid concentrations, argon, hydrogen and oxygen supply rates for the microflame, and the distance from the atomization region to the observation zone. The nature of the species formed in the flame due to the pyrolysis of organic solvent vapors entering the flame volume together with arsine is discussed. The observed signal depression in the presence of organic solvents has been mainly attributed to the atomization interference due to heterogeneous gas-solid reaction between the free arsenic atoms and finely dispersed carbon particles formed by carbon radicals recombination. The best tolerance to interferences was obtained by using flame-in-flame atomization (5-10 ml min − 1 of oxygen flow rate), together with higher argon and hydrogen supply rates and elevated observation heights.

Research paper thumbnail of Determination of Trace Metals in Bulgarian Lavender Oil by Electrothermal Atomic Absorption Spectrometry

Journal of Essential Oil Research, 2008

Research paper thumbnail of Preconcentration procedures for trace cadmium determination in natural aqueous systems prior to zeeman etaas

International Journal of Environmental Analytical Chemistry, 2003

Nanotrace Cd determination in natural waters using two new flotation collectors, lead(II) heptyld... more Nanotrace Cd determination in natural waters using two new flotation collectors, lead(II) heptyldithiocarbamate, Pb(HpDTC) 2 , and cobalt(III) heptyldithiocarbamate, Co(HpDTC) 3 , are presented. The optimization of the most important experimental parameters for flotation is given. Zeeman electrothermal atomic absorption spectrometry (ZETAAS) is used as an instrumental technique for Cd measurement. The results are compared with those obtained by other preconcentration procedures as independent methods. The limit of detection of ZETAAS using Pb(HpDTC) 2 as collector is 4.8 ng/L, while using Co(HpDTC) 3 it is 3.0 ng/L.

Research paper thumbnail of The biouptake and toxicity of arsenic species on the green microalga Chlorella salina in seawater

Aquatic Toxicology, 2008

The present study focuses on the biouptake, biotransformations, and toxicity of arsenic species o... more The present study focuses on the biouptake, biotransformations, and toxicity of arsenic species on the marine green alga Chlorella salina in seawater from the Bulgarian Black Sea coast. Exposure to equal concentrations of As(III) or As(V) led to equivalent levels of toxicity and total intracellular arsenic content. Biouptake and toxicity of methylated arsenic species, monomethylarsonate (MMA) and dimethylarsinate (DMA), were approximately three orders of magnitude lower than those for inorganic arsenic species. Seawater enrichment with phosphate (up to 1.3 mg P L −1 ) resulted in a significant reduction of both intracellular As content and toxicity due to As(III) and As(V). In contrast, the toxicity and intracellular content of MMA and DMA were unaffected by the presence of phosphate. We measured the distribution and excretion of intracellular arsenic species, and demonstrated that the release of As(V) and/or As(III), together with the bio-reduction of As(V) and the subsequent methylation of As(III) may be a detoxification mechanism for these algae. The implications of the results with respect to arsenic species bioavailability and toxicity in marine water are further discussed.

Research paper thumbnail of Electrothermal atomic absorption spectrometric determination of cobalt in human serum and urine

Current development of human health related studies requires a growing number of elements to be m... more Current development of human health related studies requires a growing number of elements to be monitored in biological matrices, including all essential and well-recognized toxic metals (1, 2).

Research paper thumbnail of Determination of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts by electrothermal atomic absorption spectrometry after preconcentration by column solid phase extraction

Mikrochimica Acta, 1999

Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, F... more Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts. Separation and preconcentration of trace metals is achieved by a column solid phase extraction procedure using silica gel modified with derivatives of dithiocarbamates — Na-DDTC (sodium diethyldithio-carbamate and HMDTC (ammonium hexamethylene-dithiocarbamate) as column packing material. The influence of the sorbent preparation procedure on the degree of sorption of the trace analytes is examined for different pH values of the sample solution. Isobutylmethyl ketone (IBMK) is proposed as an effective eluent for quantitative elution of retained metal ions. Optimal instrumental parameters for ETAAS determination of preconcentrated elements in organic eluate are presented. Practical application of sorbents in analysis of natural waters and alkali and alkaline earth salts is demonstrated. Proposed preconcentration procedure combined with ETAAS determination of trace analytes allows the determination of 0.04 μg l−1 Cd, 0.1 μg l−1 Cr, Cu, and Mn and 0.3 μg l−1 Co, Fe, Ni and Pb in natural waters and 1.10−7% Cd, 3.10−7% Cr and Mn, 7.10−7% Co, Ni and Pb and 2.10−6% Cu and Fe in alkali and alkaline earth salts.

Research paper thumbnail of On chromium direct ETAAS determination in serum and urine

Central European Journal of Chemistry, 2007

A simple, accurate and reliable method for direct electrothermal atomic absorption spectrometric ... more A simple, accurate and reliable method for direct electrothermal atomic absorption spectrometric (ETAAS) determination of chromium in serum and urine samples without any preliminary sample pretreatment is described. Instrumental parameters are optimized in order to define: the most suitable atomizer, optimal temperature program and efficient modifier. An appropriate quantification method is proposed taking into account a matrix interference study. Pyrocoated graphite tubes and wall atomization, pretreatment temperature of 700 °C, atomization temperature of 2600 °C, hydrogen peroxide as modifier and standard addition calibration are recommended. The accuracy of the method proposed for Cr determination in serum and urine was confirmed by comparative analysis of parallel samples after wet or dry ashing as well as by the analysis of two certified reference materials: Serum, Clin Rep 1 and Lypochek Urine, level 1. The detection and determination limits achieved for both matrices are 0.08 µg/L and 0.15 µg/L respectively. The relative standard deviation varied between 15 and 18 % for the chromium content in the samples in the range 0.08–0.2 µg/L and between 4 and 7 % for the chromium content in the range 0.2–2.0 µg/L for both matrices.

Research paper thumbnail of Electrothermal atomic absorption spectrometric determination of metallic impurities in platinum and palladium

Journal of Analytical Atomic Spectrometry, 1990

To cite this Article Kormušoska, Nataša Bakreska , Čundeva, Katarina and Stafilov, Trajče(2009) '... more To cite this Article Kormušoska, Nataša Bakreska , Čundeva, Katarina and Stafilov, Trajče(2009) 'Electrothermal atomic absorption spectrometric determination of cadmium and lead in traces in aquatic systems following flotation by two chromium(III) collectors', Journal

Research paper thumbnail of Determination of thallium in wine by electrothermal atomic absorption spectrometry after extraction preconcentration

Spectrochimica Acta Part B-atomic Spectroscopy, 2002

A simple method for extraction electrothermal atomic absorption spectroscopy (ETAAS) determinatio... more A simple method for extraction electrothermal atomic absorption spectroscopy (ETAAS) determination of Tl in wine is described. The wine sample is decomposed with a mixture of nitric acid and hydrogen peroxide and both thallium species Tl(I) and Tl(III) are extracted from 0.5 mol l KI solution into iso-butyl methyl ketone (IBMK).

Research paper thumbnail of Determination of Inorganic and Total Arsenic in Wines by Hydride Generation Atomic Absorption Spectrometry

Mikrochimica Acta, 2005

A method is described for the determination of inorganic arsenic species and total arsenic in win... more A method is described for the determination of inorganic arsenic species and total arsenic in wines by means of hydride generation atomic absorption spectrometry (HGAAS). Simple ethanol evaporation is the only pretreatment procedure proposed for wine samples prior to direct measurement of inorganic arsenic (AsIII) and As(V) species by HGAAS. The total arsenic content is determined after microwave digestion of the wine samples. The optimal parameters for the microwave digestion procedure and the next HGAAS measurement of arsenic are established. The detection limits achieved are 0.1 µg L−1 for inorganic and total arsenic determination. The relative standard deviation for both procedures and for ten independent determinations varied between 8 and 15% for arsenic species in the range of 1–30 µg L−1. The accuracy of the procedure for total arsenic determination was proved by comparative analysis using electrothermal atomic absorption spectrometry.

Research paper thumbnail of Determination of trace elements in the Lavender inflorescence ( Lavandula angustifolia Mill.) — Lavender oil system

Microchemical Journal, 2007

Bulgaria is a famous world producer of essential oils. Quality control of the lavender oils produ... more Bulgaria is a famous world producer of essential oils. Quality control of the lavender oils produced is an important analytical task in view of their wide use in perfumery and cosmetics, the food industry and aromatherapy. The present paper studies the relationship between the trace elements content in lavender inflorescence (Lavandula angustifolia Mill.) and in lavender oil derived from this inflorescence. Three model regions were investigated: two of them are situated far from industrial areas — the village of Zelenikovo and the town of Pavel Banya, and one region is located near the Plovdiv Non-Ferrous Metallurgical Plant. The content of the elements Cd, Cr, Cu, Fe, Mn and Pb in plants was determined after acid digestion by flame and electrothermal atomic absorption spectrometry (ETAAS). Lavender oils were analyzed directly by ETAAS. The results undoubtedly show that there is no strong correlation between the trace elements content in inflorescence and in essential oils. It might be assumed that the trace elements present and accumulated in the inflorescence do not pass in lavender oil during the production by steam distillation.

Research paper thumbnail of Determination of lead in wine by hydride generation atomic fluorescence spectrometry in the presence of hexacyanoferrate(III

Analytical and Bioanalytical Chemistry, 2007

A rapid, accurate, and precise method is described for the determination of Pb in wine using cont... more A rapid, accurate, and precise method is described for the determination of Pb in wine using continuous-flow hydride generation atomic fluorescence spectrometry (CF-HGAFS). Sample pretreatment consists of ten-fold dilution of wine followed by direct plumbane generation in the presence of 0.1 mol L−1 HCl and 1% m/v K3[Fe(CN)6] with 1% m/v NaBH4 as reducing agent. An aqueous standard calibration curve is recommended for Pb quantification in wine sample. The method provides a limit of detection and a limit of quantification of 0.3 μg L−1 and 1 μg L−1, respectively. The relative standard deviation varies between 2–6% (within-run) and 4–11% (between-run) at 3–30 μg L−1 Pb levels in wine. Good agreement has been demonstrated between results obtained by CF-HGAFS and direct electrothermal atomic absorption spectrometry in analyses of red and white wines within the concentration range of 9.2–25.8 μg L−1 Pb.

Research paper thumbnail of ETAAS determination of nickel in serum and urine

Analytical and Bioanalytical Chemistry, 2002

Methods for the direct determination of Ni in human blood serum and urine by electrothermal atomi... more Methods for the direct determination of Ni in human blood serum and urine by electrothermal atomic absorption spectrometry (ETAAS) are described. Hydrogen peroxide was proposed as matrix modifier, assisting thermal decomposition of proteins during the ashing step. A pyrolysis temperature of 1,200 °C was found to be optimal while 2,100 °C and 2,200 °C were found to be optimal atomizing temperatures for Ni in serum and urine respectively. Calibration was performed by using a calibration curve prepared with aqueous standard solutions of Ni (glycine must be used as modifier for Ni in aqueous solutions). The limits of detection, defined as the blank values plus 3 times the standard deviation of the blank values, were 0.2 µg/L for both serum and urine samples. Relative standard deviations for serum samples with concentrations of Ni in the range 0.5–2 µg/L were 10–15% and for urine samples with Ni concentrations in the range 0.5–2.5 µg/L were 8–10%.

Research paper thumbnail of Determination of inorganic and methylmercury in fish by cold vapor atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

Microchemical Journal, 2008

Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish w... more Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any interspecies conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L − 1 HCl. After careful optimization of chemical parameters selective determination of Hg 2+ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl 2 as reductant and 0.1 mol L − 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg 2+ is recommended for its quantification. Both Hg 2+ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/ V NaBH 4 as reductant. Quantification of the sum of Hg 2+ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg 2+ and methylmercury (by difference between the total Hg and Hg 2+ ) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.

Research paper thumbnail of Behaviour of cadmium, cobalt and lead in chlorine-containing organic solvents in electrothermal atomic absorption spectrometry

Journal of Analytical Atomic Spectrometry, 1993

ABSTRACT

Research paper thumbnail of Trace Metal Speciation and Bioavailability in Surface Waters of the Black Sea Coastal Area Evaluated by HF-PLM and DGT

Environmental Science & Technology, 2009

Trace metal speciation in seawater from the Bulgarian Black Sea coast was studied in situ by holl... more Trace metal speciation in seawater from the Bulgarian Black Sea coast was studied in situ by hollow fiber permeation liquid membrane (HF-PLM) and by diffusion gradients in thin-film gels (DGT). The concentrations of Cd, Cu, Ni, and Pb determined by HF-PLM were lower than those measured by DGT, in agreement with their analytical windows, e.g., free metal ions provided by the HF-PLM and dynamic (mobile and labile) species by the DGT. The obtained suite of data was further used to evaluate the bioavailability of these metals to the microorganisms, which was then compared with experimental results of metal uptake to green microalga Chlorella salina. Uptake fluxes of the Cd, Cu, Ni, and Pb to C. salina, were predicted from the measured HF-PLM concentrations and laboratory experimentation in artificial seawater, in agreement with theoretical considerations. The HF-PLM and DGT appear to be promising analytical techniques for speciation and bioavailability studies in complex environmental media and allow improved understanding of the role of different chemical species in metal bioavailability (and impact) in seawaters.

Research paper thumbnail of Determination of total arsenic and toxicologically relevant arsenic species in fish by using electrothermal and hydride generation atomic absorption spectrometry

Microchemical Journal, 2006

Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish w... more Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any interspecies conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L − 1 HCl. After careful optimization of chemical parameters selective determination of Hg 2+ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl 2 as reductant and 0.1 mol L − 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg 2+ is recommended for its quantification. Both Hg 2+ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/ V NaBH 4 as reductant. Quantification of the sum of Hg 2+ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg 2+ and methylmercury (by difference between the total Hg and Hg 2+ ) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.

Research paper thumbnail of Fractionation and speciation of Cu, Zn and Fe in wine samples by atomic absorption spectrometry

Spectrochimica Acta Part B-atomic Spectroscopy, 2002

A scheme is presented for fractionation of wine components and Fe, Cu and Zn determination in dif... more A scheme is presented for fractionation of wine components and Fe, Cu and Zn determination in different fractions. The charge of the metal species was established using cation and anion exchange separation based on solid phase extraction. The resin XAD-8 was used for the separation of wine polyphenols in complexes with wine proteins and polysaccharides. Dowex ion exchange resins were used for the separation of cationic and anionic species of Fe, Cu and Zn. Flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry were used off-line for the quantitative determination of metals in the different fractions obtained. ᮊ

Research paper thumbnail of Continuous flow hydride generation-atomic fluorescence spectrometric determination and speciation of arsenic in wine

Spectrochimica Acta Part B-atomic Spectroscopy, 2005

Methods for the atomic fluorescence spectrometric (AFS) determination of total arsenic and arseni... more Methods for the atomic fluorescence spectrometric (AFS) determination of total arsenic and arsenic species in wines based on continuous flow hydride generation (HG) with atomization in miniature diffusion flame (MDF) are described. For hydride-forming arsenic, l-cysteine is used as reagent for pre-reduction and complexation of arsenite, arsenate, monomethylarsonate and dimethylarsinate. Concentrations of hydrochloric acid and tetrahydroborate are optimized in order to minimize interference by ethanol. Procedure permits determination of the sum of these four species in 5 -10-fold diluted samples with limit of detection (LOD) 0.3 and 0.6 Ag l À 1 As in white and red wines, respectively, with precision between 2% and 8% RSD at As levels within 0.5 -10 Ag l À 1 .

Research paper thumbnail of Arsenic in marine tissues — The challenging problems to electrothermal and hydride generation atomic absorption spectrometry

Spectrochimica Acta Part B-atomic Spectroscopy, 2007

All other uses, reproduction and distribution, including without limitation commercial reprints, ... more All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution's website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial A u t h o r ' s p e r s o n a l c o p y

Research paper thumbnail of Organic solvents as interferents in arsenic determination by hydride generation atomic absorption spectrometry with flame atomization

Spectrochimica Acta Part B-atomic Spectroscopy, 2006

Interference effects of various organic solvents miscible with water on arsenic determination by ... more Interference effects of various organic solvents miscible with water on arsenic determination by hydride generation atomic absorption spectrometry have been studied. Arsine was chemically generated in continuous flow hydride generation system and atomized by using a flame atomizer able to operate in two modes: miniature diffusion flame and flame-in-flame. The effects of experimental variables and atomization mode were investigated: tetrahydroborate and hydrochloric acid concentrations, argon, hydrogen and oxygen supply rates for the microflame, and the distance from the atomization region to the observation zone. The nature of the species formed in the flame due to the pyrolysis of organic solvent vapors entering the flame volume together with arsine is discussed. The observed signal depression in the presence of organic solvents has been mainly attributed to the atomization interference due to heterogeneous gas-solid reaction between the free arsenic atoms and finely dispersed carbon particles formed by carbon radicals recombination. The best tolerance to interferences was obtained by using flame-in-flame atomization (5-10 ml min − 1 of oxygen flow rate), together with higher argon and hydrogen supply rates and elevated observation heights.

Research paper thumbnail of Determination of Trace Metals in Bulgarian Lavender Oil by Electrothermal Atomic Absorption Spectrometry

Journal of Essential Oil Research, 2008

Research paper thumbnail of Preconcentration procedures for trace cadmium determination in natural aqueous systems prior to zeeman etaas

International Journal of Environmental Analytical Chemistry, 2003

Nanotrace Cd determination in natural waters using two new flotation collectors, lead(II) heptyld... more Nanotrace Cd determination in natural waters using two new flotation collectors, lead(II) heptyldithiocarbamate, Pb(HpDTC) 2 , and cobalt(III) heptyldithiocarbamate, Co(HpDTC) 3 , are presented. The optimization of the most important experimental parameters for flotation is given. Zeeman electrothermal atomic absorption spectrometry (ZETAAS) is used as an instrumental technique for Cd measurement. The results are compared with those obtained by other preconcentration procedures as independent methods. The limit of detection of ZETAAS using Pb(HpDTC) 2 as collector is 4.8 ng/L, while using Co(HpDTC) 3 it is 3.0 ng/L.

Research paper thumbnail of The biouptake and toxicity of arsenic species on the green microalga Chlorella salina in seawater

Aquatic Toxicology, 2008

The present study focuses on the biouptake, biotransformations, and toxicity of arsenic species o... more The present study focuses on the biouptake, biotransformations, and toxicity of arsenic species on the marine green alga Chlorella salina in seawater from the Bulgarian Black Sea coast. Exposure to equal concentrations of As(III) or As(V) led to equivalent levels of toxicity and total intracellular arsenic content. Biouptake and toxicity of methylated arsenic species, monomethylarsonate (MMA) and dimethylarsinate (DMA), were approximately three orders of magnitude lower than those for inorganic arsenic species. Seawater enrichment with phosphate (up to 1.3 mg P L −1 ) resulted in a significant reduction of both intracellular As content and toxicity due to As(III) and As(V). In contrast, the toxicity and intracellular content of MMA and DMA were unaffected by the presence of phosphate. We measured the distribution and excretion of intracellular arsenic species, and demonstrated that the release of As(V) and/or As(III), together with the bio-reduction of As(V) and the subsequent methylation of As(III) may be a detoxification mechanism for these algae. The implications of the results with respect to arsenic species bioavailability and toxicity in marine water are further discussed.

Research paper thumbnail of Electrothermal atomic absorption spectrometric determination of cobalt in human serum and urine

Current development of human health related studies requires a growing number of elements to be m... more Current development of human health related studies requires a growing number of elements to be monitored in biological matrices, including all essential and well-recognized toxic metals (1, 2).

Research paper thumbnail of Determination of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts by electrothermal atomic absorption spectrometry after preconcentration by column solid phase extraction

Mikrochimica Acta, 1999

Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, F... more Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts. Separation and preconcentration of trace metals is achieved by a column solid phase extraction procedure using silica gel modified with derivatives of dithiocarbamates — Na-DDTC (sodium diethyldithio-carbamate and HMDTC (ammonium hexamethylene-dithiocarbamate) as column packing material. The influence of the sorbent preparation procedure on the degree of sorption of the trace analytes is examined for different pH values of the sample solution. Isobutylmethyl ketone (IBMK) is proposed as an effective eluent for quantitative elution of retained metal ions. Optimal instrumental parameters for ETAAS determination of preconcentrated elements in organic eluate are presented. Practical application of sorbents in analysis of natural waters and alkali and alkaline earth salts is demonstrated. Proposed preconcentration procedure combined with ETAAS determination of trace analytes allows the determination of 0.04 μg l−1 Cd, 0.1 μg l−1 Cr, Cu, and Mn and 0.3 μg l−1 Co, Fe, Ni and Pb in natural waters and 1.10−7% Cd, 3.10−7% Cr and Mn, 7.10−7% Co, Ni and Pb and 2.10−6% Cu and Fe in alkali and alkaline earth salts.

Research paper thumbnail of On chromium direct ETAAS determination in serum and urine

Central European Journal of Chemistry, 2007

A simple, accurate and reliable method for direct electrothermal atomic absorption spectrometric ... more A simple, accurate and reliable method for direct electrothermal atomic absorption spectrometric (ETAAS) determination of chromium in serum and urine samples without any preliminary sample pretreatment is described. Instrumental parameters are optimized in order to define: the most suitable atomizer, optimal temperature program and efficient modifier. An appropriate quantification method is proposed taking into account a matrix interference study. Pyrocoated graphite tubes and wall atomization, pretreatment temperature of 700 °C, atomization temperature of 2600 °C, hydrogen peroxide as modifier and standard addition calibration are recommended. The accuracy of the method proposed for Cr determination in serum and urine was confirmed by comparative analysis of parallel samples after wet or dry ashing as well as by the analysis of two certified reference materials: Serum, Clin Rep 1 and Lypochek Urine, level 1. The detection and determination limits achieved for both matrices are 0.08 µg/L and 0.15 µg/L respectively. The relative standard deviation varied between 15 and 18 % for the chromium content in the samples in the range 0.08–0.2 µg/L and between 4 and 7 % for the chromium content in the range 0.2–2.0 µg/L for both matrices.

Research paper thumbnail of Electrothermal atomic absorption spectrometric determination of metallic impurities in platinum and palladium

Journal of Analytical Atomic Spectrometry, 1990

To cite this Article Kormušoska, Nataša Bakreska , Čundeva, Katarina and Stafilov, Trajče(2009) '... more To cite this Article Kormušoska, Nataša Bakreska , Čundeva, Katarina and Stafilov, Trajče(2009) 'Electrothermal atomic absorption spectrometric determination of cadmium and lead in traces in aquatic systems following flotation by two chromium(III) collectors', Journal

Research paper thumbnail of Determination of thallium in wine by electrothermal atomic absorption spectrometry after extraction preconcentration

Spectrochimica Acta Part B-atomic Spectroscopy, 2002

A simple method for extraction electrothermal atomic absorption spectroscopy (ETAAS) determinatio... more A simple method for extraction electrothermal atomic absorption spectroscopy (ETAAS) determination of Tl in wine is described. The wine sample is decomposed with a mixture of nitric acid and hydrogen peroxide and both thallium species Tl(I) and Tl(III) are extracted from 0.5 mol l KI solution into iso-butyl methyl ketone (IBMK).

Research paper thumbnail of Determination of Inorganic and Total Arsenic in Wines by Hydride Generation Atomic Absorption Spectrometry

Mikrochimica Acta, 2005

A method is described for the determination of inorganic arsenic species and total arsenic in win... more A method is described for the determination of inorganic arsenic species and total arsenic in wines by means of hydride generation atomic absorption spectrometry (HGAAS). Simple ethanol evaporation is the only pretreatment procedure proposed for wine samples prior to direct measurement of inorganic arsenic (AsIII) and As(V) species by HGAAS. The total arsenic content is determined after microwave digestion of the wine samples. The optimal parameters for the microwave digestion procedure and the next HGAAS measurement of arsenic are established. The detection limits achieved are 0.1 µg L−1 for inorganic and total arsenic determination. The relative standard deviation for both procedures and for ten independent determinations varied between 8 and 15% for arsenic species in the range of 1–30 µg L−1. The accuracy of the procedure for total arsenic determination was proved by comparative analysis using electrothermal atomic absorption spectrometry.