This master's thesis deals with optimization of conditions of chemical hydride generation of tellurium and conditions of its atomization, specifically in three types of atomizers - in a diffusion flame (DF), in a heated multiple microflame quartz tube atomizer (MMQTA) and in a dielectric barrier discharge (DBD) atomizer. Tellurium hydride was generated in a flow injection arrangement and a high-resolution continuum source atomic absorption spectrometer was used for detection. As hydride generation can be only done from tetravalent species of tellurium, at first a simple procedure of pre-reduction of hexavalent species of tellurium by heating a standard in hydrochloric acid at 6 mol dm-3 was verified. Further, conditions of chemical generation were optimized with a goal to achieve as high generation efficiency as possible, namely, concentration of hydrochloric acid and sodium tetrahydroborate, volume of the reaction coil and a flow rate of carrier gas. Subsequently, conditions of atomization of tellurium hydride were examined with chosen optimal generation conditions. In the case of DF, it was an amount of hydrogen in the flame, a total flow rate of gases and observation height. In the case of MMQTA, temperature of the atomizer, a flow rate of carrier gas and a flow rate of air or oxygen needed for...

Um procedimento eletroquímico para deposição de paládio no interior de um tubo de grafite para modificação química permanente e um sistema de geração de vapor frio para a determinação de níveis traços de mercúrio em água e sedimento através de espectrometria de absorção atômica é proposto. A célula eletroquímica tubular para as deposições de paládio em fluxo foi construída aproveitando a estrutura original do tubo de grafite o qual opera como eletrodo de trabalho. Um tubo de aço inoxidável, posicionado na saída da célula, é usado como o eletrodo auxiliar. O valor do potencial aplicado no eletrodo de grafite é medido contra um micro eletrodo de referência de Ag/AgCl inserido sobre o eletrodo auxiliar. Soluções de paládio em tampão de acetato (100 milimol L-1, pH=4,70), numa vazão de 0,5 mL min-1 foram usados para executar a deposição eletroquímica durante o intervalo de tempo de 60 min. O sistema de geração de vapor frio consiste de um micro-reator de polietileno e frasco separador líquido-gás, volume total de 4,0 ml, que é descartado depois de cada amostragem para evitar inter-contaminação das amostras. Volumes de 1,0 ml de reagente (2,0% m/v NaBH4 em 0,10 mol L-1 de NaOH) e 1,0 ml de soluções analíticas ou amostras em 0,25 mol L-1 de HNO3 são levados para o reator e separador líquido-gás usando uma bomba peristáltica. O vapor de mercúrio é transportado ao tubo de grafite modificado eletroquimicamente com fluxo de argônio de 212 ml min-1 e pré-concentrado durante 120 s. O limite de detecção obtido foi 93 ng L-1 (n=20, 3δ). O desempenho deste sistema foi testado para determinação de mercúrio em água potável, água não potável e sedimentos de lagoa. A confiança de todo procedimento foi confirmada através de testes de recuperação. / An electrochemical procedure for palladium deposition on the inner of a graphite tube for permanent chemical modification and a cold vapor generation system for the determination of trace levels of mercury in water and sediment by atomic absorption spectrometry are proposed. The tubular electrochemical cell for the deposition of palladium was assembled on the original geometry of a graphite tube that operates as the working electrode. A stainless steel tube, positioned downstream from the working electrode, is used as the auxiliary electrode. The potential value applied on the graphite electrode is measured against a micro reference electrode (Ag/AgCl) inserted into the auxiliary electrode. Palladium solutions in acetate buffer (100 milimol L-1, pH=4.70), flowing at 0.5 mL min-1 for 60 min was used to perform the electrochemical deposition. A cold vapor generation system consist of a micro polyethylene reactor and gas-liquid separator flask, total volume of 4.0 mL, that is discarded after each sampling to avoid intercontamination of the samples. Volumes of 1.0 mL of reagent (2.0% m/v NaBH4 in 0.10 mol L-1 of NaOH) and 1.0 mL of reference or sample solutions in 0.25 mol L-1 of HNO3 are carried out to the reactor and gas-liquid separator by using a peristaltic pump. The mercury vapor is transported to the graphite tube electrochemically modified with argon flow (200 mL min-1) and pre-concentrated during 120 s. The detection limit obtained was 93 ng L-1 (n=20, 3δ). The performance of these system was tested for determination of mercury in potable and non-potable water and lake sediments. The reliability of the entire procedure was confirmed by recovery tests.

Um procedimento eletroquímico para deposição de paládio no interior de um tubo de grafite para modificação química permanente e um sistema de geração de vapor frio para a determinação de níveis traços de mercúrio em água e sedimento através de espectrometria de absorção atômica é proposto. A célula eletroquímica tubular para as deposições de paládio em fluxo foi construída aproveitando a estrutura original do tubo de grafite o qual opera como eletrodo de trabalho. Um tubo de aço inoxidável, posicionado na saída da célula, é usado como o eletrodo auxiliar. O valor do potencial aplicado no eletrodo de grafite é medido contra um micro eletrodo de referência de Ag/AgCl inserido sobre o eletrodo auxiliar. Soluções de paládio em tampão de acetato (100 milimol L-1, pH=4,70), numa vazão de 0,5 mL min-1 foram usados para executar a deposição eletroquímica durante o intervalo de tempo de 60 min. O sistema de geração de vapor frio consiste de um micro-reator de polietileno e frasco separador líquido-gás, volume total de 4,0 ml, que é descartado depois de cada amostragem para evitar inter-contaminação das amostras. Volumes de 1,0 ml de reagente (2,0% m/v NaBH4 em 0,10 mol L-1 de NaOH) e 1,0 ml de soluções analíticas ou amostras em 0,25 mol L-1 de HNO3 são levados para o reator e separador líquido-gás usando uma bomba peristáltica. O vapor de mercúrio é transportado ao tubo de grafite modificado eletroquimicamente com fluxo de argônio de 212 ml min-1 e pré-concentrado durante 120 s. O limite de detecção obtido foi 93 ng L-1 (n=20, 3δ). O desempenho deste sistema foi testado para determinação de mercúrio em água potável, água não potável e sedimentos de lagoa. A confiança de todo procedimento foi confirmada através de testes de recuperação. / An electrochemical procedure for palladium deposition on the inner of a graphite tube for permanent chemical modification and a cold vapor generation system for the determination of trace levels of mercury in water and sediment by atomic absorption spectrometry are proposed. The tubular electrochemical cell for the deposition of palladium was assembled on the original geometry of a graphite tube that operates as the working electrode. A stainless steel tube, positioned downstream from the working electrode, is used as the auxiliary electrode. The potential value applied on the graphite electrode is measured against a micro reference electrode (Ag/AgCl) inserted into the auxiliary electrode. Palladium solutions in acetate buffer (100 milimol L-1, pH=4.70), flowing at 0.5 mL min-1 for 60 min was used to perform the electrochemical deposition. A cold vapor generation system consist of a micro polyethylene reactor and gas-liquid separator flask, total volume of 4.0 mL, that is discarded after each sampling to avoid intercontamination of the samples. Volumes of 1.0 mL of reagent (2.0% m/v NaBH4 in 0.10 mol L-1 of NaOH) and 1.0 mL of reference or sample solutions in 0.25 mol L-1 of HNO3 are carried out to the reactor and gas-liquid separator by using a peristaltic pump. The mercury vapor is transported to the graphite tube electrochemically modified with argon flow (200 mL min-1) and pre-concentrated during 120 s. The detection limit obtained was 93 ng L-1 (n=20, 3δ). The performance of these system was tested for determination of mercury in potable and non-potable water and lake sediments. The reliability of the entire procedure was confirmed by recovery tests.

The main goal of the work presented in this thesis is to improve the reliability of existing methods for speciation analysis of organotin compounds Species-specific isotope dilution (SSID) calibration in combination with gas chromatography – inductively coupled plasma mass spectrometry was used to investigate the transformation of phenyltin species during sample preparation. Isotope-enriched phenyltin species were synthesized from corresponding isotope-enriched tin metals. SSID with a mixture of phenyltin species (PhTs) from one isotope was used to evaluate different extraction procedures for the determination of PhTs in fresh water sediment. Preparative liquid chromatography was used to produce single isotope-enriched phenyltin species making a multi-isotope spike (MI) SSID calibration possible. Different extraction procedures for the analysis of phenyltin species in biological samples were evaluated by applying MI-SSID. Degradation of TPhT and DPhT during sample extraction was observed and quantified. Accurate results were therefore obtained. A sample preparation procedure using mild extraction conditions with reasonable recoveries is described. The stability of organotin standards was investigated under different storage conditions. Mono- and diphenyltin were found to be redistributed and degraded during storage in methanol but were stabilized in sodium acetate/ acetic acid. A fast redistribution between monobutyl- and diphenyl tin has been observed and therefore it is therefore recommended that standards be derivatized as soon as possible after butyl- and phenyltin standards are mixed. Included in the thesis is also an investigation of the analytical potential of using instrumentation based on atomic absorption spectrometry (AAS) for speciation analysis of organotin compounds. The method was based on gas chromatographic separation, atomization in a quartz tube and detection by line source (LS) AAS and for comparison, by state of the art continuum source (CS) AAS. Analytical performances of CSAAS system were found to be better compared to LSAAS.

In this diploma thesis, rubidium in plant material samples was determined by atomic absoption spectrometry. Determination of plant material rubidium was performed on two different atomic absorption spectrometers (GBC 933 AA and ContrAA 700) for comparison. The selection of a proper method of atomization was essential, therefore optimizations for the flame atomizer and electrothermal atomizer were performed. On the GBC 933 AA, flame atomization was tested. The flow rate of the acetylene-air, vertical and horizontal flame profile, spectral interval width was optimized for the instrument. On the ContrAA 700, the conditions for flame atomization were optimized as well as for electrothermal atomization. The optimized parameters included the acetylene-air flow rate and the vertical flame profile again. For the electrothermal atomization, the temperature dependence of pyrolysis and the temperature dependence of atomization were optimized. Under experimentally determined optimal conditions, the determination of rubidium in fruit and vegetable juice samples was performed by the method of calibration curve. Rubidium usually accompanies toher alkali metals. In the absence of essential biogenic elements iportant for plant growth, rubidium is able to help out and take on the role of potassium.

Flame Atomic Absorption Spectrometry (FAAS) still keeps its importance despite the relatively low sensitivity / because it is a simple and economical technique for determination of metals. In recent years atom traps have been developed to increase the sensitivity of FAAS. Although the detection limit of FAAS is only at the level of mg/L, with the use of atom traps it can reach to ng/mL. Slotted quartz tube (SQT) is one of these atom traps, it is applied for determination of volatile elements / it is economical, commercially available and easy to use. In this study, a sensitive analytical method has been developed for the determination of lead with the help of SQT. Regarding the angle between the two slots of SQT, 120&deg / and 180&deg / configurations were used and the results were compared. There were three modes of SQT used. The first application was for providing longer residence time of analyte atoms in the measurement zone / 3 fold sensitivity enhancement was observed. The second mode was the usage of SQT for preconcentration of lead atoms. In the presence of a lean air-acetylene flame, analyte atoms were trapped in the inner surface of SQT for a few minutes. Then, by the help of a small volume (10-50 &amp / #956 / L) of Methyl isobutyl ketone (MIBK), analyte atoms were revolatilized and a rapid atomization took place. Using this mode, a sensitivity enhancement of 574 was obtained at a rather low (3.9 mL/min) suction rate / 1320 fold improvement was reached at higher sample suction rate (7.4 mL/min) for 5.0 min collection. The last mode involves coating of the inner surface of SQT with several kinds of transition metals. The best sensitivity enhancement, 1650 fold, was obtained by the Ta coated SQT. In addition, effects of some elements and anions on Pb signal in Tacoated-SQT-AT-FAAS were examined. Final step consists of surface analysis / chemical nature of Pb trapped on quartz and Ta surface, and the chemical nature of Ta on quartz surface were investigated by X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy.

In recent years speciation analysis is becoming more important as it is known that each chemical form of an element behaves differently in biological and environmental media. Since abundance of tellurium in earth crust is extremely low, very sensitive and accurate methods are needed to determine the concentration of tellurium. Hydride generation atomic absorption is a sensitive, fast and economical technique applied for the determination of tellurium. Speciation of tellurium can be achieved by making use of different kinetic behaviors of Te(IV) and Te(VI) upon its reaction with sodiumborohydride. A continuous flow hydride generation system was developed and parameters that affect the analytical signal were optimized. Sample solutions were prepared in 4.0 mol/L HCl / as reductant 0.5 % (w/v) sodiumborohydride in 0.5 % (w/v) NaOH was used. Quantitative reduction of Te(VI) was achieved through application of a microwave assisted prereduction of Te(VI) in 6.0 mol/L HCl solution. Sensitivity of the system was further enhanced by in-situ trapping of the formed H2Te species in a previously heated graphite furnace whose surface was modified using Pd or Ru. Overall efficiency of pyrolytic coated graphite surface was found to be 15% when hydrides are trapped for 60 seconds at 300 oC. LOD and LOQ values were calculated as 86 pg/mL and 287 pg/mL according to peak height values. Efficiency was increased by 46% and 36% when Pd and Ru modifiers were used, respectively. With Ru modified graphite tube 173 fold enhancement was obtained over 180 seconds trapping period with respect to direct ETAAS. LOD values were 6.4 and 2.2 pg/mL for Pd and Ru treated systems, respectively, for 180 s collection of 9.6 mL sample solution.

ABSTRACT DETERMINATION OF CADMIUM USING SLOTTED QUARTZ TUBE ATOM TRAP ATOMIC ABSORPTION SPECTROMETRY AND METAL COATINGS &Ouml / zcan Gurbetoglu, G. Pelin M.S., Department of Chemistry Supervisor: Prof. Dr. O. Yavuz Ataman July 2010, 76 pages Flame atomic absorption spectroscopy (FAAS) is a common technique for detecting metals and metalloids in environmental, biological and metallurgical samples. Although it is a rather old technique, it is still very reliable, simple to use and inexpensive. The technique can be used to determine the concentration of over 70 different metals in a solution. However, it has detection limits at mg/L levels. Some atom trapping methods have been developed to reach the detection limits of ng/mL levels. Slotted quartz tube (SQT) is one of these atom trapping methods. It is an important technique, since it is easy to use, applicable in all laboratories, commercially available and economical. This thesis consists of development of a sensitive method for cadmium with the help of SQT atom trap. In this study, it was used for two different purposes. One was for keeping the analyte atoms more in the light path / in other words, for increasing the residence times of analyte atoms in the measurement zone. This first application was provided a 2.9 times enhancement with respect to conventional FAAS. Second application was for trapping the analyte on the surface of the SQT, in other words, for performing on-line preconcentration of cadmium in SQT. In the presence of a lean flame, analyte samples were trapped and collected for a few minutes at a low suction rate. After finishing the collection period, analyte atoms were revolatilized with the help of a small volume of (10-50 &micro / L) methyl isobutyl ketone (MIBK) and a rapid atomization occurred. This introduction also altered the flame composition momentarily and analyte atoms were released from the surface of the SQT. Application of this method enhanced the sensitivity 2065 times with respect to conventional FAAS. Another approach to this type of atom trapping has been investigated also in this study, which was coating of SQT with some metals having low volatility. Therefore, some transition metals were coated to the surface of SQT and among them zirconium was selected as the best coating material as having the most sensitivity enhancement factor. That is why, rest of the study was performed with the Zr coated SQT. The enhancement was 3368 as compared with FAAS. Cd determination with this method provides LOD value of 8 pg/mL and Co value of 19 pg/mL. In order to see the effect of some other type of elements or ions on determination of cadmium, interference study was done.

Flame Atomic Absorption Spectroscopy (FAAS) has lover sensitivity than similar analytical methods, however it has an important place for analysis due to its easy application and economic practicability especially in metal determinations. In order to increase the sensitivity of FAAS from mg/L level to ng/L level, various atom trap systems have been used. One of these atom traps, Slotted Quartz Tube (SQT), which is easy, economical and useful for volatile element determination, is used in this study as a sensitive analytical method for determination of tellurium. In the study, determination of Te by SQT is handled in three different modules. First, only with SQT itself, longer residence time for Te atoms in the measurement zone is provided and consequently 3.2 fold sensitivity enhancement is obtained both for Te (VI) and Te (IV). In the second module, SQT is used for concentration of tellurium species in a lean flame by sending the analyte into SQT for a definite time and trapping them on the inner surface of the SQT. After trapping the analyte, in order to determine the Te concentration, a small volume (10-50 &micro / L) of organic solvent such as methyl ethyl ketone (MEK) is introduced to the flame for revolatilization and a rapid atomization of Te on the surface is provided. In this trapping method, for 5 minutes collection with a 6 mL/min suction rate, 143 fold enhancement for Te (VI) and 142 fold enhancement for Te (IV) were obtained. In the third module, different from the second one, the inner surface of the SQT is coated with different metals for increasing the amount of Te trapped on the surface and the best enhancement for tellurium is obtained with Tantalum-coated SQT with 252 fold enhancement for Te (VI) and 246 fold enhancements for Te (IV). All improvements are calculated according to the signals obtained in FAAS method. Separate calibration plots were used for Te (IV) and Te (VI).

Silver is a precious metal having antibacterial property and widely used in industry mostly for water purification and medicinal products. Therefore, the determination of trace levels of silver is important for industrial applications. Flame atomic absorption spectrometry (FAAS) is a popular technique for the determination of relatively low concentration levels. This mature technique owes its widespread application to its simplicity and low cost. However, for some occasions, FAAS technique suffers from its low sensitivity because of low nebulization efficiency and relatively short residence time of analyte atoms in the measurement zone. In order to overcome this sensitivity problem, atom traps have been developed in recent years. Slotted quartz tube (SQT) is an accessory designed to use as an atom trap in conventional flame atomic absorption burner head. This thesis study involves the development of a sensitive, simple and economical technique with the help of the SQT for the determination silver. Firstly, the technique known as SQT-FAAS was used to increase the residence time of analyte atoms in the measurement zone. In this case, limit of detection (LOD) and characteristic concentration (C0) values were found to be 19 ng/mL and 35 ng/mL, respectively. Enhancement in sensitivity with respect to FAAS was found to be 2.31 fold using SQT-FAAS. Regarding the angle between the two slots of the SQT, 180&deg / configuration was used. Secondly, in order to improve sensitivity further, the SQT was used as an atom trap (AT) where the analyte is accumulated in its inner wall prior to re-atomization. The signal is formed after reatomization of analyte atoms on the trap surface by introduction of organic solvent. For this purpose, uncoated SQT was used as a trap medium. However, there was a memory effect. Therefore, the SQT inner surface was coated with different coating elements and theoptimum conditions were found by using W-coated SQT-AT-FAAS technique. In the presence of a lean air-acetylene flame, analyte atoms were trapped in the inner surface of the SQT for 5.0 min and then revolatilized with the introduction of 25 &mu / L isobutyl methyl ketone (IBMK) / afterwards, a transient signal was obtained. These optimized parameters were used for uncoated SQT, W-coated SQT and Zr-coated SQT atom trap techniques. Sample suction rate was 6.25 mL/min in all techniques. Sensitivity was increased 54 fold using uncoated SQT-AT-FAAS technique with respect to simple FAAS technique. When W-coated SQT-AT-FAAS technique was applied, 135 fold sensitivity enhancement was obtained with respect to FAAS technique. The best sensitivity enhancement, 270 fold, was obtained using Zr-coated SQT-AT-FAAS technique. In addition, the Ag signals were more reproducible (%RSD, 1.21) when Zr was used as a coating element. After the sensitive technique was developed, interference effects of some transition and noble metals and hydride forming elements on Ag signals were investigated. Finally, surface studies were done to determine the chemical state of Ag during trapping period by using X-ray Photoelectron Spectroscopy (XPS). It was observed that the Ag analyte is retained on the SQT surface in its oxide form.