Abstract Methods for tephrochronology are evaluated, in the following way: Lake sediments <500 years old from three small Antarctic lakes were analysed for identification of tephras. Subsamples were analysed for a) grain size, and identification and concentration of volcanogenic grains, b) identification of tephra horizons, c) element abundance by EPMA WDS/EDS and LA-ICP-MS, and d) possible correlations between lakes and volcanoes. Volcanogenic minerals and shards were found all through the sediment cores in all three lakes, in different abundances. A high background population of volcanogenic mineral grains, in all samples, made the identification of tephra horizons difficult, and shards could only be distinguished by certainty after chemical analysis of elements. The tephra layers commonly could not be seen by the naked eye, and, hence they are regarded as cryptotephras. Because of the small size of recent eruptions in the research area, and the travel distance of ash, most shards are small and difficult to analyse. Nine possible tephra horizons have been recorded in the three lakes, and preliminary correlations have been made. But because of analytical problems, the proposed correlations between the lakes and possible volcanic sources are preliminary.

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ABSTRACT DETERMINATION OF ARSENIC, SELENIUM AND CADMIUM IN SOME TURKISH SPICES BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY Senol, Feriye M.Sc., Department of Chemistry Supervisor: Prof. Dr. O. Yavuz Ataman July 2010, 106 Pages The major source of all the nutrient elements for human body is the daily diet which is affected by age, sex, and health status, geographic and climatic conditions. It is important to analyze food items in order to determine their elemental contents, estimate their dietary intakes and compare with recommended or tolerated intake values in order to limit or increase their consumption. Spices are taken from different parts of plants and widely used in cooking processes. They are convenient samples to investigate the distribution of elements among different parts of plants and to evaluate their daily intakes. Arsenic and selenium are both essential and toxic elements whereas cadmium is considered to be toxic to human health. The recommended dietary allowance (RDA) level of selenium ranges from 50 to 200 &mu / g/day. The RDA level of arsenic is set to be 100-200 &mu / g/day for adults to meet the requirements. The weekly tolerable intake of cadmium and arsenic are 7 and 15 &mu / g/kg, respectively whereas selenium is toxic when intake is greater than 750 &mu / g/day . In this study the analysis of a variety of Anatolian spices including daisy (Chamomillae Vulgaris), bay leaf (Folium Lauri), mint (Folium Menthane), rosehip (Rosae Caninae), sage (Folium Salviae Officinalis), thyme (Herba Thymi), cumin (Fructus Cummuni), sumac (Folium Rhois Coriariae), linden flower (Flos Tilliae) v and black pepper (Piper Nigrum) were performed and As, Cd and Se levels were determined by using inductively coupled plasma mass spectrometry (ICP-MS). The results obtained were evaluated together with the results of previous studies for determination of Na, K, Mg, Ca, Li, Zn, Fe, Cu, B, Hg, Pb and Mn by inductively coupled plasma optical emission spectrometry (ICPOES) and atomic absorption spectrometry (AAS). Samples were digested in microwave oven in optimized concentrations of HNO3 and H2O2. microwave temperature program was optimized to maximize digestion efficiency. Samples were analyzed by using direct calibration method for cadmium and standard addition method for arsenic and selenium considering the effect of HNO3 concentration on ICP-MS signals. The accuracy of the methods was checked by using Oyster Tissue 1566b SRM for cadmium and arsenic and BCR Human Hair, 397 SRM for selenium. The mean arsenic and selenium levels were found to be in the range of 100-500 &mu / g/ kg whereas cadmium levels were relatively lower falling in a range of 10-100 &mu / g/ kg with few exceptions. In order to investigate the effects of spectral and nonspectral interferences on arsenic signals interference studies were performed by using HCl, NaCl, NaNO3, CsCl, CsNO3, LiCl and LiNO3. Statistical evaluations were performed on data in order to detect on significant trends.

Knowledge about selenium content of foods containing selenium species is very important in terms of both nutrition and toxicity. Bioavailability of selenium species for human body is different from each other. Hence, speciation of selenium is more important than total selenium determination. In the selenium speciation study, chicken breast samples, selenium supplement tablets and egg samples were analyzed for their selenium contents. In chicken breast study, chickens were randomly categorized into three groups including the control group (25 chickens), inorganic selenium fed group (25 chickens) and organic selenium fed group (25 chickens). After the optimization of all the analytical parameters used throughout the study, selenomethionine, selenocystine, Se(IV) and Se(VI) were determined using Cation Exchange-HPLC-ICP-MS system. In selenium supplement tablet study, anion and cation exchange chromatographies were used to determine selenium species. Arsenic is known as toxic element, and toxicity of inorganic arsenic species, As(III) and As(V), is much higher than organic arsenic species like arsenobetaine and arsenosugars. Hence, speciation of arsenic species in any matrix related with human health is very important. In the arsenic speciation study, Cation Exchange-HPLC-ICP-MS and Cation Exchange-HPLC-ES-MS systems were used to determine arsenobetaine content of DORM-2, DORM-3 and DOLT-4 as CRMs. All of the parameters in extraction, separation and detection steps were optimized. Standard addition method was applied to samples to eliminate or minimize the matrix interference. Thiols play an important role in metabolism and cellular homeostasis. Hence, determination of thiol compounds in biological matrices has been of interest by scientists. In the thiol study, Reverse Phase-HPLC-ICP-MS and Reverse Phase-HPLC-ES-MS systems were used for the separation and detection of thiols. For the thiol determination, thiols containing &ndash / S-S- bond were reduced using dithiothreitol (DTT). Reduction efficiencies for species of interest were found to be around 100%. Reduced and free thiols were derivatized before introduction on the column by p-hydroxymercuribenzoate (PHMB) and then separated from each other by using a C8 column. In the real sample measurement, yeast samples were analyzed using HPLC-ES-MS system.

ABSTRACT ARSENIC SPECIATION IN FISH BY HPLC-ICP-MS &Ouml / ZCAN, Sefika Eroglu M.S., Department of Chemistry Supervisor: Prof. Dr. O. Yavuz ATAMAN September 2010, 103 pages Arsenic speciation in fish samples on the market was performed using isocratic elution with cation exchange column high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) detection. Total As concentrations were found by ICP-MS using samples digested by nitric acid-hydrogen peroxide solution using microwave oven digestion / the results were in the range of 1.15-12.6 &micro / g/g. Separation of organic arsenicals, namely arsenobetaine (AB), dimethylarsinic acid (DMA) and monomethylarsonic acid (MA), have been achieved in 12 minutes. Freeze-dried samples were extracted by deionized water with a shaker system / the concentrations of AB and DMA in the extract was then determined using HPLC-ICP-MS. The accuracy of the method for determining AB concentration was confirmed using certified reference material (CRM), DOLT 4 (dog fish liver) / for this CRM only preliminary data are available for AB. The arsenic compounds in 6 fish muscle samples were investigated. The predominant arsenic compound found in extracts was AB / the concentrations were in the range of 0.86-12.0 &micro / g/g. DMA concentration was 0.40&plusmn / 0.03 &micro / g/g in one of the samples / in the others it was below the limit of quantation (0.21 &micro / g/g).

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Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to determine Cr, Cu, Cd, Hg and Pb in several rice samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Ascorbic acid was used as the modifier to enhance the ion signals. The background ions at the chromium masses were reduced in intensity significantly by using 0.4 ml min-1 NH3 as reaction cell gas in the dynamic reaction cell (DRC) while a q value of 0.6 was used. Since the sensitivities of Cr, Cu, Cd, Hg and Pb in rice flour slurry and aqueous solution were quite different, standard addition and isotope dilution methods were used for the determination of Cr, Cu, Cd, Hg and Pb in these rice samples. This method has been applied to the determination of Cr, Cu, Cd, Hg and Pb in NIST SRM 1568a rice flour reference material and two rice samples purchased from the market. The analysis results of the reference material agreed with the certified values. The results for the rice samples for which no reference values were available were also found to be in good agreement between isotope dilution method and standard addition method. The method detection limits estimated from standard addition curves were about 0.44, 1.7, 0.4, 0.53 and 0.69 ng g-1 for Cr, Cu, Cd, Hg and Pb, respectively, in original rice flour.Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to the determination of Cr, Cd and Pb in several plastic samples. The influences of instrument operating conditions and slurry preparation on the ion signals were investigated. NH4NO3 was used as the modifier to enhance the ion signals. The background ions at the chromium masses were reduced in intensity significantly by using NH3 as reaction cell gas in the DRC. Standard addition method and isotope dilution method were used for the determination of Cr, Cd and Pb in these plastic samples. This method was applied to the determination of Cr, Cd and Pb in two polystyrene and a polyvinyl chloride samples. The analysis results were found to be in good agreement between isotope dilution method and standard addition method. Furthermore, we digested these samples and analyzed the digested sample solutions by ultrasonic nebulization DRC ICP-MS. The analysis results were close to the isotope dilution and standard addition results. The precision between sample replicates was better than 3% with USS-ETV-DRC-ICP-MS method. The method detection limits estimated from standard addition curves were about 6.2-9.2, 1.1-1.6 and 8.4-11 ng g-1 for Cr, Cd and Pb, respectively, in original plastic samples.

Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to the determination of As and Se in soil and sediment samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Ascorbic acid and Pd were used as the modifiers to enhance the ion signals. The background ions at the selenium masses were reduced in intensity significantly by using 1.5 ml min-1 H2 as reaction cell gas in the DRC while a q value of 0.65 was used. Since the sensitivities of As and Se in slurry solution and aqueous solution were quite different, standard addition method was used for the determination of As and Se in these samples. This method has been applied to the determination of As and Se in NIST SRM 2711 Montana soil and SRM 2709 San Joaquin soil reference materials and NRCC BCSS-1 marine sediment reference sample. The analysis results of the reference materials were agreed with the certified values. The method detection limits estimated from standard addition curves were about 0.046-0.082 and 0.019-0.024 mg g-1 for As and Se, respectively, in original soil and sediment samples.