Methods for the determination of trace elements in interfering matrices were developed. The methods involve two strategies for the reduction of interferences: the use of new pretreatment methods for use with existing instrumentation, and the development of new instrumentation. A comparison was made of inductively coupled plasma-mass spectrometry (ICP-MS) detection limits and interference reduction for arsenic by hydride generation, flow injection, continuous aspiration, and mixed gas methods. Practical considerations in implementing these common techniques, as well as in the general use and maintenance of an ELAN 5000 ICP-MS instrument are presented for the benefit of new users. Two approaches for the elimination of interferences in the determination of arsenic in gold by ICP-MS. The main challenges in this analysis were the arsenic signal suppression by gold and the polyatomic interference due to chloride. A method was developed for the batch mode reductive precipitation removal of interfering gold matrix from the sample prior to hydride generation and detection of arsenic. This method has great potential value as the basis for other simple methods for the removal of transition metals that interfere with hydride generation. An on-line anion exchange method for the removal of interfering gold prior to hydride generation was subsequently developed to improve the speed of analysis. The batch-mode reduction method for the removal of gold resulted in a better detection limit than the anion exchange method. However, the automated anion exchange gold removal method required less bench chemistry, was faster, consumed less reagents, and created less mess than the off-line method. On-line solid phase extraction methods are a valuable and increasingly popular method for the removal of matrix interferences. The automation of sample pretreatment as well as the small sample size required when the technique is combined with flow injection make it ideal for use in the analysis of hazardous materials. The severe signal suppression of uranium on lithium, beryllium, magnesium, and aluminum was overcome by the on-line flow injection-solid phase extraction removal of uranium using a column packed with Tru-Spec resin. The column was regenerated on-line using ammonium oxalate. The development of an internal combustion engine as a novel source for atomic emission spectrometry was begun. This preliminary stage of development focused on the identification of important experimental parameters to be considered in future work. A one cylinder four stroke engine was modified to allow optical access through the cylinder head. Combustion radiation was monitored with a photomultiplier tube and the signal was stored using LabView software. It is hoped that this work will be the basis for the development of an inexpensive, portable, rugged instrument that will accept a variety of fuels.

Advances in knowledge of toxicology, clinical chemistry, and nutrition have made the mere determination of an element in a sample insufficient. Both the amount of an element and the forms in which it is present need to be determined. Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful element selective detection method for elemental speciation studies, and was employed as a detection method for high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) separations. An ICP-MS ion pair HPLC method for the separation of selenoamino acid standards was developed. The method was used to identify and quantify selenoamino acids present in water extracts of selenium enriched allium and yeast samples which have been shown to have cancer preventive effects in animal or human studies. Commercially available selenium nutritional supplements were also evaluated. Selenium speciation was shown to vary with level of selenium enrichment and among samples. The method was shown to be compatible with standard ICP-MS operating conditions and electrospray ionization mass spectrometry (ESI-MS). The developed method was also shown to be applicable for sulfur and tellurium speciation studies. The oxidation and reduction of selenoamino acids was investigated by HPLC-ICP-MS. Selenoamino acids were shown to be readily oxidized, and the formation of oxidation products were monitored with time. The presence of oxidized or reduced selenoamino acids in extracts of selenium enriched samples was investigated. The reversibility of the oxidation of some selenoamino acids was demonstrated, and identification of the oxidation products was attempted by ESI-MS. A preliminary evaluation of a CE-ICP-MS interface for metalloprotein speciation was carried out using model proteins and human serum, and its effects on the separation characterized. The adsorption of lead to CE capillaries was investigated. The use of commercially coated and dynamically coated capillaries resulted in reduced lead adsorption.

Flow injection hydride generation atomic absorption spectrometry is the practice of derivatizing the analyte to the volatile hydride by flow injection and introducing it to the spectrometer in the gas phase. Although hydride generation is well developed, there are still aspects and nuances which require investigation to improve the understanding of this method of sample introduction. The suggestion that the addition of various surfactants to the reagents in the hydride forming reaction has beneficial effects has been investigated. Although, in previous reports, an increase in sensitivity had been reported in the presence of surfactants, such an improvement was not observed for the flow injection procedure used in the work described in this dissertation. The effect of dissolved salts on the hydride forming reaction has been investigated. An increase in sensitivity in the presence of high concentrations of dissolved salts has been observed. This has been attributed to an increase in the proportion of the volatile hydride which is removed from the reagents in the on-line procedure. In the hydride trapping procedure, the hydrides are trapped on the interior of an electrothermal atomizer prior to atomization. Although previous reports have indicated that one may improve the limit of detection simply by increasing sample size, a practical and theoretical investigation concluded that the relationship is not linear, and that the limit of detection is limited by impurities in the reagents. Methods for the determination of lead by hydride generation with quartz tube and electrothermal atomization have been developed. The use of an oxidizing agent makes this method a little more complicated than for other elements. The determination of total selenium in urine has been attempted using an on-line digestion procedure in which bromine is generated in-situ. Whilst this method has been demonstrated to be effective in an off-line procedure, the development of a method with on-line digestion was not successful. The use of an alternative oxidizing agent and energy supply mechanism would be appear to be necessary.

The area of atomic spectrometry has long suffered from inefficient sample preparation and introduction systems. Microwave heating can be a powerful technique for improving these systems but has tending not to be well understood and used in analytical chemistry. The purpose of this work has been to use microwave energy in order to improve sample preparation and introduction for plasma source spectrometry. An objective of this work has been to develop an on-line pressurized microwave digestion system. This system was developed to be capable of digesting difficulty soluble organic materials with nitric acid alone rapidly while reducing possibilities for contamination and providing the possibility for automation. The use of microwave energy has been considered as a technique for desolvating an aqueous aerosol prior to solvent removal using a Nafion dryer. The purpose of this system was to increase the efficiency of sample introduction to a plasma source mass spectrometer. In order to accomplish this some fundamental studies of microwave interaction with water droplets were performed and a theoretical background was developed.

Methods for determination and speciation of inorganic and organic selenium in complex matrices involving, inductively-coupled plasma mass spectrometry (ICP-MS), inductively-coupled plasma atomic emission spectrometry (ICP-AES) and high performance liquid chromatography (HPLC) were developed. Selenium species were separated and detected by mixed-mode weak anion exchange and reversed-phase stationary phases with ICP-MS and ICP-AES detection. Selenium-containing nutritional supplements, wheat flour and selenized yeast, were analyzed and the major selenium species were identified and quantified by HPLC-ICP-MS equipped with a dynamic reaction cell (DRC). The quantification response factors for different selenium and sulfur compounds, analyzed by DRC-ICP-MS and ICP-AES were determined. Possible reasons for the obtained results were discussed. The effects of arsenic and selenium added simultaneously to the growth media of Helianthus annus (sunflowers), red sunflowers and Eichhornia crassipes (water hyacinths) were determined with respect to accumulation and metabolism. Total selenium and arsenic in shoots and roots was determined. Quantification of the selenium and arsenic species in E. crassipes by HPLC-ICP-MS and HPLC-ICP-AES was also performed. An accurate and reliable method was developed for the determination of functionalized gold nanoparticles in hepatocarcinoma cell tissues and rat brain material by ICP-MS. A comparison between the gold accumulated in cell and brain tissues treated with neutral, positive and negative functionalized gold nanoparticles was performed.

Speciation of selenium is of interest because selenium is both essential and toxic to humans, depending on the species and amount ingested. Following the discovery in the Clark study that selenium supplementation (in the form of selenized yeast) could reduce the incidence of some types of cancer, selenium-enriched yeast and other materials have been commercialized or proposed as supplements. However, regulation with respect to quality, storage conditions, stability and content of selenium supplements is a problem. The speciation and stability of organoselenium compounds in yeast-based and yeast-free selenium supplement samples have been studied. Enzymatic extraction enabled selenium speciation profiles to be obtained by ion-pair reversed phase high performance liquid chromatography with inductively-coupled plasma mass spectrometry (HPLC-ICP-MS) and gas chromatography with atomic emission detection (GC-AED). Prior to the GC analyses, the extracts were derivatized with ethylchloroformate. Coated fiber solid-phase microextraction (SPME) was used to extract volatile selenium species for determination by GC-AED and GC-mass spectrometry (GC-MS). Total selenium concentrations were obtained by ICP-MS and ICP-optical emission spectroscopy (ICP-OES). Close similarities of speciation were observed between extended storage and brief heating at elevated temperatures of yeast-based selenium supplements. In both cases selenomethionine, the major component in these supplements, was observed to degrade to form S-(methylseleno)cysteine, a sulfur-selenium amino acid, and selenomethionine selenoxide. Selenium concentrations in saliva were determined by electrothermal atomic absorption spectrometry (ET-AAS) and flow injection-atomic absorption spectrometry with hydride generation (FI-HG-AAS). Selenium concentrations were comparable in both methods.

Group III Metal alkyl compounds, such as trimethylindium (TMI), trimethylaluminum (TMA), and trimethylgallium (TMG) are used in metal organic chemical vapor deposition (MOCVD) process to grow semiconductor layers. The analysis of these metal alkyls that are used for growing semiconductor layers is important to ensure product quality. In addition to determining the impurity concentration, its speciation is equally important. This is because volatile impurities are more harmful to the product than the non-volatile ones because they get easily incorporated in the final product. Attempts were made to analyze the samples by inductively coupled plasma-atomic emission spectrometry (ICP-AES) by dissolving them in xylene and kerosene. Different types of calibrations were performed and it was determined that a positive bias exists if non-volatile standards are used for quantification of analytes. This bias is mainly because the impurity analytes are volatile in nature hence more sensitive in nature. A chemometric scheme was developed to remove this calibration bias by analyzing samples at two different spray chamber temperatures. This scheme results in data that are consistent with decomposition experiments where the sample was converted to inorganic form prior to analysis. As verification experiments, exponential dilution results were obtained and they agree with decomposition and chemometric schemes. A graphite furnace was used for the quantification of volatile analytes. Chemical modifiers (ethers with heavy alkyl groups) were used to achieve a temporal separation between the matrix and the analyte. This solved the matrix suppression effect on analytes due to simultaneous vaporization of the matrix and analyte. The concentrations of analytes from different techniques were found to be consistent with each other.

The development of methods for the determination of cadmium and lead at the ultra-trace concentration level has been the object of great attention during the past 20 years. The reason for this interest is their high toxicity even at these low levels, given the fact that once exposure has occurred the elements are accumulated in the body. Several instrumental techniques have been applied to the determination of cadmium and lead in biological and environmental samples, such as urine, blood, hair, foodstuffs, natural and domestic waters, etc. The variation in the complexity of these matrices is quite large, so that measuring the contents of cadmium and lead is a difficult operation because of the concentration of interfering species coexisting in the samples with a low concentration of the analytes. The application of chemical vapor generation procedures to this task offers the possibility to transfer the analyte to a medium free of interferences in a concentration that facilitates a determination by means of spectrometric techniques. In the work described in this dissertation, flow injection methods for the determination of cadmium and lead were devised according to two approaches: the generation of the vapor species with simultaneous transport and detection in an atomization T-cell placed above the burner of a Perkin Elmer 3100 atomic absorption spectrometer; and the generation of the vapor species for their preconcentration on the iridium-coated interior surface of a graphite furnace atomizer, whose temperature was thereafter raised for atomization and detection in two electrothermal atomic absorption spectrometers: a Perkin Elmer 4100ZL, and a Perkin Elmer SIMAA6000. For both approaches, the limits of detection obtained were in the low ng l–1 range. Special attention was given to: (a) the testing of several different designs of gas-liquid separators to maximize the efficiency in the transfer of the analytes from the sample to the atomizer while minimizing transfer of liquid, (b) corroborate the enhanced efficiency reported for several additives such as surfactants and transition metals, and (c) improve the limits of detection in the determination of lead by minimizing contamination of the analytical blank.

Two versions of an enclosed inductively coupled plasma source for atomic emission spectrometry have been developed for the direct analysis of specialty gases: a low-flow enclosed ICP (EICP) discharge sustained inside a spherical quartz container, and an extended, closed-torch ICP (ECT-ICP) based on a conventional ICP torch. The former is optimized for halogens and hydrogen halogenides, and the latter is designed for volatile inorganic hydrides, phosphine in particular. Both techniques offer rapid multielement analysis, wide linear dynamic range, direct sample introduction, minimal sample consumption, and instant atomization of both particulate and gaseous impurities. All parts of the arrangements on are leak-proof and corrosion resistant to ensure safe handling of toxic, corrosive, or otherwise reactive samples and to minimize sample contamination. Four complementary calibration approaches have been studied: gas standard dilution, vapor phase introduction, and exponential dilution, Arsine, silane, and hydrogen sulfide diluted with argon were used as gas standards for As, Si, and S calibration. Volatile compounds (e.g., trimethylaluminum, carbon tetrachloride, iron pentacarbonyl, diethylzinc, trimethylchlorosilane, triethylgermanium chloride, tetramethyltin, tetraethyllead) were introduced into an exponential dilution flask flushed with argon for Al, C, Fe, Pb, Si, Sn, and Zn calibration. Different organometallic compounds can be employed in the exponential dilution technique; however, some of them partially decompose or adsorb to the surfaces before reaching the EICP discharge owing to their reactivity. Indirect semiquantitative calibration based on the ratios of spectral line intensities measured in the EICP and a conventional ICP has been evaluated. The electron and excitation temperatures in both sources were determined and maintained in a certain fashion, so that atomic line intensities in both were correlated. Three chlorine samples were analyzed using an EICP discharge in 100% chlorine. Detection limits ranged from low ppb (Al, As, Fe, Ge, Pb, Sn, Si, Zn) to sub-ppm (C, S) levels. Phosphine samples were diluted 10-fold with argon for the analysis by ECT-ICP, and the detection limits in phosphine were approximately 10 times higher than in chlorine. Hydrogen bromide was analyzed qualitatively.

Speciation has become an important area of research in the fields of food and environmental analysis because the nutritional value and toxicity of an element depend on its chemical form. For that purpose a Gas Chromatography separation device was used coupled with Atomic Emission Detector (GC-AED) that provided detection for the specific element of interest even though when it may be present in very small amounts or co-elute with other components. The effect of hydrogen and oxygen reagent gases on selenium and sulfur detection using the GC-AED was studied, as well as the helium make-up flow gas. The figures of merit for both selenium and sulfur were studied. In theory, the GC-AED response should be independent of the structure of the compound that is analyzed and only depend on the number of atoms of the element on the plasma. The objective was to determine if the AED response was compound independent for Se and S. In the cases where compound independent calibration behaviour was observed, empirical formula determination was made for that element. In order to study amino acids by GC, they need to be derivatized first in order to make them volatile enough for GC. The derivatization procedure chosen was ethylation by ethylchlroformate because is a simple procedure that derivatizes both amino and carboxylic group in one step. The derivatization parameters, such as amount of reactant, best solvent, reproducibility, extraction yield and effect of interferences were studied. Enriched selenium samples, such as yeast, garlic, bacteria, seeds, and nutritional supplements, were studied. The selenium profile in those samples was compared depending on the sample and the total amount of selenium present. The selenium profile was also compared with the sulfur profile for those samples. Also, different extraction procedures were tried, such as hot water, TMAH, and enzymatic extraction. The percentage of selenium as selenomethionine in the samples was calculated either by external calibration or standard addition. Geochemical samples were also analyzed using the GC-AED and selenium-containing compounds were identified in those samples.