The herbicide alachlor is one of the most widely used pesticides in the world; over 52 million pounds are applied to U.S. croplands annually. The acetanilide compounds 2-chloro-2$\sp\prime,6\sp\prime$-diethylacetanilide (CDA) and 2-hydroxy-2$\sp\prime,6\sp\prime$-diethylacetanilide (HDA) are environmental degradative products of alachlor. CDA, HDA and alachlor are ground and surface water contaminants; CDA and HDA are mutagenic in the Salmonella/microsome assay. There is a paucity of data on the environmental fate of CDA and HDA. The development of two competitive enzyme-linked immunosorbent assays (cELISA) for the detection of CDA and HDA is reported. cELISA3 is specific for CDA with a detection range of 0.015 to 10 $\mu$g/ml. Solid phase extraction of CDA residues from aqueous samples gives a 1000-fold concentration factor resulting in an effective detection limit of 15 pg/ml. cELISA4 is specific for both CDA and HDA in combination, with a detection range of 0.01 to 10 $\mu$g/ml. Solid phase extraction of aqueous samples prior to cELISA analysis results in an effective detection limit of 10 pg/ml. Chloroacetanilide herbicides and other alachlor metabolites that may be present in environmental samples do not interfere with the detection of CDA and HDA. cELISA3, cELISA4 and the antisera they are based on provide a means of studying the environmental fate of CDA and HDA through a variety of analytical strategies.

Atomic plasma emission spectroscopy provides a versatile element-specific detection tool for gas chromatography. Element selective detection has many applications in the field of petrochemical, environmental, pesticide and industrial analysis. It affords the analysis of compounds of interest in relatively complex samples, as the element selective response can flag compounds containing specific elements even if such compounds are co-eluting with other compounds. This dissertation research has been focused on the applications of GC-AED coupled with sample derivatization techniques for the analysis of complex petrochemical and industrial samples. Research centers of three different projects. Analysis of chlorofluorocarbons (CFC) was done in order to investigate the capability of the atomic emission detection system to produce compound independent elemental specific response. Atomic emission detection (GC-AED) can perform qualitative as well as quantitative analysis of unknown CFCs using only one available standard. Elemental response ratio (empirical formula) information provides the basis for qualitative analysis whereas individual elemental response forms the basis for quantitative analysis. Investigations concerning AED's compound independent element response were undertaken. It was observed that the reference standard and the sample should be similar with respect to molecular structure, elemental composition and concentration. The determination of olefins in commercial gasolines is critical as it determines the overall quality of gasoline fuel. Since gasoline samples are very complex it is difficult to get an olefin chromatographic profile using conventional single capillary gas chromatography coupled to flame ionization or mass spectroscopic detectors. However, analysis of olefins is possible by GC-AED if a hetero-atom tag is selectively introduced on the olefin molecules. The olefins were selectively and quantitatively brominated without affecting the aromatic and saturated hydrocarbon components of the gasoline. By observing the bromine emission signal by the atomic emission detector, the olefin chromatographic profile for a gasoline sample was obtained, thereby avoiding the interference from the coeluting hydrocarbons. The optimization of the bromination reaction was carried out using a known hydrocarbon mixture that typified the gasoline components. The determination of dicarboxylic acids in water samples has a very broad applicability as organic acids occur in wide variety of samples. Prior to gas chromatography the diacids were esterified by using pentafluorobenzyl bromide as an esterifying agent and tetrahexylammonium hydrogen sulfate as phase transfer catalyst. Esterfication is a single step process that yields diester molecules that contain ten fluorine atoms. By observing the fluorine emission signal from the atomic emission detector one can determine the amount of each diester. The optimization of the esterification reaction was carried out using a known diacid mixture, and unknown water samples were analyzed.

Arundo donax (Giant reed Plant) contains high level of cellulose, hemicellulose and lignin. It is used as a second generation method for the production of ethanol from lignocellulosic biomasses. Cellulose molecules comprised an unbranched polymer of 1,000 to 1,000,000 D-glucose linking units coupled with beta-1, 4 glycosidic bonds. Microorganism present in beta 1-4 gluconase breaks down the glucosidic linkage in the Microcrystalline structure of the cellulose to cellobiose molecules (a glucose dimer have a beta-1, 4 bond). The cellobiose is subsequently broken down into glucose molecules by an enzyme called beta-glucosidase. The scope of this work entails hydrolysis conversion of cellulose to glucose and other value added products using enzymatic (Cellulase)

No description available.

No description available.

Ultramicroelectrodes (UMEs) are generally defined as electrodes with sizes ≤25 µm. UMEs can be prepared by several methods including by sealing a conductive filament like thin metal wire or a single carbon fiber in a glass capillary. The small size of UMEs makes them useful as probes for measuring electroactive species in confined spaces (for example, inside living cells, etc.), and also enables very effective mass transport, resulting in rapid achievement of steady-state response and facilitating measurement of fast electrochemical reactions. Application of UMEs often requires modification of the electrode surface to improve the selectivity and the sensitivity towards the target analyte. Surface modification methods are time-consuming and may require expensive equipment. Previous research in our group demonstrated that a simple soft nitriding method could be employed to introduce surface nitrogen on carbon fiber (CF). The technique improved electrochemical response of CF-UMEs towards hydrogen peroxide (a reactive oxygen species that has been related to various malignancies and disorders) and, in separate experiments, also enabled deposition of electroactive metal nanoparticles on the UME surface. Since the presence of phosphorus heteroatoms on carbon electrodes has been shown to impart similar benefits, here we investigate a simple phosphorus doping strategy to make P-doped CF-UMEs. We compare their properties towards the electrocatalytic reduction of H2O2 to both N-doped CF-UMEs and unmodified CF-UMEs.

Elucidation of the chemical speciation of trace metals in the natural aquatic environment will lead to a better understanding of their distribution and ecological effects. One approach which can provide useful information about the chemical reactivity of metal ions is the measurement of their activity. Phase equilibrium methods are required and liquid-liquid partition equilibria are applicable. This study utilized model systems to demonstrate this applicability. The partitioning of copper(II) ions as a chelate of acetylacetone was used to determine the trace activity coefficients of the copper(II) electrolyte in the CU(N03)2-HN03-KN03, Cu(N03)2-HCl04-NaCl04 and CuC12-HCl-KCl systems over a wide range of ionic strengths (u). By careful control of pH and acetylacetone concentration only 1-3% of the metal ion was extracted. Under these conditions the amount extracted is proportional to the activity. The concentration of the bis(Acetylacetonato) Copper(II) was determined in the organic phase by spectrophotometric and atomic absorption methods but any convenient concentration technique could be used to measure the amount extracted. A comparison of activity measurements by liquid-liquid partitioning was made with electrochemical measurements by utilizing a copper ion selective electrode. The significantly lower activity coefficient values obtained by the electrochemical method were explained in terms of the liquid junction potential and the necessity for extrathermodynamic approaches to single ion activities. Potential application of the liquid-liquid partitioning method to the determination of trace activity coefficients in natural aquatic systems was demonstrated by extension of the method to measurements in copper(II) amino acid solutions at u = 0.001 and u = 0.723. The ionic strength adjustments in this case were made with NaCl. A significant difference in the free copper (II) ion activity was observed between solutions of copper(II) glycinate and copper(II) alaninate under identical conditions of metal and ligand concentrations, pH and ionic strength. The copper(II) activity measurements made in the presence of the amino acids at u = 0.723 are not possible with copper ion selective electrodes due to chloride interference.

No description available.

Sampling and sample introduction are two key steps in quantitative gas chromatography. In this thesis, a development of a previously described sampling technique as well as a novel concept for sample introduction in gas chromatography are presented. The thesis is based on two papers. Paper I describes a method for preparing physically mixed polymers for use as sorbent phases in open tubular trapping of gaseous analytes. The concept is based on mechanical disintegration and mixing of solid or liquid poly(ethylene glycol), PEG, into poly(dimethylsiloxane), PDMS, in a straightforward manner. The resulting mixture exhibits a higher affinity towards polar analytes, as compared to pure PDMS. Paper II describes a novel approach to liquid sample introduction with the split/splitless inlet, used in gas chromatography. Classical injection techniques struggle with discrimination of high boiling analytes and poor repeatability of the injected amount of analytes. The presented injection technique utilizes high voltage to obtain a spraying effect of the injected liquid. The spraying effect can be achieved with a cold needle, which is unprecedented for gas chromatographic injections. The cold needle spraying results in highly repeatable injections, free from discrimination of high boiling analytes. / QC 20101105

Ultramicroelectrodes (UMEs) have gained considerable attention over the few past decades due to the important roles they play in electrochemical studies. Electrodes with dimension less than 25 mm can generally be classified as UMEs. These electrodes exhibit enhanced electrochemical properties as their dimensions get smaller hence making nanoelectrode (production of electrodes with limiting dimensions less than 100 nm) a continuing area of interest in research. Nanometer size electrodes have advantages of high sensitivity which enables them to be used in fields such as single particle characterization and single cell analysis, and fast electron and mass transport which permits use for studying short-lived and transient electrochemical reactions such as those involved in neurochemistry. Nanoelectrodes can be fabricated via a few different strategies which include but are not limited to electrochemically etching a thin metal wire down to a cone shape or flame-etching a carbon fiber, and chemical vapor deposition of carbon in nanopipette. This work seeks to employ the use of the laser-assisted pulling method to fabricate carbon fiber electrodes sealed in glass capillary tubes. Effects of various pre- and post- treatment techniques on electrode size and stability are explored. Key words: Electrodes, Electrochemical, carbon fiber.