Reticulated vitreous carbon (RVC) is a relatively new carbon based, rigid porous material. It is produced by the pyrolysis of polyurethane foam at high temperature. It is highly conductive and well suited for use in flow stream electrochemical detectors. Working electrodes constructed from RVC with different pore sizes and geometries were used to explore their working patterns. Depending on the flow rate, two operating modes have been identified: coulometric and amperometric. Some characteristic parameters of these working electrodes have been determined or estimated from which the limiting current equation has been derived for low conversion efficiencies. The equation contains the following three categories of parameters: characteristic parameters of the porous material, geometric factors, and a hydrodynamic variable. One feature is that the limiting current is inversely proportional to the pore size to the two thirds power. The signal-to-noise ratio has been shown to be superior to that of tubular or thin layer electrodes. Porous electrodes are versatile in terms of their design, the key factor being the conversion efficiency, R. The choice of mode of operation is dictated primarily by two considerations: the nature of the application and the signal-to-noise-ratio. The comparison between the porous electrode and tubular and thin layer electrodes was made in terms of the current ratio and the ratio of the signal-to-noise-ratio. The results showed current enhancement and large signal-to-noise-ratio was obtainable using porous electrodes and this in turn suggested that a lower detect limit using porous electrodes is possible. The measurement of the hydrodynamically generated difference current using parallel flow streams was proven to be an effective approach to reject noise and, hence, to obtain low detection limits.

The purpose of the work is the design and construction of new mercury electrodes suitable for flow systems which can be used for automated electrochemical measurements. A mercury plug electrode is suggested and designed for a flow system, in which an entire electrochemical cell is assembled on-line. The surface area of the working electrode in the 0.5 mm diameter flow line was determined experimentally to be 0.00218 cm$\sp2$. Three electrochemical analytical methods were investigated. The study of Osteryoung square-wave voltammetry with the mercury plug electrode was done to see if electrode response conformed to theory. The square-wave frequency and amplitude were examined. With a low frequency (lower than 100 Hz) and a small amplitude (smaller than 50 mV), the experimental results agreed well with those obtained by theoretical calculation. Cadmium ion solutions were determined with Osteryoung square-wave voltammetry over the concentration range from 4 $\times$ 10$\sp{-7}$ to 1 $\times$ 10$\sp{-4}$ M. The results showed a linear relationship between the peak current and the concentration of cadmium when the concentration is lower than about 7 $\times$ 10$\sp{-5}$ M. A detection limit of 0.1 $\mu$M cadmium was found. In investigations using alternating current voltammetry, an ac electrochemical instrument based on digital lock-in amplifier was used. Here, the detection limit for cadmium ion was 3 nM when the number of the cycles for the multiple up/down counting was 1. Results were also obtained using larger numbers of up/down counting cycles to increase sensitivity obviously. The determination of ethanol was performed on alcoholic beverages using tensammetry. The results showed that the mercury plug electrode cell can be used not only for the determination of electroactive materials but also for the determination of the nonelectroactive materials which are surface active. The advantages of the mercury plug electrode include: (a) a small surface area (0.00218 cm$\sp2$); (b) a small cell volume (6 $\mu$L); (c) a new mercury surface for each measurement; (d) an improvement in the reproducibility of the electrode surface area; and (e) the elimination of dispersion (since the sample solution was sandwiched between two mercury plugs. In the last part of this work, a surface renewable miniature mercury pool electrode is demonstrated which improves the stability of the mercury electrode in a flowing solution and improves the reproducibility of the electrode surface area. The procedure for renewing the electrode surface is accomplished by controlling pumps. Both of the two types of new mercury electrodes are based on using flow systems to take advantage of the liquid nature of mercury.

Gas chromatography (GC) was investigated for analysis of bacterially produced poly($\beta$-hydroxyalkanoate) (PHA) and 1,3-dioxaphospholanes. Pyrolysis-gas chromatography (Py-GC) was investigated as a method of analysis for an enteral food product (Vivonex T.E.N.) and PHAs. A Redox Chemiluminescence Detector (RCD) for gas chromatography was evaluated as a selective detector. Poly($\beta$-hydroxyalkanoate) investigations included mass spectrometry (MS) and Fourier transform infrared (FTIR) in conjunction with gas chromatography (Py-GC/MS, Py-GC/IR) to provide additional information in compound characterization. Poly($\beta$-hydroxyalkanoates) investigated were poly($\beta$-hydroxybutyrate) (PHB), copolymer of $\beta$-hydroxybutyrate and $\beta$-hydroxyvalerate, P(HB-co-HV), and PHA containing functionality in the pendant group. The major pyrolyzates are unsaturated carboxylic compounds related to the monomer, dimer, trimer and tetramer units of the polymer. The pyrolyzate from the HB monomer unit is crotonic acid and for the HV unit is 2-pentenoic acid. The pyrolyzates can be chromatographed on normal non-polar column stationary phases with poor chromatographic peak shape or better peak shape can be obtained using acid deactivated stationary phases. Investigations were made into using Py-GC on whole cells as a method to monitor the polymer content without prior isolation of the polymer from the cell. The pyrolyzates were also derivatized on-line using trimethylanilinium hydroxide (TMAH) as the methylation reagent to obtain compounds which exhibit better chromatographic behavior. This reagent allows the methyl esters to be formed in the presence of heat, either from the pyrolysis or from the injection port of the gas chromatograph. This procedure allows up to tetramer units of PHB to be eluted from a non-polar column. Two bacteria strains, Alcaligenes eutrophus and Rhodobacter sphaeroides, were grown in the presence of acetate-$d\sb3$ and D$\sb2$O producing PHB containing deuterium. The PHB samples were analyzed by Py-GC/MS and FTIR to determine the level of deuteration, showing a significant level of deuterium incorporation. Synthesized 1,3-dioxaphospholane and 1,3-oxathiaphospholane compounds were separated into their stereoisomers by GC with a mid-polarity stationary phase (cyanopropylphenyl-methyl silicone). Mass spectrometry was used as the GC detector to assist in structure confirmation.

The goal of this work has been to extend the usefulness of the microwave-induced plasma (MIP) as a chromatographic detector through the development of improved instrumentation, and to illustrate the power and versatility of this technique through the development of new applications. A concentric dual flow torch (CDFT) designed for the microwave-induced plasma has been evaluated as an atomic emission detector for gas chromatography and capillary supercritical fluid chromatography. This torch configuration results in a spatially stable plasma, no silicon background, a large solvent capacity (0.5-5.0 mg carbon per second) and extended discharge tube lifetimes. Figures of merit for C, Sn, Se, Mn, B, Cl and Si are presented. Results are presented that illustrate the feasibility of using this torch as an atomic emission detector for capillary supercritical fluid chromatography. Applications have been developed using the CDFT and a commercially available AED system. Speciation of organo-tin compounds in sea water at the part per trillion level has been developed. Extracted alkyltin chlorides were converted to their hydrides inside the injection port by injecting through solid sodiumborohydride. The hydrides formed were then gas chromatographed directly followed by atomic emission detection at the 303 nm emission line of tin. Organo-manganese compounds were selectively detected in gasoline samples and reaction mixtures. Non-linear Mn response was found using the commercial AED system used while the CDFT gave linear response over two orders. Phenylmercuric acetate and phenylmercuric chloride were converted to diphenylmercury inside the injection port of a gas chromatograph by injecting the chlorides through solid sodium. tetraphenylborate. PMA was extracted from several paint samples and quantified after on-line conversion to diphenylmercury. Results compare well with atomic absorption data. A GC-AED method for the determination of isothiazolinones in the blood of premature infants has been developed. Sulfur detection at 181 nm provides high sensitivity and selectivity Injection of whole blood results in detection limits of 100 ppb active ingredients.

In the first part of the dissertation, single photon, gas phase photoionization detection in conjunction with supercritical fluid chromatography (SFC) was investigated with respect to the effects of using methanol-modified carbon dioxide mobile phases on detector performance and analytical figures of merit. The presence of relatively small amounts of methanol in the base supercritical fluid was found to result in substantial reductions in analytical sensitivity due to increased electron capture-mediated quenching of photoions and increased excitation source absorption. Reduction of ion chamber concentrations of modifier using argon make-up gas provided analytical sensitivity improvement ranging between 44 and 200%. Theories were developed to account for the increase in photoionization background signal during pressure-programmed SFC. In addition, difficulties in interfacing the photoionization detector with the SFC system were overcome due to the development of an electrolysis-based stainless steel restrictor fabrication technique. In the second part of the dissertation, coupled supercritical fluid extraction and chromatography (SFE/SFC) was used to characterize phosphite antioxidants and their degradation products in low density polyethylene (LDPE). A novel self-cryofocusing interface for coupled SFE/SFC which does not rely upon external cooling and allows the analytes to be delivered to the SFC column by direct dissolution in the supercritical mobile phase was developed and implemented for the additives characterization research; the apparatus was found to provide excellent analytical mass sensitivity using 1 milligram samples. SFE of single polyethylene pellets revealed that representative sampling was insured only by grinding multiple pellet lots. By comparing the SFE approach with that of conventional liquid-based extraction and characterization techniques such as reflux extraction followed by HPLC analysis, SFE/SFC was found to be competitive in terms of both analytical recovery and accuracy. Results indicated that both analytical reproducibility and sample processing time could be optimized by increasing the sample surface area-to-weight ratio.

Conventional inductively coupled plasma-atomic emission spectroscopy (ICP-AES) has disadvantages which can limit its usefulness in situations for which sample is restricted, materials are hazardous, or detection limits are insufficient. Large volumes of argon (10 to 15 L min$\sp{-1}$) flowing at high velocities (10 m s$\sp{-1}$) result in analyte dilution and short analyte residence times. Some of the limitations of conventional ICP-AES may be overcome by forming a non-flowing or low-flow discharge inside a quartz container. To detect metals, modifier gases such as hydrogen and hydrogen chloride must be included in the argon gas stream feeding the sealed ICP. Experimental variables for a sealed ICP system are investigated and optimized for emission spectroscopic determination of arsenic and phosphorus. Important parameters include: generator power, modifier content, discharge container geometry, operating pressure, and operating procedure. Less important are total gas flow rate, container preparation and construction, and induction coil geometry. The optimum geometry is a 40-mm sphere with an induction coil approximately 5-mm larger in diameter. A generator power of 950 W and a hydrogen content of 4% result in detection limits for arsenic and phosphorus that are in the low parts-per-billion range, comparable to those obtained with other analysis techniques. A hypothesis explaining observations of analyte emission transients is developed to provide direction for subsequent container designs. Proof of this hypothesis will require techniques to probe surface species and species distribution within the sealed ICP container. A potential application of the sealed ICP is the analysis of permanent and reactive gases. This potential is demonstrated by the quantitative and qualitative analysis of silane, a pyrophoric gas used to fabricate semiconductor devices. A six-fold excess of hydrogen chloride is required to prevent deposition of silicon oligomers. Al, As, C, Cu, Fe, Ge, Mg, Na, Sn, Ti, and Zr are detected in silane-containing mixtures. Fe, Ge, Mg, Sn, Ti, and Zr are identified in the silane. Changes in the emission spectrum when silane is added to the discharge indicate that silane alters the processes occurring in the plasma, affecting the emission of other elements.

Vibrational spectroscopy has been applied to the study of a small ring molecule, three model urethane compounds and Poly (4,4$\sp\prime$-bis(6-${\rm hydroxyhexyloxy}$)biphenyl-co-2,4-toluenediisocyanate) (2,4-TDI polyurethane) systems. The computer program, POLYGRAF, was used to estimate the stability of some conformers of the three model compounds. Grazing angle microscopy was used to study the surface structure of thin films of polyurethane. The synthesis, far infrared spectra, temperature dependent mid-infrared spectra and the Fourier transform Raman spectra are reported for polycrystalline samples of three model urethanes, 1,3-phenyl di(methyl carbamate) (1,3-PDI based urethane), 2,6-toluene di(methyl carbamate) (2,6-TDI based urethane), and 2,4-toluene di(methyl carbamate) (2,4-TDI based urethane). Geometry optimization is reported for phenyl methyl carbamate both by ab initio and molecular mechanics methods, and of the three model urethanes by molecular mechanics methods using the Dreiding I force field. The results suggest that in isotropic surroundings only a very small number of the many possible conformers of the urethane groups in these molecules contribute appreciably to the structure. In this polyurethane research, the intermolecular interaction, morphology and microstructure of 2,4-TDI polyurethane are studied. Four bands were found in the carbonyl stretching region in this polyurethane film. The bands were assigned based on temperature dependence and solution spectra. A molecular interpretation of hydrogen bonding behavior is given. The temperature dependence of infrared spectra of the 2,4-TDI polyurethane films are also reported in chapter 3 together with some kinetic data. A very thin film was prepared to study the surface behavior of 2,4-TDI polyurethane. An infrared spectrum was obtained by grazing angle reflection-absorption. The results suggest that 2,4-TDI polyurethane has a layered structure and that most of the NH groups and carbonyl groups are free on the surface. The infrared spectra of 1,4-cyclohexadiene and 1,4-cyclohexadiene-3,3,6,6-d4 were recorded in the gas phase at room temperature. From the CH stretching to the CD stretching, the frequency shift is 753 cm$\sp{-1}$. The CH$\sb2$ scissor was found at 1440 cm$\sp{-1}$ and the CD$\sb2$ scissor was found at 1071 cm$\sp{-1}$, the frequency shift is 369 cm$\sp{-1}$. From CH$\sb2$ rock to CD$\sb2$ rock, the frequency shift is 80 cm$\sp{-1}$ only.

The goal of this work was to investigate the properties of existing atomic emission systems which are useful for element-selective detection of chromatographic effluent. A microwave induced plasma (MIP) system has been optimized for the selective detection of boron in the effluent of a gas chromatograph. A method was developed for the analysis of total boron present in several lubrication oil additives and in several formulated lubrication oils. Values obtained by this method compare favorably with those obtained by other atomic emission spectroscopic (AES) methods. A direct current plasma (DCP) system has been optimized for the selective detection of boron in flowing organic liquid streams. A method was developed for the analysis of total boron present in several lubrication oil additives by flow injection analysis (FIA). A method was also developed for the qualitative separation "speciation" of these additives by size exclusion chromatography-DCP. Values obtained through this method compare favorably with values obtained through other AES methods. The MIP system was optimized for the selective detection of titanium in the effluent of the gas chromatograph. This system was used to analyze a group of reaction mixtures containing novel titanium chelates and organo-metallic compounds, as well as several organo-titanium-boron compounds. The MIP system was optimized for the selective detection of several of the group VA and group VIA elements in the effluent of the gas chromatograph. This system was used to characterize a series of coal standards (the Argonne Premium Coal Standards) by pyrolysis-GC-AES. Volatile compounds containing nitrogen, oxygen and sulfur were detected. The Py-GC-AES method was used to characterize several other coal, sedimentary and kerogen samples. Volatile phosphorous, arsenic, and selenium compounds were detected, as were compounds of nitrogen, oxygen and sulfur. The MIP system was evaluated as a detector suitable for on-line elemental analysis by simultaneous multi-element detection. Several anomalies were observed in the detector response to hydrogen, non-linear response being observed within a large set of model compounds examined. Chlorinated molecules demonstrated enhanced hydrogen response. The anomalies do not greatly affect the empirical formulae calculated for compounds, provided that the analyte mass delivered to the plasma is above $1\times10\sp{-10}$ g. Empirical formulae for a variety of model compounds, as well as for a mixture of sixteen chlorinated pesticides are presented. (Abstract shortened by UMI.)

Separation of basic compounds with maintenance of adequate peak shape has been among the most taxing of HPLC applications. Also, complete chemical class fractionation of various fuel oils has been difficult with the methods currently in use. A novel stationary phase based on newly developed surface bonding organophosphate chemistry was developed to address both of these HPLC problems using relatively simple operational procedures. The stationary phase was synthesized, characterized, and packed into a 4.6 x 250 mm HPLC column prior to conducting the HPLC investigations. Studies to investigate the peak shape of basic compounds, the separation of individual basic compounds, class fractionation using model fuel oil compounds, and class fractionation of actual fuel oil samples were conducted. The stationary phase produced chromatographic peaks of basic compounds which demonstrated minimal tailing. Chromatographic separations of various basic compounds were performed to demonstrate the increased resolution possible with a column exhibiting these characteristics. The class fractionation of fuel oils was demonstrated first using model compounds followed by the fractionation of actual fuel oil samples. Recovery studies were also performed for the fuel oil fractionation. The novel stationary phase produced exhibited characteristics which are desirable for the stated applications. Minimal tailing was produced without the use of buffers or the degradation of the column while performing chromatographic separations of basic compounds. A four class fractionation of fuel oil was produced using a linear binary gradient. Both of these results are significant advances in addressing the two stated chromatographic problems.

Many elemental analysis techniques can accurately produce and process a large volume of data in a relatively short time. However, many techniques require that the sample be in the form of a solution. The preparation to meet this requirement often involves a significant degree of time and knowledge from a chemist. Sample preparation automation can be developed to eliminate or reduce these time and knowledge requirements. A flow-through digestion device and an expert system were developed as part of an automation approach for sample preparation prior to inductively coupled plasma atomic emission spectometry (ICP-AES) analysis. The flow-through device was developed for on-line stopped-flow microwave heated digestions of organic biological material. Milk, whole blood, and urine were digested with concentrated nitric acid, concentrated sulfuric acid, and 30% hydrogen peroxide. Digestion of a sample occurs within the device when the sample and reagents are exposed to microwave energy from a commercial apparatus. The physical and chemical characteristics of the digestions dictated the device design. The expert system was designed to perform open-vessel sample digestion method development. After an initial sample digestion was attempted, and the expert system used its modification rules to develop a successful digestion procedure. The expert system then accessed a simplex program to optimize key parameters. The expert system was capable of developing accurate digestion procedures for whole milk, whole blood, and urine. Accurate results were obtained from the analysis, minimal analyte loss and contamination occurred.