Gas phase chemiluminescence nitrogen specific detector (CLND)is used for the direct analysis of underivatized nitrogen-containing components such as alkylamines that can not be detected by the so called universal HPLC detector, the UV detector. However, alkali metal hydroxides can not be used as mobile phase constituents with the CLND because they form non volatile particulate combustion products that foul the detector. Therefore, trimethylsulfonium hydroxide (TMSOH) has been selected as a strong base for use with the CLND, because its combustion products, CO2, H2O and SxOy are volatile. An alkali-stable zirconia-based column was used and coupled to the CLND. Zirconia-based columns are mechanically and hydrolytically more stable than silica-based columns, which have a working pH range from 3 to 8 only. Zirconia-based columns can be used at a pH from 1 to 14 and can be used at temperatures up to 200˚C. The separation of amines was carried out at high pH values where the amino groups were deprotonated. Primary, secondary, tertiary and quaternary amines were separated using a pH=13.7 mobile phase that contained only TMSOH, methanol and water. Good peak shapes were observed for all, except n-alkylamines and samples that contained both amino groups and alcohol groups.

The need for sensitive and selective detectors in supercritical fluid chromatography (SFC) is particularly evident since SFC can be used to analyze classes of compounds that are not readily amenable to either gas chromatography (GC) or liquid chromatography (LC). These compounds include species that are nonvolatile or thermally labile and , in addition, contain no chromophore that can be used for spectrophoto detection. The objective of this research is therefore to interface selective chemilumninescent detectors with SFC in the sensitive detection of nitrogen- and/or sulfur containing compounds. The chemiluminecent nitrogen detector (CLND), a gas-phase detector which is specific for nitrogen-containing compounds, was first evaluated as a detector for use with capillary SFC. The potential use of the CLND for food flavor and petroleum samples was demonstrated. In addition to equimolar nitrogen response, the CLND showed good sensitivity and large linear dynamic range. Minimum detectable quantity (MDQ) was 60 pg of nitrogen with a linear range of over 3 orders of magnitude. Nitrogen to carbon selectivity of 105 was obtained. Capillary SFC with simultaneous flame ionization and chemiluminescent detection was also demonstrated. The second portion of the research investigated the CLND for packed column SFC with methanol modified CO2. The only modification made in the CLND for packed column SFC is the pyrolysis furnace. The CLND and UV were used to interface with SFC via a post-column split. Methanol-modified CO2 was also demonstrated to be compatible with the CLND even with a high mobile phase flow rate. The use of pressure and modifier programs appears to be feasible as is evidenced by the baseline studies which have been performed, as well as by the applications demonstrated. The last portion of the research focused on the evaluation of a new generation sulfur chemiluminescent detector (SCLD), which is also a gas-phase detector, with packed column SFC using both pure and methanol modified CO2. The minimum detectable quantities were determined to be 2.6 pg or 14 pg sulfur for mobile phase employing pure CO2 or 8% methanol modified CO2 respectively. The evaluation study also showed excellent selectivity and linearity, as well as day-to-day repeatability. The capabilities of the SFC-SCLD system for sulfur speciation and detection of thermally labile pesticides and polar sulfonamides, as well as petrochemical samples were presented. / Ph. D.

Ethoxyquin is an antioxidant commonly used to preserve vitamins and lipids in various food products and animal feeds. The extraction and determination of ethoxyquin is becoming increasingly important as products, which are labeled as "natural" are becoming more common. The present method of determination only ensures that ethoxyquin values are below 10-20 parts per million. Therefore, advances are needed in methods of extraction and analysis in order to lower the detection limits in various products. The first part of this research investigates the use of supercritical fluids in the extraction of ethoxyquin from lean beef and beef fat. Supercritical fluids offer the advantages of safety, time, expense, and selectivity over liquid extractions. Three fluids were examined: carbon dioxide, trifluoromethane, and 1,1,1,2-tetrafluoroethane. Carbon dioxide appeared to react with ethoxyquin during the extraction. Methanol modified hydrofluorocarbons provided more complete extractions over pure hydrofluorocarbon fluids. Methanol modified 1,1,1,2-tetrafluoroethane was used in the extraction of ethoxyquin from lean beef and beef fat, and provided a quantitative extraction at the 0.5 ppm level. The second part of this research centered on the separation and quantitation of the oxidation products of ethoxyquin through the use of high pressure liquid chromatography with chemiluminescence nitrogen detection (HPLC/CLND). When ethoxyquin is oxidized, the resulting products also exhibit antioxidative properties. While these oxidation products are known, no effort has been made to separate and quantify them in real or clean samples. HPLC/CLND allows all nitrogen containing compounds to be quantified without a known standard. This method is of extreme interest in the case of ethoxyquin oxidation products, or other types of metabolites, where standards are difficult to obtain or are unstable. HPLC/CLND allowed a separation of ethoxyquin and four of its oxidation products to be detected, thus making future studies of the antioxidant behavior of ethoxyquin feasible. / Master of Science

The objective of this research was to develop new sample preparation procedures for the isolation of sulfonamides, as well as, to determine the applicability of employing on-line nitrogen selective and mass spectrometric detection methods. The first phase of this research investigated the effect of temperature and pressure on the supercritical fluid extraction (SFE) of sulfonamides from a spiked sand matrix. Temperature effects were either positive or negative with respect to extraction rate and total recovery, depending on the pressure and extraction fluid employed. The second portion of this research compared trifluoromethane (CHF3) and carbon dioxide (CO2) as fluids for the extraction of sulfonamides from spiked non-fat dry milk, beef liver, and egg yolk were found to be more selective using CHF3 than CO2. The polar trifluoromethane improved the extraction efficiency of the polar sulfonamides from the biological matrices and also reduced the amount of co-extractives. The next phase of this research considered the effect of organic modifier and CO2 in the SFE of sulfonamides from chicken liver, beef liver and egg yolk. Methanol, ethanol, acetone, acetonitrile were compared to determine optimum conditions. A SFE method employing 20% acetonitrile modified CO2 yielded quantitative recovery of sulfonamides from chicken liver, but 20% acetone modified CO2 was required to obtain quantitative recovery from beef liver. Either 20% acetone or 20% acetonitrile yielded quantitative recovery from egg yolk. The last phase of this research focused on the evaluation of selective detection methods for sulfonamide analysis. Chemiluminescence nitrogen detection (CLND) parameters were optimized for use with packed column supercritical fluid chromatography (SFC) yielding a minimum detectable quantity (MDQ) of 5 ng of sulfamethazine, on column. Improvements in the detector design decreased the MDQ to 0.5 ng, while, decreasing the column diameter further reduced the MDQ to 125 pg. The second part of this phase evaluated PLC/Atmospheric pressure chemical ionization (APCI) mass spectrometry for the detection of sulfonamides. Sensitivity in selective ion mode was found to be as low as 50 pg on column for sulfamethazine. Supercritical fluid extracts of sulfonamides spiked at 100μg/kg in chicken liver were found to be readily detected by this method. / Ph. D.

<p>This thesis presents methods for air sampling and determination of isocyanates, amines, aminoisocyanates and anhydrides. These organic compounds are generated during thermal degradation of polymers such as polyurethane (PUR) or epoxy.</p><p>Isocyanates, amines and anhydrides are airway irritants known to cause occupational asthma. Some of the compounds are listed as human carcinogens. Many workers are exposed.</p><p>Isocyanates and anhydrides are reactive and needs to be immediately derivatized during sampling. Methods have been developed for determination of airborne isocyanates, aminoisocyanates and anhydrides using di-n-butylamine (DBA) as reagent to form stabile urea derivatives or amide derivatives. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enabled detection limits as low as 10 attomoles. A nitrogen-selective LC-detector enabled quantification of DBA-derivatives in reference solutions. </p><p>A novel sampler is presented. The sampler consists of a denuder in series with a three-stage cascade impactor and an end filter. The sampler made it possible to reveal the distribution of isocyanates between gas and different particle size fractions. During thermal degradation of PUR, isocyanates were associated to particle size fractions (<1 µm) that may penetrate to the lower airways. The distribution during 8 minutes changes noticeably. Aromatic isocyanates become associated to small particles (<1 µm). As a reference method, air-sampling was performed using an impinger filled with di-n-butylamine (DBA) in toluene, connected in series with a glass fiber filter. There was a good agreement between the denuder-impactor sampler and the reference method.</p>

This thesis presents methods for air sampling and determination of isocyanates, amines, aminoisocyanates and anhydrides. These organic compounds are generated during thermal degradation of polymers such as polyurethane (PUR) or epoxy. Isocyanates, amines and anhydrides are airway irritants known to cause occupational asthma. Some of the compounds are listed as human carcinogens. Many workers are exposed. Isocyanates and anhydrides are reactive and needs to be immediately derivatized during sampling. Methods have been developed for determination of airborne isocyanates, aminoisocyanates and anhydrides using di-n-butylamine (DBA) as reagent to form stabile urea derivatives or amide derivatives. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enabled detection limits as low as 10 attomoles. A nitrogen-selective LC-detector enabled quantification of DBA-derivatives in reference solutions. A novel sampler is presented. The sampler consists of a denuder in series with a three-stage cascade impactor and an end filter. The sampler made it possible to reveal the distribution of isocyanates between gas and different particle size fractions. During thermal degradation of PUR, isocyanates were associated to particle size fractions (&lt;1 µm) that may penetrate to the lower airways. The distribution during 8 minutes changes noticeably. Aromatic isocyanates become associated to small particles (&lt;1 µm). As a reference method, air-sampling was performed using an impinger filled with di-n-butylamine (DBA) in toluene, connected in series with a glass fiber filter. There was a good agreement between the denuder-impactor sampler and the reference method.