Importance of project: A sweet hazelnut flavor, a pliant texture, and large, evenly distributed "eyes" characterize high quality Swiss of Emmenthaler cheese. The typical sweet flavor is chiefly due to bacteria which produce propionic acid, acetic acid, and carbon dioxide. The eyes are formed from the gas, mainly carbon dioxide, produced by these and other bacteria. Krett and Stine (20) have found that the lower fatty acid content of a Swiss cheese generally indicates its quality. A study of factors which may influence the amount and ratios of the volatile acids should be helpful in determining manufacturing and curing procedures which will give a fine flavored product. Purpose of investigation Commercially, Swiss cheese is usually made from raw or heat-treated milk. Experimentally, hydrogen peroxide treated milk has shown some promise. A comparison of these three milk treatments was made to determine the effect they have on the volatile fatty acid content and cheese quality. Some successful cheesemakers add no prepared cultures of propionic acid bacteria (Propionibacterium shermanii); some add small amounts, while others advocate larger inoculums. Cheese in this experiment was made with varying amounts of added Propionibacterium shermanii culture to study the relationship to the lower fatty acid content, eye formation, and quality. This experiment is a study of the butyric, propionic, and acetic acid content of 4-month old cheese as affected by the above mentioned milk treatments and Propionibacterium shermanii culture variations.

Hemoglobin, from the erythrocytes of adult and fetal pigs, was isolated and analyzed by carboxymethylcellulose column chromatography and electrophoresis on polyacetate. These techniques demonstrate the existence of four fetal components (F0, F1A, F1B, F1C) and two adult components (A0, A1) based on their elution pH values and electrophoretic mobilities. The shift from-fetal to adult forms is initiated sometime between eight weeks after birth and one year. The change is not completed until sometime after one year and the major fetal forms (F0, F1A) maintain a 15% level in a mature adult. This report is in contrast with the results of early work that indicated that pig hemoglobin was homogeneous in nature. It conforms to the work by other researchers on other animals by showing that pig hemoglobin is heterogeneous.

No description available.

This study focuses on the utilization of metal-dependent monoclonal antibodies for large-scale chromatography and addresses an aspect that has been cited to lower immunosorbent performance, namely "orientation" of antibodies on matrices. The antibodies used in this study, the "EDTAdependent" 7D7BlO and the "Ca²⁺ -dependent" HPC4 are directed against human Protein C (PC). The 7D7BI0 antibody was characterized in terms of its metaldependency and specificity. The region of PC (epitope) recognized by 7D7BlO was identified as the first 15 residues in the NH₂-terminal. Immunosorbents made with 7D7BI0 provided highly pure and functional PC. The "orientation" of the antibodies on matrices was addressed in two ways. In the first approach, performance of immunosorbents coupled through carbohydrate moieties were compared with immunosorbents coupled through peptide regions. Coupling via carbohydrate linkages, which is generally believed to be Fc-directed, did not have any advantage in terms of efficiency and recovery over coupling via peptide. / Ph. D.

Atomic emission spectroscopy is a powerful method for chemical analysis because it offers convenient qualitative and quantitative determination of the elemental composition of an analytical sample. Although most frequently used to determine the total concentration of a given analyte, atomic spectroscopy may be coupled with a separation technique to aid in the elemental identification of individual species. Recently, supercritical fluid chromatography (SFC) has gained popularity among the research community partially because SFC is much more tolerant of polar functional groups than is gas chromatorgraphy (GC). SFC can be used in applications where derivatization is not possible due to sample complexity or steric hindrance. However, these polar compounds often require the addition of polar organic solvents to SFC to improve retention characteristics and peak shape. These polar modifiers reduce or eliminate the utility of flame-based detectors. Therefore, researchers have begun to look for alternative detection systems for SFC with polar modifiers. In particular, atomic emission based detectors using plasmas have become popular to fill this void. This research stems from several characteristics that the plasma based detectors possess which make them more appealing than flame-based photometric detectors. These characteristics include improved analytical sensitivity, fewer spectral interferences, a wide dynamic range and the ability to tolerate polar organic modifiers. Possibly the most important attraction of the plasma detector is, with respect to chromatographic analyses, that this detector allows analysis of compounds that co-elute from a column because the detector is element-specific. The evaluation of the high efficiency microwave induced plasma (HEMIP) as an elemental selective detector for packed column supercritical fluid chromatography has been explored in this dissertation. The effect of CO₂ introduction on the analytical parameters of the plasma, the feasibility of coupling packed column supercritical fluid chromatography to the argon HEMIP for the determination of metals, the use of a helium sustained plasma for nonmetal determinations, and the application of the He-HEMIP as a sensitive and selective detector for packed-column SFC. / Ph. D.

An explosive vapor generator which produces transient "clouds" of explosive vapors for use in the evaluation of commercial explosive vapor detection systems has been developed based on a capillary gas chromatograph. The design of the vapor generator replaces a flame ionization detector on the gas chromatograph with an effluent heater system to provide a cloud of explosive vapor while preventing condensation onto the walls of the capillary column. This vapor source has been successfully used to produce vapors of dinitrotoluene (DNT), trinitrotoluene (TNT), and 1,3,5-trinitro-1,3,5- triazacyclohexane (RDX). The chemical composition of the output was confirmed by both ion mobility spectrometry, and quadrupole mass spectrometry. Adsorptive effects of TNT and RDX were studied in order to optimize the injection parameters, achieving detection limits three orders of magnitude lower than previously reported. The quantitative output of the system was verified using thermal tube desorption gas chromatography. / Ph. D.

The current process of selecting a column to perform a chiral separation can be characterized as more of an art than a science. This dissertation describes CHIRULE, a "chromatographic assistant" to aid in developing chiral separations. CHIRULE constructs an n-dimensional information space from a large number of known chiral separations by fragmenting the molecules at their chiral center, producing four molecular fragments. Molecular properties are calculated for each of these fragments. The properties are the axes used to place known separations into the information space. To suggest a column, the target molecule is added to the information space. Similarity property searching is used to select all known separations similar to the target molecule. The chemistry-based expert system shell CHESS used to develop CHIRULE also includes features such as functional group recognition and automated knowledge extraction techniques based on Personal Construct Theory. The results suggest that fragment property values are a route to enhanced understanding and improved selection of chiral separation methods. / Ph. D.

Size Exclusion Chromatography (SEC) is a liquid chromarographic technique used for the characterization of polymers and polymer related materials and also for the separation of small molecules. The major drawback of SEC is the lack of availability of a universal and true mass detector for providing a homogeneous response for all samples. Indirect detection methods have demonstrated to supply an alternative way to obtain a universal, sensitive and mass response in liquid chromatography. This research evaluated the indirect conductivity detection method for the size exclusion chromatographic separation of small molecules. Several studies were developed in order to understand the performance of this novel indirect detection mode. The evaluation of the initial experimental conditions snowed a dependence on the response, efficiency and elution time with the concentration of the conductivity probe added to the mobile phase. The SEC calibration curves developed for a series of standards indicated that selected conditions do not affect the separation by size. Response factors revealed a slight increase with molecular weight when they are expressed in volume or mass. Limits of detection were in the order of 20 nanoliters for small molecules. The effect of different conductivity probes on the separation and response was also studied. A modification of the original detector cell design resulted in improvement in the signal to noise ratio. / Master of Science

A study of six liquid chromatographic column packing materials was conducted. The materials investigated were: SI-60, SI-100, ALOX T, RP-2, RP-8, and RP-18 (E. M. Laboratories, Elmsford, N.Y.). The column packing materials had an average particle diameter of 10 µm and were slurry packed into stainless steel columns that were 3 mm i.d. and 250 mm in length. Two series of probe compounds were utilized to investigate the differences in selectivity exhibited by the column packing materials in the normal phase mode and in the reversed phase mode. A column oven which controlled temperature to within ± 0.2 °C over the range of 0°C to 100°C was utilized throughout the work. Four different mobile phases were used, two for the normal phase work and two for the reversed phase work. The effect of temperature was investigated in both the normal phase mode (20°C - 50°C) and in the reversed phase mode (20°C - 80°C). The results of the selectivity study indicate that the column temperature can have a pronounced effect in normal phase liquid chromatography. As temperature increased, k' values went through a minimum in some cases, indicating a change in retention mechanism. As the temperature is increased, the retention of the compounds may be increased, decreased, or remain constant. RP-2 is a versatile column packing material which is useful in both the normal phase mode and the reversed phase mode. In the normal phase mode it behaves as a low surface area adsorption column and of the three adsorbents, (SI-60, SI-100, and RP-2), it has the widest scope. In the reversed phase mode it also has the widest scope of the three reverse phase columns studied (RP-2, RP-8, and RP-18). In reversed phase liquid chromatography, increases in retention as temperature was increased were not observed and plots of log k' vs. temperature in °C resulted in straight lines with very similar slopes. Column temperature is however an important operating parameter which is useful in optimizing separations. Temperature was found to have little effect on the efficiency of the columns but was found to have a significant effect on the scope of the column packing materials in both the normal phase mode and in the reversed phase mode. When utilizing high surface area column packing materials or column packing materials with a high percentage of hydrocarbon bonded phase, temperature control is essential in order to obtain the best reproducibility. / Doctor of Philosophy

In recent years supercritical fluid chromatography has gained attention as an alternative technique to high performance liquid chromatography for the analyses of nonvolatile or thermally labile compounds, whose analysis with gas chromatography is impossible. The work presented here demonstrates a system that allows supercritical fluid extraction of the sample with subsequent direct introduction of a fraction of. this extract onto the column for analysis with supercritical fluid chromatography. Such a procedure has several inherent advantages to traditional sampling, where extraction or dissolution of the sample is done in a liquid. A valving scheme is described to accomplish this task and is evaluated for use with several different samples, including fuels and food products, with direct comparisons made between traditional sampling and direct on-line extraction. In most cases, the chromatograms were very similar, however later eluting components were sometimes lower in concentration with this method when compared to traditional sampling techniques. The apparatus was demonstrated in the analysis of high boiling coal derived material. Analysis of this material is accomplished by preliminary class separation with subsequent supercritical fluid extraction and analysis by packed column supercritical fluid chromatography. Detection included variable wavelength UV and FTIR spectrometry. The coal derived products studied were taken from a bench scale coal liquefaction reactor, in which the same catalyst was used for twenty-five consecutive days. The changes that occur as the catalyst decays were determined chromatographically for a portion of the high boiling products. The changes were noted best in the aromatic fraction analysis, where a trend towards molecules with higher numbers of condensed rings was observed as the catalyst decayed. / Master of Science