Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 179-201).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 100-108).

This thesis describes the evaluation and application of the atomic emission detector as a detector for capillary gas chromatography. Chapter 1 is a general introduction to the technique, describing the development of the atomic emission detector, the theory of its operation, and some of its applications. This chapter also includes a detailed description of chromatography theory. Chapter 2 describes the experimental conditions used throughout the course of this work. Chapter 3 concentrates on compound independent calibration, beginning with a general introduction to the area and a discussion of studies already made. Four groups of compounds were used to determine the ability of the atomic emission detector to perform compound independent calibration. Initial studies with a group of similar hydrocarbons showed little or no compound/structure dependence. However, results from the same study with a group of phenols did indicate some structure dependence for carbon and oxygen, but when chloroanisoles were tested, this compound dependence was not apparent. A group of different nitrogen-containing compounds was then studied. Here structure dependence was observed on all channels, ie carbon, oxygen and nitrogen. It was also noted that the responses became non-linear at higher concentrations. This would normally indicate detector overload, but not in this case as non-linearity occurred to different extents for the same element in different compounds. A study was also made on the effect of discharge tube ageing on response. Clean and dirty discharge tubes were used for the phenols and the nitrogen-containing compounds. The phenol, carbon and chlorine results showed a decreased sensitivity with the old tube, but the oxygen responses were not affected. The same drop in sensitivity was seen with the nitrogen-containing compounds, but here oxygen was also affected. Chapter 4 describes the use of the atomic emission detector and mass spectrometry as complementary techniques. Perfume samples were analysed using both instruments. A comparison of 'real' and 'fake' perfumes was also made. Results indicated that the atomic emission data was useful in deciding whether to accept or reject mass spectral library guesses. Chapter 5 describes the application of the atomic emission detector for the analysis of refinery streams. The use of the 'backamount' correction facility was also effectively demonstrated. Chapter 6 is a general discussion of the instrument including operational problems encountered and possible modifications to overcome these problems. The overall objective of the thesis is to place the GC-AED combination in the context of the commonly used chromatographic techniques.

First the method of gas-liquid chromatography (GLC) has been used to obtain partition coefficients, K, at infinite dilution on polymeric and non-polymeric phases. About 30-40 solutes were studied per stationary phase. Secondly the method of gas-solid chromatography has been used to obtain adsorption isotherms for a series of adsorbents by the technique of elution by characteristic point (ECP). A single injection of a gas or vapour suffices to obtain the isotherm, and then the limiting Henry's law constant, Kh, for adsorption at low surface coverage. About 20-30 solutes were studied per adsorbent. Experiments were carried out at several levels of relative humidity (RH) 0%, 31% and 53%. The solute compounds used were chosen so as to have a wide range of properties such as polarity (pi*2), hydrogen-bond acidity (alpha[H]2), and hydrogen-bond basicity (beta[H]2). The results as log partition coefficients or -log Henry's constants were analysed by multiple linear regression analysis using equations such as: -LogK[H] or LogK = SPo + s.pi* 2 + a.alpha[H]2 + b.beta[H]2 + 1. LogL[18] where L[18] is the solute Ostwald absorption coefficient on n-hexadecane. In this way, the selectivity of the liquid polymeric phase or solid adsorbent towards classes of compound was investigated and equations for the prediction of further values of LogK or LogK[H] formulated. In parallel with the measurement of partition coefficients on liquid polymeric phases by GLC in this work, partition coefficients for the polymers have been determined using surface acoustic wave (SAW) devices by coworkers at the Naval Research Laboratory, Washington. The results for a series of 8-9 solutes in six polymeric phases show that partition coefficients and patterns of responses predicted through GLC experiments are the same as those found experimentally using coated SAW devices. Hence GLC can be used to evaluate possible coating materials, and by the technique of multiple linear regression analysis, to predict SAW responses for a multitude of vapours.

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In Part I of this work, the decay of O₂(¹Δg) was studied at room temperature in the flow system in the absence of oxygen atoms. The decay of O₂(¹Δg) was classified into first and second order decay with respect to O₂(¹Δg). The rate constant of the main first order decay with respect to O₂(¹Δg), which is considered to be caused by collisions of O₂(¹Δg) with wall of the reaction tube, was found to be 0.25 sec. The total second order decay constant was found to be 2.9 x 10⁴ 1/ mole sec. In Part II the reactions of excited oxygen molecules with some olefins were investigated. 2,3-Dimethyl-3-hydroperoxybutene-1 was identified as the product of the reaction of excited oxygen molecules with 2,3-dimethylbutene-2, 3-Methyl hydroperoxybutene-1 and 2-methyl-3hydro-peroxybutene-1 were produced by the reaction of excited oxygen molecule with 2-methylbutene-2. The decay of O₂(¹Δg) with 2,3-dimethylbutene-2 was also studied but the results could not be explained by any simple mechanism. / Science, Faculty of / Chemistry, Department of / Graduate

Studies have been made of column efficiencies, extra-column effects, the liquid phase mass transfer term (C_l), and liquid phase distribution at ultra-low liquid loadings on glass bead gas-liquid chromatographic columns. The advantages of using lightly loaded columns are described in detail along with a critical evaluation of the limitations of this liquid phase reduction ad infinitum. Theories have been presented by Giddings^22,23,25,30,32 which predict the mass transfer term (C_l) as a function of two extreme liquid phase distributions. The first equation assumes 100% "capillary" liquid held at the glass bead contact points and represents a very inefficient column. This prediction is known to be valid for normal loaded columns in the 1.0 to 0.1 liquid percentage range^35,48. The second equation assumes a uniform liquid "adsorption" film around the glass bead which represents a very efficient condition. This equation has never been experimentally verified, but Hawkes^48 and Giddings^35 suggest that this condition is approached when the liquid phase is reduced and that a uniform film exists at loadings less than approximately 0.04%. The results of this research show that although a uniform film is approached with liquid load reduction, it is never reached, even at loadings as low as 0.004%. Data show that the capillary liquid assumption is valid for glass bead columns with liquid loadings greater than 0.05%, but fails to predict the proper efficiency term at the lower loadings. Two important transitions occur at about 0.03% liquid loading: (1) C_l ceases to decrease significantly with a liquid load reduction, and (2) C_l ceases to be the predominant (plate height controlling) efficiency parameter. Reductions below 0.03% do little to improve column efficiency and may cause adverse effects such as decreased resolution, increased adsorption, and a shorter column life. Data collected before and after some apparatus and procedure changes indicate the importance of minimizing extraneous peak broadening sources. It is suggested that a large amount of the literature is in error because of apathy in this area. The results suggest that a reduction in liquid load is an excellent method of increasing the column efficiency and reducing the analysis (sample retention) time.

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