Halogen tagging derivatization reactions and analysis of halogenated hydrocarbons by gas chromatography element specific detection

• Main Author: Hardas, Nitin Ramkrishna
• Language: ENG
• Published: ScholarWorks@UMass Amherst 1998
• Subjects: Analytical chemistry|Petroleum production|Organic chemistry
• Online Access: https://scholarworks.umass.edu/dissertations/AAI9823743

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.