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Development of supercritical fluid and solid-phase extraction methods for the determination of primary aromatic amines in environmental samples

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Description: Development and evaluation of sample preparation techniques for the determination of 1,4-phenylenediamine, 2,4-diaminotoluene, benzidine, 4,4$\sp\prime$-methylenebis(2-chloroaniline), 3,3$\sp\prime$-dimethylbenzidine and 3,3$\sp\prime$-dichlorobenzidine in environmental samples was conducted. The goal was to develop extraction methods which performed better than the United States Environmental Protection Agency (USEPA) procedures, utilizing techniques which eliminate the necessity for large volumes of solvent. A supercritical fluid extraction (SFE) method was developed for soil samples, and a solid-phase extraction (SPE) method was developed for water samples. An evaluation of the EPA sonication extraction method concluded that it was not effective for extraction of aromatic amines from soils. SFE was demonstrated to be a viable alternative to sonication extraction. However, types of matrices appeared to be critical to recovery for both extraction techniques. The development and optimization of a SFE method for the determination of aromatic amines in soil matrices was presented. Parameters investigated included the use of chemical modifiers, pressure, temperature, and time. The novel modifier 1,6-hexanediamine was demonstrated to be effective at improving extraction efficiency. The mechanism likely involves blocking of reactive sites and release of adsorbed analytes through exchange. An extensive comparison of the optimized SFE method with sonication extraction was presented. The SFE method yielded significantly higher recoveries and equivalent or better precision than sonication extraction for eleven matrices studied. Characterization data for these matrices was evaluated to determine characteristics which affect primary aromatic amine recovery and to study the potential mechanisms involved in adsorption on the soil. It was determined that amine recovery was affected by the percent clay, the surface area, and the cation exchange capacity of the soil. Adsorption likely involves cation exchange groups including silanols on the surface of the clay materials in the soil. The extraction of primary aromatic amines from aqueous samples was also studied. Five different adsorbents were evaluated for solid-phase extraction (SPE) in the reversed-phase mode. An SPE method utilizing styrene/divinylbenzene copolymer was developed, and compared to USEPA separatory funnel and continuous liquid-liquid extraction techniques. Significantly better recoveries were obtained on fortified water samples using SPE.
Language: English
Format: Degree Work