|Abstract or Summary
- The development of analytical methods for emerging contaminants creates many unique challenges for analytical chemists. By their nature, emerging contaminants have inherent data gaps related to their environmental occurrence, fate, and impact. This dissertation is a compilation of three studies related to method development for the structural identification of emerging contaminants, the detection and quantification of chemicals used in unprecedented quantities and applications, and the extraction of compounds from complex matrices where the solvent-solute-matrix interactions are not completely understood. The three studies present analytical methods developed for emerging contaminants in complex matrices, including: fluorochemical surfactants in aqueous film-forming foams, oil dispersant surfactants in seawater, and fullerene nanomaterials in carbonaceous solids.
Aqueous film-forming foams, used in military and commercial firefighting, represent environmentally-relevant commercial mixtures that contain a variety of fluorochemical surfactants. Combining the surfactant-selective ionization of fast atom bombardment mass spectrometry with high resolution mass spectrometry, chemical formulas for 11 different fluorochemical classes were identified. Then AFFF-related patents were used to determine the structures. Of the eleven classes of fluorochemicals, ten have little, if any, data on their environmental occurrence, fate, and potential impacts in the peer-reviewed literature. In addition, nine of the identified classes had either cationic or zwitterionic functionalities and are likely to have different transport properties compared to the well-studied anionic fluorochemicals, such as perfluorooctanoate.
After the Deepwater Horizon oil spill in the summer of 2010, one of the emergency response methods for the mitigation of the oil's environmental impact was the use of unprecedented amounts of oil dispersant to break down the oil slick and encourage biodegradation. This event illustrated the need for rapid analytical method development in order to respond to the potential environmental disaster in a timely manner. Using large volume injection liquid chromatography with tandem mass spectrometry, an analytical method was developed for the trace analysis of the multiple dispersant surfactant classes and the potential degradation products of the primary surfactant. Limits of detection ranged from 49 – 3,000 ng/L. The method provided excellent recovery (86 – 119%) and precision (10 – 23% RSD), while also accommodating for the high salinity of seawater samples and analyte contamination.
Despite the fact that fullerene nanomaterials have been studied for almost three decades, research is still being conducted to fully understand the environmental properties of these materials. Previous studies to extract fullerenes from environmental matrices have resulted in low efficiency, high variability, or the extraction efficiencies have gone unreported. Extraction by ultrasonication with toluene and 1-methylnaphthalene increased the recovery 5-fold of a spiked, isotopically-labeled C₆₀ surrogate from carbon lampblack as compared to that of the conventional approach of extracting with 100% toluene. The study revealed the importance of evaluating experimental variables such as extraction solvent composition and volume, and sample mass, as they have a significant impact on the quantitative extraction of fullerenes from environmental matrices.