| dc.description.abstract | Recently, there has been increasing interest in environmental analysis among the scientific community. Monitoring of organic and inorganic environmental pollutants and investigations into their potential to adversely affect human health has prompted the development of new methodologies for environmental analysis. Generally, the analytical procedure is comprised of several steps, such as sample collection, sample preparation, analysis, and data processing. Sample preparation is a critical step in the development of new methodologies, and considered the main source of uncertainty in the analysis of environmental samples. In this context, several sample preparation techniques have been recently developed and optimized with aims to miniaturize extraction, automate procedures, and reduce or circumvent solvent consumption. The currently presented research focused on further development and novel applications of two sample preparation methods, solid phase microextraction (SPME) and needle trap devices (NT).
Solid phase microextraction (SPME) combines sampling, sample preparation, and sample introduction in one step. Analytical sampling by SPME has been employed in a variety of environmental applications. To quantify target analyte content, different calibration approaches can be performed based on the application process. This method is an equilibrium-based sample preparation technique that due to its currently presented configuration provides only information related to free molecules in gas phase.
Conversely, the needle trap device, which contains a sorbent packed inside a needle, is an exhaustive, solventless, one-step sample preparation technique that can be easily calibrated. In addition, this approach eliminates errors associated with sample transportation and storage, which can consequently result in more accurate and precise analytical data. This technique is also useful for a wide variety of applications, including sample preparation of compounds with different chemical and physical properties, as well as varying volatilities. Furthermore, NT is a valuable sample preparation technique that, based on its geometry, allows it to act as a filter for collection of particles. The initial part of this research focused on new developments in the geometry of needle trap devices. Subsequently, particular attention was dedicated to the principles of collection efficiency as well as particle trapping mechanisms for filtration of particulate matter and aerosols by NTs. Finally, this thesis presents a joint application of NT and SPME for determination of target analytes in gaseous and particulate phases.
The first part of this thesis provides a thorough evaluation of new prototypes of the extended tip needle trap device (NT), and a summary of their application towards in vivo sampling of biological emissions, as well as active/passive on-site sampling of indoor air. To increase desorption efficiency, the newly proposed NT device was constructed with a side hole above the sorbent and an extended tip that fits inside the restriction of the narrow neck liner. The commercial prototype needles were packed with divinylbenzene particles and evaluated in terms of robustness after multiple uses, as well as extracted amounts of volatile organic compounds (VOCs). Successively, needles were packed in-lab with synthesized highly cross-linked PDMS as a frit to immobilize carboxen (Car) particles. The performance of needles packed with PDMS and Car were then compared in regards to different flow rates. For passive sampling, the needles were packed with Car particles embedded in PDMS in order to simplify calculations in passive mode. Good performance was obtained using the NT devices as spot samplers, as well as passive samplers under controlled conditions in the laboratory. Commercial modified prototypes of NT were used to study biogenic emissions of pine trees. The new lab-made NT was then applied in the analysis of indoor air in a polymer synthesis laboratory in both active and passive approaches.
Additionally, this thesis presents work conducted on the development and evaluation of an appropriate frit for NT devices. In order to investigate the feasibility of the NT device for analysis of nanometer-sized particles in high efficiency, three different filters, nanofibrous filter, porous membrane, and granular filter, were used to entrap dioctyl phthalate particles of diameters ranging between 10-200 nm. Subsequently, a series of experiments were carried out to estimate and compare the collection efficiency and pressure drop of the above mentioned filters. The effect of face velocity, fiber thickness, and fiber-packing density on filtration efficiency was also evaluated for each filter. The data showed that the efficiency curves for different filters demonstrated a lower efficiency for particle of sizes ranging between 40 to 60 nm, and at a face velocity of 17 cm/s. Calculated theoretical values based on the filtration model showed good agreement with the experimental data. This study demonstrated that use of the nanofibrous filter led to a significant improvement in the filtration efficiency of the NT device. Nevertheless, the proposed porous membrane was chosen as an appropriate filter instead for subsequent studies due to its relative simplicity of packing through the needle trap devices and high reproducibility in regards to packing procedure in comparison to the nanofribrous filter, which has high efficiency and poor reproducibility.
Finally, needle-trap (NT) devices were applied in conjunction with solid phase microextraction (SPME) towards the measurement of free and particle-bound fragrances derived from personal care products. In order to simulate in-use exposure scenarios, the experiments were conducted in a specially constructed 0.1 m3 chamber configured to simulate in-use conditions in a bathroom. The perfumed body spray was introduced to the chamber in three second bursts to mimic typical consumer use. The produced aerosol was then continuously monitored using a scanning mobility particle sizer (SMPS) to determine the number and size of particles; characterization of the aerosol size distribution is an important factor when considering risk assessment, as particles <7µm are considered respirable and those of size <20 µm inhalable. Needle trap devices using a range of packing materials were evaluated for measurement of total concentrations of target analytes, while free concentrations of the fragrance present in the aerosol spray were determined concurrently by SPME based on the external calibration method. The results showed similar concentration trends with the same sampling devices over different days. | en |
