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Browsing by Subject "Gas Chromatography-Mass Spectrometry"
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Item Chemometric Analysis of Volatile Organic Compound Biomarkers of Disease and Development of Solid Phase Microextraction Fibers to Evaluate Gas Sensing Layers(2022-08) Woollam, Mark David; Agarwal, Mangilal; Deiss, Frédérique; Goodpaster, John; Naumann, ChristophCanines can detect different diseases simply by smelling different biological sample types, including urine, breath and sweat. This has led researchers to try and discovery unique volatile organic compound (VOC) biomarkers. The power of VOC biomarkers lies in the fact that one day they may be able to be utilized for noninvasive, rapid and accurate diagnostics at a point of care using miniaturized biosensors. However, the identity of the specific VOC biomarkers must be demonstrated before designing and fabricating sensing systems. Through an extensive series of experiments, VOCs in urine are profiled by solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) to identify biomarkers for breast cancer using murine models. The results from these experiments indicated that unique classes of urinary VOCs, primarily terpene/terpenoids and carbonyls, are potential biomarkers of breast cancer. Through implementing chemometric approaches, unique panels of VOCs were identified for breast cancer detection, identifying tumor location, determining the efficacy of dopaminergic antitumor treatments, and tracking cancer progression. Other diseases, including COVID-19 and hypoglycemia (low blood sugar) were also probed to identify volatile biomarkers present in breath samples. VOC biomarker identification is an important step toward developing portable gas sensors, but another hurdle that exists is that current sensors lack selectivity toward specific VOCs of interest. Furthermore, testing sensors for sensitivity and selectivity is an extensive process as VOCs must be tested individually because the sensors do not have modes of chromatographic separation or compound identification. Another set of experiments is presented to demonstrate that SPME fibers can be coated with materials, used to extract standard solutions of VOCs, and analyzed by GC-MS to determine the performance of various gas sensing layers. In the first of these experiments, polyetherimide (PEI) was coated onto a SPME fiber and compared to commercial polyacrylate (PAA) fibers. The second experiment tuned the extraction efficiency of polyvinylidene fluoride (PVDF) - carbon black (CB) composites and showed that they had higher sensitivity for urinary VOC extraction relative to a polydimethylsiloxane (PDMS) SPME fiber. These results demonstrate SPME GC-MS can rapidly characterize and tune the VOC adsorption capabilities of gas sensing layers.Item Critical Comparison of Total Vaporization- Solid Phase Microextraction vs Headspace- Solid Phase Microextraction(2021-05) Train, Alexandra; Goodpaster, John; Manicke, Nicholas; Picard, ChristineSolid Phase Microextraction (SPME) is a popular sampling technique that can be paired with Gas Chromatography/Mass Spectrometry (GC-MS). SPME-GC-MS is used in forensic chemistry due to its simplification of the sample preparation process. Headspace-Solid Phase Microextraction (HS-SPME) is a technique where the sample is heated to generate volatiles in the headspace of the vial. A SPME fiber is then inserted into the vial and the compounds in the headspace will bind to the fiber. Total Vaporization- Solid Phase Microextraction (TV-SPME) is a technique that is derived from the HS-SPME technique. In Chapter 1, the critical comparison of HS-SPME and TV-SPME is discussed. Samples including marijuana, essential oils, and CBD oil were utilized to compare the two techniques. The compounds of interest in marijuana are the three main cannabinoids: cannabinol (CBN), cannabidiol (CBD), and tetrahydrocannabinol (THC). The sample preparation and GC-MS parameters were kept the same for all samples to determine which SPME technique works best for these sample types and yielded the greatest sensitivity. It was found that HS-SPME shows greater sensitivity with CBN and equivalent sensitivity with essential oils, THC and CBD. In Chapter 2, the detection of synthetic cannabinoids utilizing liquid-liquid injection as well as HS-SPME and TV-SPME is discussed. The detection of these compounds is important because this type of drug has become more prevalent in the United States because they can be chemically altered slightly so they still have the effects of a drug but can evade drug legislation. The detection of synthetic cannabinoids using liquid injection was found to be successful but detection using HS-SPME and TV-SPME was found to be unsuccessful. In Chapter 3, the analyses of real and artificial saliva utilizing HS-SPME and TV-SPME is discussed. Determining the compounds present in real saliva and artificial saliva will be of importance for future research into determining if the presence of drugs in saliva can be analyzed with these techniques. The analyses of real and artificial saliva were found to be successful using HS-SPME, without derivatization, and TV-SPME, with and without derivatization. Many of the compounds present in the real saliva were detected and were confirmed to be compounds regularly found in saliva by other scientific literature.Item Detection of Illicit Drugs in Various Matrices Via Total Vaporization Solid-Phase Microextraction(2019-08) Davis, Kymeri Elizabeth; Goodpaster, John; Manicke, Nicholas; Deiss, FrédériqueIn Headspace Solid-Phase Microextraction (Headspace SPME), a sample is heated to encourage a portion of the analyte into the headspace of a vial. A coated fiber is introduced into the sample headspace and the analyte is adsorbed onto the fiber coating. Total Vaporization Solid-Phase Microextraction (TV-SPME) is a technique that is derived from this technique. In TV-SPME, liquid samples are completely vaporized allowing for better adsorption and fewer matrix effects. This method does not require any sample preparation, utilizes minimal supplies and can be automated, making it both an efficient and cost-effective method. Chapter 1 will discuss the theory of SPME and TV-SPME. In Chapter 2, the detection of ɣ-hydroxybutyric acid (GHB) and ɣ-butyrolactone (GBL) in beverages is discussed. The detection of these compounds in beverages is of importance because these drugs may be used to facilitate sexual assault. This crime utilizes substances that cause sedation and memory loss. The derivatization of GHB as well as the properties that make GHB difficult to detect will be discussed. Chapter 3 will discuss the detection of methamphetamine and amphetamine (as their trifluoroacetyl derivatives), GBL, and the trimethylsilyl derivative of GHB in human urine. Amphetamine is a metabolite of methamphetamine, therefore, both drugs should be identified within biological samples. GHB and GBL are metabolites of one another and interconvert when in aqueous solution. This interconversion will be discussed. Chapter 4 will cover method optimization of the Total Vaporization Solid-Phase Microextraction method. Analytes of interest for these analyses were methamphetamine, amphetamine, GHB, and GBL. The optimal extraction temperature ranging from 60-160°C of each drug will be discussed as well as why higher temperatures may not be suitable for this method. A limit of detection study for methamphetamine and amphetamine will also be covered. Chapter 5, the future work chapter, will discuss future analyses using the Total Vaporization Solid-Phase Microextraction method including the analysis of powder materials, plant material, and toxicological samples. Powder material will include the analysis of individual powdered drugs as well as realistic drug mixtures. Some analyses on individual powder samples has already been completed and will be shown. Plant material will include the analysis of naturally occurring compounds found in marijuana plants as well as synthetic cannabinoids. Toxicological samples will expand on previously mentioned urine samples to include drugs such as benzoylecgonine and THC-COOH.