Browsing by Subject "SPME"

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    Design and implementation of gas chromatography-mass spectrometry (GC-MS) methodologies for the analysis of thermally labile drugs and explosives
    (2016-11-18) Ash, Jordan R.; Goodpaster, John V.
    Gas Chromatography/Mass Spectrometry (GC/MS) is an analytical technique that sees frequent use in labs across the world. It is also one of the most common instruments found in forensic science laboratories. This technique can efficiently and accurately separate and identify a broad range of compounds that may be present in evidence submitted for analysis. In this work, the versatility of this instrument was applied to new methodologies for the detection of explosives and illicit drugs. The analysis of explosives by GC/MS is common but can be problematic. The thermally sensitive nature of some explosives can cause them to degrade when introduced to the high temperatures of a GC/MS inlet. This project looked at the design and implementation of a way to separate and detect a variety of nitrate ester explosives in a short amount of time. In addition to this, a new technique known as Total Vaporization-Solid Phase Microextraction (TV-SPME) was utilized as a pre concentration technique. The parameters for TV-SPME were statistically optimized for a low level of detection. The combination of these areas allowed for the separation of ethylene glycol dinitrate, nitroglycerin, erythritol tetranitrate, and pentaerythritol tetranitrate with a detection limit as low as 50 parts per trillion (ppt). Degradation products such as 1-mononitroglycerin, 1-3-dinitroglycerin, and 2-mononitroglycerin were also successfully identified. The problem of thermally labile compounds extends to the world of illicit drugs. In the second project, several derivatization schemes were developed for common controlled substances. N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS) was used for silylation, trifluoroacetic anhydride (TFAA) was sued for acylation, and (N,N-Dimethylformamide dimethyl acetal (DMF-DMA) for alkylation. Three different compound classes totaling 15 different drugs were investigated. N,N-Dimethylformamide dimethyl acetal (DMF-DMA) is presented as a novel way of derivatizing several drugs of interest. Primary amines and zwitterions were derivatized with this reagent to much success, specifically: amphetamine, 2-(4-Iodo-2,5-dimethoxyphenyl)ethan-1-amine (2C-I), pregabalin, and gabapentin.
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    Solid-Phase Microextraction of Volatile Organic Compounds for Analytical and Forensic Applications
    (2023-12) Davis, Kymeri Elizabeth; Goodpaster, John; Frédérique, Deiss; Nicholas , Manicke; Sébastien , Laulhé
    Gas chromatography-mass spectrometry (GC-MS) is a frequently used technique in forensic chemistry for the identification of controlled substances and explosives. GC-MS can be coupled with solid-phase microextraction (SPME), in which a fiber with a sorptive coating is placed into the headspace above a sample or directly immersed in a liquid sample. Analytes are adsorbed onto the fiber which is then placed inside the heated GC inlet for desorption. Illicit drugs are often found in the form of impure solids, mixed with other drugs, adulterants, and diluents. A simple method for the quick identification of drugs including methamphetamine, cocaine, heroin, fentanyl, and pharmaceutical tablets was developed. Headspace SPME methods were utilized with an elevated extraction temperature for the detection of various drugs in powder and tablet form. An extraction temperature of 120oC was used to encourage analytes into the headspace of the vial. A sample of the solid drug was placed in a headspace vial with no prior sample preparation or clean-up. This vial was then heated inside of an agitator where the sample was extracted. It was found that drugs in solid and tablet form can be detected using this high temperature headspace SPME method at the temperature of 120oC with no prior sample preparation. This method is simple, efficient, and cost effective for the detection of legal and illicit drugs in solid form. Headspace SPME may also be used for the analysis of explosive materials. Canines trained at detecting hidden explosives should be trained using real explosive materials that have minimal contamination by other explosive odors to ensure accurate identification of potential threats. Therefore, the potential for cross-contamination between training aids is of importance. There are various storage methods in use by canine handlers such as plastic and cloth bags, but these can lead to cross-contamination between training aids during storage. Alternatively, odor-permeable membrane devices (OPMDs) may store training aides and be used as a delivery device. A membrane in the OPMD allows for volatile compounds from the training aids to be released during training while helping to prevent contaminants from entering the device. OPMDs were used in addition to traditional storage containers to monitor the contamination and degradation of 14 explosives used as canine training aids. Samples included explosives that contain highly volatile compounds like dynamite and explosives with less volatile compounds like RDX. Explosives were stored individually using traditional storage bags or inside of an OPMD at two locations, IUPUI and an Indianapolis Metropolitan Police Department. The police department actively used the training aids during canine trainings. Samples from each storage type at both locations were collected at 0, 3, 6, and 9 months and analyzed using Fourier transform infrared (FTIR) spectroscopy and GC-MS with SPME. FTIR analyses showed no signs of degradation of the training aids from any timepoint or location. GC-MS identified cross-contamination from ethylene glycol dinitrate and/or 2,3-dimethyl-2,3-dinitrobutane across almost all samples regardless of storage condition. The contamination was found to be higher among training aids that were stored in traditional ways and were in active use by canine teams. Additionally, Time 0 had the highest level of contamination, indicating that explosive training aids are received from the vendors with initial cross-contamination. To test the initial cross-contamination levels of training aids, 11 explosive materials were ordered from three different vendors. A 1-gram sample of each was collected and analyzed using SPME with GC-MS. In several cases, explosive materials that are commercially available already exhibit elevated levels of contamination. This indicates that training aids must be acquiring contamination during manufacturing and/or storage at the vendor facility. The cross-contamination of explosive canine training aids stored in OPMDs was further evaluated and compared to traditional storage methods. This was done by storing various combinations of storage containers such as cloth bags, velcro bags, and OPMDs along with explosives and using activated charcoal strips to collect the volatile compounds such as 2,3-dimethyl-2,3-dinitrobutane and ethylene glycol dinitrate. Only one type of storage container, a velcro bag, showed evidence of contamination, indicating that OPMDs may not further prevent cross-contamination of explosive training aids.