An Exercise in General, Organic and Biochemistry to Stress the Importance of Math Mindfulness and Critical Thinking to Nursing Students

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 27 (2022) pp 33-43

Combining Gas Chromatography-Mass Spectrometry and Principal Component Analysis to Facilitate Complete Detection and Identification of Ignitable Liquids

Victoria Sedwick, Anne Leal, Gregory A. Barding Jr. , Kim Nelson, David Pollard, A Bakarr Kanu*

1Department of Chemistry, Winston-Salem State University, Winston-Salem, NC 27110 2Chemistry and Biochemistry Department, California State Polytechnic University, Pomona, CA 91768 3Department of Chemistry, Wake Forest University, Winston-Salem, NC 27101 Email: kanuabb@wssu.edu

Received December 19, 2020. Accepted February19, 2022.

Published: 27 May 2022

Abstract. This paper reports an approach that developed instrumental parameters with two different GC-MS instruments. Data from the two devices were combined with principal component analysis (PCA) to analyze genuinely and ignited ignitable liquid residues (ILR). We simulate the field samples by burning seasoned pinewood soaked with each ignitable liquid (IL). Enough unburnt components from an IL remained on the burnt wood. These components were enough to reveal the chromatographic fingerprint of an IL. Most importantly, the chromatographic profile from a pure IL and IL poured onto a wooden substrate and ignited was identical. The chromatographic profiles reported from each instrument for each IL were reproducible to within 3% RSD. The MS data from both GC-MS instruments showed similar m/z peaks from all ILs, indicating similar hydrocarbon(s) and or fragmentation cluster patterns in the ILs studied ingredients. The PCA data showed characteristic differences giving rise to the separation between incendiaries, albeit some were overshadowed by clustering. In some cases, ILs that showed similar components in their mass spectra profile grouped as a class on the PCA display. We demonstrate an approach using direct headspace injection to individualize ILs recovered from crime scenes. Direct headspace injection and GC-MS combined with PCA are shown as promising facile methods for the qualitative determination of specific ILs in real-world arson samples. Initially, our project started as an undergraduate instrumental analysis guided-inquiry (GI) project. Such labs have been reported to enhance student learning and improve students' critical and problem-solving abilities. We plan to incorporate this approach in both an undergraduate instrumental analysis class and a graduate-level analytical chemistry class.

Key Words: KW Laboratories and Demonstrations; forensic chemistry;gas chromotagraphy-mass spectrometry; ingnitable liquids

(*) Corresponding author. (E-mail: kanuabb@wssu.edu )

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