GC/MS and DART-MS as complementary methods for investigating the effects of weathering on chemical profiles of ignitable liquids: A case study for paint thinner

• NCJ Number: 306077
• Journal: Forensic Chemistry Volume: 33 Dated: May 2023 Pages: 100478
• Author(s): Shruthi Perna; Briza Marie Dedicatoria; Ngee Sing Chong; Mengliang Zhang
• Date Published: May 2023
• Grant Number(s): 2020-DQ-BX-0003
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical)
• Award: Detection of Ignitable Liquid Residues in Fire Debris by Using Direct Analysis in Real Time Mass Spectrometry (DART-MS)

Annotation

This study used gas chromatography/mass spectrometry (GC/MS) and direct analysis in real time mass spectrometry (DART-MS) were used to analyze paint thinner samples weathered under different conditions.

Abstract

As GC/MS total ion chromatograms (TIC) of weathered paint thinner samples varied significantly due to the disparate evaporation rates of organic compounds in the mixture, DART-MS spectra have shown more consistent profiles among different samples. The distinctive ion clusters identified in the DART-MS spectra were attributed to the less volatile glycol ethers and polymeric compounds with alkyl chains in the paint thinner samples. Analysis of variance-principal component analysis (ANOVA-PCA) was applied to study the contributions of weathering degree and temperature factors to the total variance of GC/MS TIC and DART-MS spectral datasets and found that both factors played significant roles in the weathering process (p < 0.05), though weathering degree contributed to considerably more total variance to GC/MS TIC profiles (i.e., 93.4 %). The paint thinner GC/MS and DART-MS profiles were compared with those from other common ignitable liquids, such as gasoline, torch fuel, lighter fluid, and Japan drier. The partial least squares discriminant analysis (PLS-DA) models were constructed to classify the ignitable liquids with the classification rates of 99.97 ± 0.02 % and 99.80 ± 0.08 % for models based on GC/MS and DART-MS data, respectively. This study has shown that DART-MS can provide discriminative information for distinguishing ignitable liquid samples and complement the existing GC/MS method by the detection of less volatile compounds. (Published abstract provided)