Accurate and rapid discrimination of cigarette and household decoration material ash residues by negative chemical ionization TOFMS via acid-enhanced evaporation

Shujun Liu,Ximing Song,Yuanyuan Xie

doi:10.1038/s41598-020-62814-1

Shujun Liu, Ximing Song + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-62814-1

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Abstract

The detection and identification of cigarette ash in fire debris can be meaningful in fire investigations caused by burning cigarettes. In this work, a novel analytical method based on negative chemical ionization time-of-flight mass spectrometry (NCI/TOFMS) combined with a phosphoric-acid-enhanced evaporation strategy has been developed for the discrimination of cigarette ash samples (CAs) and common household decoration material ash samples (CHDMAs). A series of characteristic ions representing the acidified products HNCO and formic acid in the CAs were achieved, whose signal responses were enhanced with the help of mechanical agitation operation. To account for both the signal responses of the characteristic ions and acid corrosion of the ion source, the dynamic-purge gas was chosen to be 200 mL/min. The whole time for analysis was only 5 min, which is suitable for high-throughput measurements of large quantities of fire debris. As a result, a preliminary discrimination was achieved between the CAs and CHDMAs by virtue of the chemometric tool of principal components analysis (PCA) based on intensity differences of the characteristic ions. The results are encouraging and highlight the potential of NCI/TOFMS without complicated sample preparation steps for the accurate and high-throughput identification of cigarette ash on substrates in fire debris.

Highlights

It is well known that arson leads to property damage, loss of life, and feelings of insecurity in the community
The characteristic ions at m/z = 42, 75, 85, and 88 were identified as the ions NCO−, HNCO·O2−, HNCO·NCO− and [HCOOHNCO]−, respectively, after the mass-to-charge calibration in Table 1, all of which were relevant to HNCO
Most of produced HNCO in the cigarette ash was suspected to be in the form of acid radicals after combustion because the HNCO molecules would volatilize into the smoke with a relatively high temperature

Summary

Introduction

It is well known that arson leads to property damage, loss of life, and feelings of insecurity in the community. Headspace-mass spectrometry electronic nose (E-Nose) was proposed for the analysis of ILRs, including the investigation of fire suppression agents and weathering process on ILs with fast determination capabilities, no solvent and absorbent requirement, and easy operation[12,13,14,17,18]. To solve the problem of GC-MS being time-consuming, a new method using direct analysis in real-time mass spectrometry (DART-MS) without extraction was developed for the fast identification of ILs from substrates[15]. Along with the analytical methods mentioned above, there are generally sample preparation procedures for extracting and concentrating volatile organic compounds (VOCs) from ILRs with complicated substrate materials in fire debris[3,6]. Non-volatile, polar organic compounds in cigarette ash samples were investigated to differentiate three cigarette brands for forensic purposes based on GC-MS/MS46. The acid radicals inherent in the cigarette ash accompanying the trace metals may be used for distinguishing the cigarette ash from other material ash residues

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