Characterization of Biodegraded Ignitable Liquids by Headspace–Ion Mobility Spectrometry

Abstract

The detection of ignitable liquids (ILs) can be crucial when it comes to determining arson cases. Such identification of ILs is a challenging task that may be affected by a number of factors. Microbial degradation is considered one of three major processes that can alter the composition of IL residues. Since biodegradation is a time related phenomenon, it should be studied at different stages of development. This article presents a method based on ion mobility spectroscopy (IMS) which has been used as an electronic nose. In particular, ion mobility sum spectrum (IMSS) in combination with chemometric techniques (hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA)) has been applied for the characterization of different biodegraded ILs. This method intends to use IMSS to identify a range of ILs regardless of their degree of biodegradation. Three ILs (diesel, gasoline and kerosene) from three different commercial brands were evaluated after remaining in a soil substrate for several lengths of time (0, 2, 5, 13 and 38 days). The HCA results showed the samples’ trend to fall into categories characterized by ILs type and biodegradation time. The LDAs allowed a 99% successful classification of the samples according to the IL type. This is the first time that an HS-IMS technique has been used to detect ILs that have undergone biodegradation processes. The results show that IMS may be a promising alternative to the current standard method based on gas-chromatography for the analysis of biodegraded ILs. Furthermore, no pretreatment of the samples nor the use of a solvent is required.

Assessment of Volatile Compound Transference through Firefighter Turnout Gear

“…The results from HS-GC-IMS were processed as previously reported for transformation to Ion Mobility Sum Spectra (IMSS), which has produced very good results in the detection and discrimination of fire debris and PDP samples [ 34 , 35 , 36 , 37 ]. Once the data matrix was obtained, the drift times were normalized to the reaction ion peak (RIP) with LAV software (G.A.S., Dortmund, Germany), using the ionized water signal as the signal of reference.…”

“…This technique has already been successfully applied in the chemical detection of warfare agents, agents that cause blisters (mustard gases or lewisite), and asphyxia agents (phosgene) [ 32 , 33 ]. Furthermore, HS-GC-IMS systems have been used in the detection and discrimination of fire debris, allowing the detection of its presence and subsequent characterization, even when it has been exposed to biodegradation processes [ 34 , 35 , 36 ].…”

Discrimination of Ignitable Liquid Residues in Burned Petroleum-Derived Substrates by Using HS-MS eNose and Chemometrics

“…Aliaño-González et al have used the ion mobility spectrum obtained from the headspace for the identification of IL in fire debris [ 28 ]. In similar way, P. Calle et al have recently used the ion mobility spectrum in combination with linear discriminant analysis (LDA) to characterize biodegraded ILs [ 29 ].…”

A Novel Method Based on Headspace-Ion Mobility Spectrometry for the Detection and Discrimination of Different Petroleum Derived Products in Seawater

“…On the other hand, ion mobility spectrometry (IMS) has been successfully applied for a large variety of purposes, such as food fraud detection [ 36 , 37 , 38 , 39 ], fire debris analysis [ 40 , 41 ], and also to uncover drugs and explosives [ 42 , 43 , 44 ]. As regards environmental issues, IMS has mainly been used to detect bacterial contamination [ 45 , 46 , 47 ], to characterize biodegraded PDPs [ 48 ] and, in combination with extraction techniques, to identify polycyclic aromatic hydrocarbons in water [ 49 , 50 ]. IMS exhibits a very low limit of detection (within the µL·L −1 range), and it does not require complex sample preparation methods [ 51 ].…”

“…Lastly, IMS operates at atmospheric pressure, which means that IMS can be used for the real-time monitoring of the analysis procedures and, therefore, could be applied for the detection of PDPs spills in water. On the other hand, the IMS technique can be used as a multiple sensor device, in which each drift time in the detector acts as a specific “sensor” and the total volatile compounds intensity collected at each drift time is equivalent to multiple sensor signals [ 36 , 40 , 48 , 53 , 54 , 55 ].…”