Mathematically modeling chromatograms of evaporated ignitable liquids for fire debris applications

Smith, Ruth; Brehe, Rebecca J.; McIlroy, John W.; McGuffin, Victoria L.

doi:10.1016/j.forc.2016.08.005

Cited by 17 publications

(7 citation statements)

References 15 publications

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“…Retention index is a useful surrogate for physical properties such as vapor pressure or boiling point, as it can be readily determined without requiring knowledge of the identity or concentration of compounds in the liquid. The success of the kinetic-based model in predicting chromatograms corresponding to evaporated petroleum distillates has also been demonstrated [21].…”

Section: Introductionmentioning

confidence: 98%

“…As the kinetic model was developed based on empirical evaporation rate constants determined at a fixed temperature, the effect of temperature on the kinetics of evaporation was not taken into account [17,21]. Recent work by Birks et al reported the unexpected effect of elevated temperature on the evaporation of gasoline, highlighting the importance of temperature in any predictive model [22].…”

Section: Introductionmentioning

confidence: 99%

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Fixed- and Variable-Temperature Kinetic Models to Predict Evaporation of Petroleum Distillates for Fire Debris Applications

2018

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Forensic fire debris analysis focuses on the identification of a foreign ignitable liquid in debris collected from the scene of a suspected intentional fire. Chromatograms of the extracted debris are compared to a suitable reference collection containing chromatograms of unevaporated and evaporated ignitable liquids. However, there is no standardized method for the evaporation of ignitable liquids and the process itself can be time consuming, which limits the number of chromatograms of evaporated liquids included in the reference collection. This work describes the development and application of a variable-temperature kinetic model to predict evaporation rate constants and mathematically predict chromatograms corresponding to evaporated ignitable liquids. First-order evaporation rate constants were calculated for 78 selected compounds in diesel, which were used to develop predictive models of evaporation rates. Fixed-temperature models were developed to predict the rate constants at five temperatures (5, 10, 20, 30, 35 °C), yielding a mean absolute percent error (MAPE) of 10.0%. The variable-temperature model was then created from these data by multiple linear regression, yielding a MAPE of 16.4%. The model was applied to generate a reference collection of predicted chromatograms of diesel and kerosene corresponding to a range of evaporation levels. Using the modeled reference collection, successful identification of the liquid and level of evaporation in a test set of chromatograms was demonstrated.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Fixed- and Variable-Temperature Kinetic Models to Predict Evaporation of Petroleum Distillates for Fire Debris Applications

2018

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“…Most recent ignitable liquid studies have focused on applying chemometrics , likelihood ratios or mathematical modeling to ignitable liquid analysis. Smith et al.…”

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confidence: 99%

“…Smith et al. compared experimentally evaporated gasoline (30–90% by mass) to model chromatograms and found only a moderate correlation (0.772) for gasoline that was 90% evaporated. Vergeer et al.…”

mentioning

confidence: 99%

“…Most recent ignitable liquid studies have focused on applying chemometrics (10)(11)(12)(13)(14)(15), likelihood ratios (16) or mathematical modeling (17,18) to ignitable liquid analysis. Smith et al (17) compared experimentally evaporated gasoline (30-90% by mass) to model chromatograms and found only a moderate correlation (0.772) for gasoline that was 90% evaporated. Vergeer et al applied numerical likelihood ratios for comparison of up to 75% evaporated gasoline and found two distance functions perform better, while still not showing 100% correlation, than the multivariate method.…”

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confidence: 99%

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Determining the Method Threshold of Identification via Gas Chromatography–Mass Spectrometry of Weathered Gasoline Extracted from Burnt Nylon Carpet,

Hondrogiannis

Newton

Alibozek

2019

Journal of Forensic Sciences

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The Organization of Scientific Area Committees defines threshold of identification as the minimum concentration of ignitable liquid identifiable from gas chromatographic‐mass spectrometry data using accepted pattern identification criteria. We propose a method for determining this threshold for gasoline based on base peak to qualifier ratios of six compounds. The ion ratios were established for each compound in the neat gasoline. These ratios were then compared to those obtained for gasoline and 98% weathered gasoline both spiked onto burnt nylon carpet at 20 ppt down 0.50 ppt, and recovered from the carpet using headspace extraction (ASTM 1412). Identification was confirmed if the compounds’ ion ratios fell within ±25% of that in the neat sample. We found that ion ratios for all samples were acceptable for six compounds at 1.60 and 0.80 ppt for extracted neat and extracted 98% weathered gasoline, respectively, illustrating potential for incorporating into Quality Assurance Programs.

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Chemometric applications in fire debris analysis

Sigman

Williams

2020

WIREs Forensic Science

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Chemometric applications related to the analysis of ignitable liquids (ILs) and fire debris samples have evolved over the last 30 years. Most older papers focused on the use of chemometrics for classification of ILs by manufacturer, grade or into classes defined by the American Society for Testing and Material (ASTM) standard test method ASTM E1618. More recently, chemometric studies in fire debris analysis have focused on estimating the strength of the evidence in the form of a likelihood ratio (LR). The progression of chemometric methods from simple classification tasks to the calculation of LRs and statements of evidentiary value has implications across all disciplines of forensic science. Most of the data analyzed by chemometric methods in forensic fire debris analysis come from gas chromatography–mass spectrometry, although several studies have examined data from head space‐mass spectrometry and other sensors. Retention time alignment is a challenge that must be addressed if chemometric methods are intended to have interlaboratory applicability. Several of the reports reviewed here rely on data representations that avoid retention time alignment issues. Attempts to apply chemometric methods to the analysis of ILs and fire debris samples has for the most part been an academic exercise and the results have not made their way into accredited forensic laboratories and established protocols. The chemometric methods are well‐founded in statistical principles and they can provide a means of strengthening forensic fire debris analysis in the future. This article is categorized under: Forensic Chemistry and Trace Evidence > Fire Debris Analysis Forensic Chemistry and Trace Evidence > Trace Evidence Forensic Chemistry and Trace Evidence > Presentation and Evaluation of Forensic Science Output

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Mathematically modeling chromatograms of evaporated ignitable liquids for fire debris applications

Cited by 17 publications

References 15 publications

Fixed- and Variable-Temperature Kinetic Models to Predict Evaporation of Petroleum Distillates for Fire Debris Applications

Fixed- and Variable-Temperature Kinetic Models to Predict Evaporation of Petroleum Distillates for Fire Debris Applications

Determining the Method Threshold of Identification via Gas Chromatography–Mass Spectrometry of Weathered Gasoline Extracted from Burnt Nylon Carpet,

Chemometric applications in fire debris analysis

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