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

Abstract

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.

Very High Resolution Tools for the Monitoring and Assessment of Environmental Hazards in Coastal Areas

“…The intensity will be adjusted depending on the degradation of the specific type of oil. According to McIlroy et al (2018) and Butler (1976), the fraction of the original diesel compound remaining after evaporation can be adjusted to a kinematic law:…”

Evaporation Kinetics of Liquid Mixtures and Safe Handling

“…k 1 only quantifies the dynamics of the process under the specific measuring conditions (temperature, pressure, or gas–liquid interfacial fluxional area). Other authors have previously reported first-order phenomenology for the late evaporation stage of liquid mixtures. − , …”

“…Other authors have previously reported first-order phenomenology for the late evaporation stage of liquid mixtures. [9][10][11][12]14 We report here results on the initial zero-order kinetic phase since the present study aims to answer the question whether r evap (initial) is an accurate descriptor of the volatility of liquid mixtures in place of r evap (AcOBu = 1) values commonly missing in SDS. A qualitative interpretation of the rate data is offered for the 15 mixtures included in this study.…”

Advances in Fire Debris Analysis

“…When the casework sample is partially evaporated, it becomes necessary to prepare a comparable reference sample. McIlroy and coworkers address the need to prepare accurately evaporated samples by numerically estimating the chromatographic profile of a partially evaporated ignitable liquid for comparison with the residue contribution of a casework sample [6].…”