Comments on: Uncertainty of Blood Alcohol Concentration (BAC) Results as Related to Instrumental Conditions: Optimization and Robustness of BAC Analysis Headspace Parameters. Chromatography 2015, 2, 691–708

Abstract

The 2015 publication of original research by Boswell and Dorman [1], Uncertainty of Blood Alcohol Concentration (BAC) Results as Related to Instrumental Conditions: Optimization and Robustness of BAC Analysis Headspace Parameters described an evaluation of the effect of modifying headspace parameters on ethanol analysis by gas chromatography with dual flame ionization detection (GC-FID). The data reported may be useful when developing a new method for ethanol analysis, however there are several suggestions and considerations that should be made regarding implementing the protocol, as described in the paper.1. The method was described as an optimized analytical process for the determination of blood ethanol concentration (BAC) although human blood samples, which are primarily the type of forensic evidence received for BAC testing, were not part of the experimental design and since no matrix effect evaluation was completed, this method could not be used on casework evidence in an accredited laboratory.2. Insufficient empirical data is provided to appropriately estimate the uncertainty of measurement (UOM) for a quantitative measurement, although the authors referenced a publication in which an appropriate approach is described [2]. Historically, an UOM was not routinely calculated and/or reported in a forensic toxicology laboratory as stated by the authors, but currently many laboratories have been accredited to the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) 17025 and American Society of Crime Laboratory Directors/Laboratory Accreditation Board (ASCLD/LAB) Supplemental standards which require an estimation of the UOM to be performed for BAC determinations and weight measurements near statutory limits [3]. Providing an UOM based on data supporting the method described would be a valuable contribution for the laboratories considering implementation on casework evidence.3. The authors rightfully conclude that "chromatographic resolution and peak shape are vital in determining peak area for quantification of blood alcohol determination". An explanation why chromatographic resolution for one of the internal standards used, t-butanol, was not achieved would be insightful for the reader. The resolution mixture presented in Figure 2 did not include t-butanol. Examination of the caption of Figure 2 reveals that t-butanol would coelute with acetone on the DB-ALC1 column and with acetonitrile on the DB-ALC2 column. Coelution of the internal standard with acetone is of considerable concern for a BAC method as acetone is frequently found in human blood samples [4,5], and if present would interfere with the internal standard quantitation of ethanol by causing a falsely low concentration.4. In 2013, The Scientific Working Group for Forensic Toxicology (SWGTOX) published standard practices for method validation in forensic toxicology [6]. In order for the method described to be in compliance with the 2013 validation guidelines and for the method to be fit-for-use in whole bl...

Reply to Comment on “Uncertainty of Blood Alcohol Concentration (BAC) Results as Related to Instrumental Conditions: Optimization and Robustness of BAC Analysis Headspace Parameters”. Chromatography 2015, 2, 691–708

“…This paper was evaluating two of the more impactful parameters: vial pressurization and vial incubation temperature. In reading the comments authored by Tiscione [2] regarding our publication we have the following additional comments.…”