International Journal of Medical Laboratory Research (IJMLR)

QUANTIFICATION BIAS IN BLOOD ALCOHOL DETERMINATION BY HEADSPACE GAS CHROMATOGRAPHY

 

Elia Mattarucchi, Carlo Peruzzo, Ramona Consuelo Maio, Ursula Andreotta, Marco Mario Ferrario

 

ABSTRACT: The quantification of blood alcohol concentration is routinely performed in many forensic laboratories by gas chromatography. In this short report, the influence of the matrix miss-match between samples and calibrators (e.g. the use of aqueous standards to quantify blood samples) and the actual efficiencies of different internal standards used to normalise the ethanol signal were considered. Test samples in blood and water were prepared from a certified reference standard of ethanol. The samples were analysed by gas chromatography using n-propanol and t-butanol as internal standards. The collected data provided evidences that a sub-optimal setting of the considered variables can be responsible for a quantification bias up to 15%. These issues are of practical relevance in the medico-legal sector and should be considered during the process of method development.

 

KEY WORDS: blood alcohol concentration, calibrator, internal standard, gas chromatography, bias.

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REFERENCES:

1. Rainey PM. Relation between serum and whole-blood ethanol concentrations. Clin Chem 1993; 39:2288–92.

2. Sklerov JH, Couper FJ. Calculation and verification of blood ethanol measurement uncertainty for headspace gas chromatography. J Anal Toxicol 2011;35:402–10.

3. Scientific Working Group for Forensic Toxicology. SWGTOX standard practices for method validation in forensic toxicology. J Anal Toxicol 2013;37:452–74.

4. Archer M, Vos J, S Visser M. The preparation, assay and certification of aqueous ethanol reference solutions. Accreditation Qual Assur 2007; 12:188–93.

5. Strassnig S, Lankmayr EP. Elimination of matrix effects for static headspace analysis of ethanol. J Chromatogr A 1999;849:629–36.

6. A. Boswell H, Dorman F. 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.

7. Karch S, editor. Forensic Issues in Alcohol Testing. Boca Raton: CRC Press; 2007.30–3.

8. Christmore DS, Kelly RC, Doshier LA. Improved recovery and stability of ethanol in automated headspace analysis. J Forensic Sci 1984;29:1038–44.

9. Schug K. An Indisputable Case of Matrix Effects in Blood Alcohol Determinations. Available at: http://www.chromatographyonline.com/indisputable-case-matrix-effects-blood-alcohol-determinations. Accessed: 16 Oct 2018

10. (2017) Guidelines for institutions equipped with laboratories for the detection of substances of abuse for toxicological-forensic and medico-legal purposes on biological samples taken from living subjects - Rev. N° 5. GTFI guidelines. Available at: http://www.gtfi.it/linee-guida/