Quantitative Analytical Methods

Abstract

Quantitative analytical methods allow the forensic toxicologist to derive the amount of a xenobiotic present in a biological specimen. Quantitative analyses are frequently requested and commonplace in today’s forensic toxicology laboratory. With proper development and implementation, numerous analytical methodologies are well-suited to provide quantitative data. These analytical techniques include but are not limited to gas chromatography (GC) and liquid chromatography (LC), which provide the chromatographic separation of chemical compounds, and are combined with numerous detector technologies including, most commonly, mass spectrometry (MS) for non-volatile compounds and flame ionization detectors (FID) for volatile organic compounds. Current mass spectrometry technology may allow for the quantitation of compounds without, in some cases, achieving chromatographic baseline resolution, which was once considered crucial. Rigorous method validation provides the analyst with confidence in the methodology being utilized to generate quantitative results, while on a day-to-day basis, the use of proper quality control ensures the accuracy of the obtained quantitative result. Although quantitative results are generated by instrument software following the analysis of a series of samples, it is critical that the analyst within a laboratory understand how those results are obtained and have the ability to convey that understanding in court if required.