Comparison of tissue homogenate analytical results with and without standard addition.

Standard addition (SA) has occasionally been utilized as an analytical tool in forensic toxicology. It is recommended for difficult matrices such as tissue or decomposed specimens in which the accurate quantitation of drug may be problematic. However, the additional preparation time and increased use of specimen may limit its general applicability. In this study, the authors compared SA with direct extraction (DE) and quantitation against a blood calibration curve to assess whether the quantitative results were significantly different. Twenty-two postmortem cases were assayed for drugs such as cocaine and metabolites, opioids, and antidepressants by solid-phase extraction followed by gas chromatography―mass spectrometry operated in the selected ion monitoring mode. A two-tailed, homoscedastic Student's t-test demonstrated that the two sets of data were not statistically different (p = 0.81). In addition, SAs were more likely to demonstrate nonlinearity (r 2 < 0.98).