Development and Validation of a Method to Analyze Fentanyl and Its Analogues in Postmortem Blood Samples by LC-MS/MS

The increase in the number of users, hospitalizations and deaths due to overdose of synthetic opioids made the scientific community to treat this problem as "the opioid crisis", justifying the need for the development of analytical strategies to identify and quantify these drugs. Even with the global discussion, there is no Brazilian data regarding opioids consumption, addiction or fatal intoxication cases. The aim of this work was to develop, validate and applied an analytical method based on liquid chromatography-tandem mass spectrometry for determination of fentanyl and seven analogues (acetyl norfentanyl, acetyl fentanyl, thiofentanyl, acrylfentanyl, furanylfentanyl, carfentanil and valerylfentanyl) in postmortem blood samples, to the routine analysis of the Forensic Toxicology Laboratory of Sao Paulo State Police. Linearity was evaluated from 1-500 ng mL-1 (correlation coefficient (r) value (r >= 0.99), 1/x weight linear regression), with limit of quantification of 1 ng mL-1. The method imprecision, bias and matrix effect were lower than 19.7%. No interference or carryover were observed, and extraction yield was greater than 57.7%. Analysis of postmortem blood samples (n = 1,359) showed that fentanyl was the most frequently detected opioid. The developed method proved to be useful for routine analysis of the Forensic Toxicology Laboratory.