An analytical method using liquid chromatography with tandem mass spectrometry (LC–MS/MS) was established and validated for screening 425 drugs and poisons in dried blood spots (DBSs).
Blood (20 μL) was spotted on Whatman FTA™ classic card to prepare DBS sample, then extracted with 150 μL methanol and analyzed by LC–MS/MS using a multiple reaction monitoring method.
The limit of detection of the compounds were 0.1–10 ng/mL. The values for recovery and matrix effect were 40.3–114.9% and 40.2–118.4%, respectively. This method was successfully applied to DBS samples from 105 humans suspected of drug poisoning, which was stored for 3–5 years at room temperature. Thirty-three kinds of drugs, including benzodiazepines, antipsychotics, antidepressants, antipyretic analgesics, non-steroidal anti-inflammatory drugs, antibiotics, antiepileptic drugs, new psychoactive drugs were confirmed in 102 cases, while no compound was detected in the other 3 cases. Estazolam, a benzodiazepine widely used in clinical practice as a sedative, hypnotic, and anti-anxiety drug, was the most frequently detected substance, occurring in 34.2% of the cases.
Most drugs in DBS could still be detected after storage for 3–5 years, but ambroxol, zopiclone, carbofuran, chlorpyrifos, and valproic acid were not detectable after 3–5 years of storage at room temperature. The components measured in DBS were consistent with those measured in whole blood at the collection time, thereby confirming that DBS samples have the advantage of stable storage at room temperature.