Analysis of a case involving the seizure of heroin and 4-acetamidophenyl acetate.

The analysis of heroin adulterants is critical for profiling heroin production processes and establishing links between drug-related criminal cases. Acetaminophen (APAP) is a common adulterant in seized heroin, while acetylparacetamol (ACE-APAP) was unexpectedly detected together with diacetylmorphine (HER) and APAP in a brown heroin sample via gas chromatography-mass spectrometry (GC-MS), raising the key question of whether ACE-APAP was an analytical artifact from HER-APAP acetylation under GC-MS conditions or a genuine component of the heroin sample. To address this question, ultra-high-performance liquid chromatography-diode array detection (UHPLC-DAD) and ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) were employed for verification and confirmation: UHPLC-DAD with gradient elution and 210 nm detection wavelength identified APAP and ACE-APAP by their characteristic retention times and UV spectra, and UHPLC-MS/MS (positive ESI, MRM and daughter ion scanning modes) confirmed the presence of specific ion pairs for APAP (m/z 152-93, 110) and ACE-APAP (m/z 194-110, 152) in the seized sample. Combined analyses definitively demonstrated that ACE-APAP was a genuine raw material component of the heroin, rather than an artifact formed by acetylation during sample analysis. This finding further infers that APAP was added as a diluent prior to the acetylation step in heroin production-a rare early dilution practice that reveals a distinctive manufacturing process of the drug trafficking group and thus provides novel and valuable forensic insights for criminal investigation and case linkage in drug-related crimes.