Liquid chromatography-tandem mass spectrometry detection of benzalkonium chloride (BZK) in a forensic autopsy case with survival for 18 days post BZK ingestion

We report a forensic autopsy case of an elderly man who ingested unknown amount of germicidal disinfectant containing 50% benzalkonium chloride (BZK). He survived for 18 days after BZK ingestion and then died because of pneumonia. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was used to detect three BZK compounds (C12-BZK, C14-BZK and C16-BZK) in the blood. Extraction of BZK was carried out according to a modified QuEChERS method. Chromatographic separation was achieved on an ODS column and detection was performed in selected reaction monitoring mode. The accuracy and the precision were acceptable for quantitative analysis in the concentration range of 10-200 ng/mL for the three BZK compounds. BZK was detected in heart and femoral vein blood samples even 18 days after BZK ingestion. Taking into consideration clinical information during 18 days hospitalization and the autopsy findings, the cause of death was attributed to BZK poisoning. Several toxico-kinetic factors regarding absorption and excretion of BZK in the body were also discussed to elucidate the detection of BZK such a long time after ingestion.