How diquat kills: Investigation of the toxicological profiles of diquat and bromide ion concentrations in serum by LC-MS/MS and capillary electrophoresis in a suicide case.

Herbicide poisoning commonly involves both paraquat and diquat (DQ); DQ poisoning alone is less frequently reported, and especially rare in Japan. We present a case of fatal DQ poisoning after attempted suicide by ingesting DQ dibromide, requiring intensive care including hemodialysis (HD). Toxicological profiles of DQ, DQ metabolites, and bromide ion in serum were investigated relative to the course of treatment. Quantitative analyses were carried out by liquid chromatography/tandem mass spectrometry (LC-MS/MS) for DQ and its oxidative metabolites, and by capillary electrophoresis (CE) for bromide (Br-). Quantitated initial serum DQ concentration prior to HD#1 was 75 μg/mL. Following HD#1, DQ concentration dropped to 8.4 μg/mL, but re-elevated about 12 hours later (12 μg/mL). HD#2 lowered the DQ concentration to 1.5 μg/mL but again re-elevated prior to death (2.8 μg/mL). Serum Br- concentration pre-HD#1 was 493 μg/mL and dropped to 27-49 μg/mL after HD treatment. While HD treatment seemed to have reduced the DQ concentration significantly, re-elevation of the serum DQ level suggests that it was a temporary relief not enough to prevent the patient from going into multiple organ failure. Possibility of bromism was also investigated, as the ingested herbicide contained 33% DQ dibromide, thus Br- would have also been absorbed into the body along with DQ.