New Routes To Elusive Perbromate Unveiled

Synthesis of perbromate, BrO₄^–, has confounded chemists for generations, but recent work shows that the anion can be prepared in a straightforward way from sodium hypobromite (NaOBr) solutions (Inorg. Chem., DOI: 10.1021/ic201329q). Historically, scientists had the most success preparing BrO4– by oxidizing bromate (BrO₃^–) with F₂ or XeF₂. Taking a cue from research on the formation of perchlorate in sodium hypochlorite solutions, a team led by Aleksey N. Pisarenko of Southern Nevada Water Authority investigated whether similar chemistry involving BrO^– could yield BrO₄^–. The researchers found that in a concentrated alkaline NaOBr solution some BrO^– readily decomposed to BrO₃^–. The BrO₃^– then reacted with remaining BrO^– to form BrO₄^–. The team monitored BrO₄^– production by liquid chromatography and tandem mass spectrometry and further discovered that the mass spectrometer’s electrospray ionization process also oxidized BrO₃^– to BrO₄^–. Having relatively easy, safe methods for BrO₄^– synthesis could enable more in-depth studies of the anion’s chemistry and toxicity, as well as BrO₄^– contamination in water disinfected with BrO^– solutions, Pisarenko says.