Synthesis of high molar activity ³³P-labeled phosphorous acid

Studies of phosphorus cycling in the ocean have been greatly facilitated by the use of high molar activity ³²P- and ³³P-labeled phosphate (phosphoric acid) in biological incubation assays. Recently, phosphite (phosphorous acid) has been shown to play an important role in the ocean. Here I report the microscale (100 μmol) synthesis of high molar activity ³³P-labeled phosphorous acid. The scheme incorporates a new combination of known synthetic routes, which requires 20 times less radioactivity than existing methods. The economical production of ³³P-phosphorous acid with molar activity > 37 GBq mol^-1 for use in assays is readily achievable with this scheme. (author)