Preliminary Examination of A New Post-Column Photolysis-Molybdate Reaction Detection System for the Determination of Organophosphorus Compounds By High Performance Liquid Chromatography

High-performance liquid chromatographic detection of UV-chromophore-deficient organophosphorus compounds has been aided by a new post-column photolysis-molybdate procedure. In the new procedure, a methanolic, acidified molybdate reagent is added to the eluent just prior to a photolysis chamber consisting of crocheted Teflon tubing wrapped around a mercury-discharge lamp. Organophosphorus compounds are photolyzed to orthophosphate, which in turn reacts with molybdate to form 12-molybdophosphoric acid (12-MPA). The 12-MPA is reduced photolytically to a molybdenum-blue species that absorbs at 735 nm. Because a photoinitiator (such as peroxydisulfate) is not needed, only one reagent pump is required. A limit of detection of about 10 ppb was indicated for a diphosphonate.