DETECTION SYSTEMS WITH A PHOTODIODE-ARRAY DETECTOR FOR FLOW-INJECTIONAND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF PHOSPHINATE, PHOSPHONATE AND DIPHOSPHONATE

Spectrophotometric detection systems for flow-injection analysis and h igh-performance liquid chromatography were designed for the determinat ion of phosphinate, phosphonate, diphosphonate and isohypophosphate of lower oxidation numbers. Preoxidation and/or hydrolysis of these comp ounds to orthophosphate by peroxodisulphate in an oxidation reactor (1 40-degrees-C) were followed by a colour reaction with a molybdenum(VI) reagent in a second reactor. A photodiode-array detector (200-800 nm) was used to obtain the spectrophotometric characteristics of the colo ured species. An unpredicted absorption spectrum was observed for the reaction product between phosphinate and molybdenum(VI). Both advantag es and disadvantages of using an anion-exchange column (TSKgel SAX) fo r the separation of monomers and dimers, including orthophosphate and diphosphate (pyrophosphate), are discussed.