FLOW-INJECTION REAGENT INTRODUCTION BY SUPPORTED LIQUID AND NAFION MEMBRANES - DETERMINATION OF PHOSPHATE

The use of membrane tubing for the introduction of reagents for the de termination of phosphate in waters by flow injection analysis was stud ied. The use of membranes eliminates the need for confluence points in the design of flow injection manifolds. This increases the sensitivit y of the manifold by providing a sufficient reagent excess for the rea ction without diluting the sample. Methods for the introduction of aci d, molybdate and hydrazine were devised for the determination of phosp hate by the Molybdenum Blue method. Several membranes were examined an d Nafion and Accurel (microporous polypropylene) were found to be most useful. Molybdate introduction was achieved using a supported liquid membrane (SLM). Calibration was linear and a detection limit of 12 ppb phosphate (4 ppb phosphorus) was obtained.