Combination of precipitation preconcentration and chemical amplification of the signal in flow-injection determination of nanogram amounts of phosphorus

Coprecipitation of ion pairs of quadruply charged molybdovanadophosphoric h eteropoly anions and cations of Brilliant Green with the ion pairs of the s ame dye and paramolybdate ions was used for determining nanogram amounts of phosphorus present as orthophosphates. Filtering of the sol through a colu mn with a filter made of fibrous polypropylene provides on-line preconcentr ation of phosphorus, eliminates the effect of collector, and makes it possi ble to elute the concentrate for subsequently measuring the signal in the f low mode. A combination of this technique with chemical amplification of th e analytical signal lowers the limit of detection to 0.05 ng of phosphorus in 2 mL.