Determination of phosphorus and silicon as vanadomolybdic heteropoly complexes by normal-phase high-performance liquid chromatography

摘要

The retention of ion pairs of phosphovanadomolybdic and silicovanadomolybdic acids with trioctylamine is studied by normal-phase high-performance liquid chromatography on a column packed with Diasorb 130 CN; detection at 320 nm. In the phosphorus(V)-vanadium(V)-molybdenum{VI) system, where phosphovanadomolybdic and phosphomolybdic acids are formed simultaneously, conditions were selected for the formation of only phosphovanadomolybdic acid. The main peak in the chromatogram of silicovanadomolybdic acid probably belongs to binary silicomolybdic acid. Conditions for the separation of silicomolybdic and phosphovanadomolybdic acids are selected; the time of separation is about 20 min. The determination limits are 3.2 ng of phosphorus and 10 ng of silicon in a sample in the column (the lowest detected signal is twice the baseline noise level). Calibration plots are linear in the ranges 10-80 #mu#g of phosphorus and 11.7-93.3 #mu#g of silicon in 25 mL. The procedure is applied to the analysis of samples of steel and tap water.