DETERMINATION OF PHOSPHORUS AND SILICON AS VANADOMOLYBDIC HETEROPOLY COMPLEXES BY NORMAL-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The retention of ion pairs of phosphovanadomolybdic and silicovanadomo lybdic acids with trioctylamine is studied by normal-phase high-perfor mance liquid chromatography on a column packed with Diasorb 130 CN; de tection at 320 nm. In the phosphorus(V)-vanadium(V)-molybdenum(VI) sys tem, where phosphovanadomolybdic and phosphomolybdic acids are formed simultaneously, conditions were selected for the formation of only pho sphovanadomolybdic acid. The main peak in the chromatogram of silicova nadomolybdic acid probably belongs to binary silicomolybdic acid. Cond itions for the separation of silicomolybdic and phosphovanadomolybdic acids are selected; the time of separation is about 20 min. The determ ination limits are 3.2 ng of phosphorus and 10 ng of silicon in a samp le in the column (the lowest detected signal is twice the baseline noi se level). Calibration plots are linear in the ranges 10-80 mu g of ph osphorus and 11.7-93.3 mu g of silicon in 25 mt. The procedure is appl ied to the analysis of samples of steel and tap water.