| Abstract: | Abstract The method is based on the polarographic behavior of 12-tungstophosphoric acid in nonaqueous media at the DME utilizing the differential pulse polarographic technique. In this procedure, orthophosphate is converted to 12-tungstophosphoric acid H3 PW 12 O 40 by reacting with tungstate under acidic conditions and at 100°C. The H3 PW 12 O 40 is extracted into 1-pentanol and its polarographic measurement is made in 1-pentanol-ethanoi mixture containing sodium perchlorate as supporting electrolyte. The differential pulse polarogram of H3 PW 12 O 40 in this solution shows three peaks between 0.00 and -0.90 V vs. Ag/ AgCl. The most cathodic peak at -0.78 V exhibited the highest peak current value and was used for the analytical measurement. A linear calibration graph in the range 0.10 - 5.00 pg/ml P in the final solution was obtained. The method has a relative standard deviation of 0.90% at the 4 pg/ml P level and 1.32% at the 1 μg/ml P level in the final solution. Arsenate, borate and silicate do not interfere. |
