Matsubara C, Izumi S, Takamura K, Yoshioka H, Mori Y
Tokyo College of Pharmacy, Japan.
Analyst. 1993 May;118(5):553-6. doi: 10.1039/an9931800553.
A method for concentrating and determining phosphate in natural waters, using poly(N-isopropylacrylamide) (PNIPAAm); a thermally reversible polymer, is described. Poly(N-isopropylacrylamide) is soluble in water below 31 degrees C but shrinks abruptly on heating above 31 degrees C, becoming insoluble. With phase separation of PNIPAAm from aqueous solution at 45 degrees C, a molybdophosphate-Malachite Green aggregate (P-Mo-MG), formed by reaction of a Mo-MG reagent, obtained by mixing ammonium molybdate and Malachite Green, was incorporated in PNIPAAm and the resulting solid stuck to the walls of the reaction vessel. After discarding the supernatant solution by decantation, the P-Mo-MG aggregate was dissolved in a small volume of methylcellosolve together with PNIPAAm. The absorbance (lambda max = 627 nm) was proportional to the concentration of phosphate with an apparent molar absorptivity of 2.6 x 10(4) m2 mol-1. This method makes possible the rapid determination of trace amounts of phosphate in water using simple apparatus. The detection limit was 2 nmol dm-3 of phosphate. The method was successfully applied to the determination of phosphate in natural water samples such as tap water, mineral water and rain water.
描述了一种使用聚（N-异丙基丙烯酰胺）（PNIPAAm）（一种热可逆聚合物）浓缩和测定天然水中磷酸盐的方法。聚（N-异丙基丙烯酰胺）在31摄氏度以下可溶于水，但在加热到31摄氏度以上时会突然收缩，变得不溶。在45摄氏度下PNIPAAm从水溶液中发生相分离时，由钼酸铵和孔雀石绿混合得到的钼酸-孔雀石绿试剂反应形成的磷钼酸-孔雀石绿聚集体（P-Mo-MG）被纳入PNIPAAm中，所得固体附着在反应容器壁上。通过倾析法弃去上清液后，P-Mo-MG聚集体与PNIPAAm一起溶解在少量甲基溶纤剂中。吸光度（λmax = 627 nm）与磷酸盐浓度成正比，表观摩尔吸光系数为2.6×10（4）m2 mol-1。该方法使用简单仪器即可快速测定水中痕量磷酸盐。检测限为2 nmol dm-3磷酸盐。该方法成功应用于自来水、矿泉水和雨水等天然水样中磷酸盐的测定。
