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薄膜扩散梯度技术(Diffusive gradients in thin films technique,DGT)是近年来应用于自然水体、沉积物和土壤中活性磷原位测定的一种新技术。利用含碱式碳酸镁的聚丙烯酰胺凝胶膜为DGT新结合相,探讨了初始浓度、放置时间、p H值及离子强度对组装后DGT吸附性能的影响。用10 m L 0.25 mol/L H2SO4对结合相进行洗脱,洗脱率为85%±5%。组装后DGT对磷的测定不受溶液p H值(4.10~9.15)和离子强度(0.001~0.05 mol/L)的影响。在温度25℃,p H 7.00,磷初始浓度为2 mg/L时,DGT对磷的最大吸附容量为20.4μg。初始磷浓度为0.001~20 mg/L时,新DGT测定值与磷钼蓝比色法测定值一致。本方法对磷的检出限为102.4 ng/L。将碱式碳酸镁-DGT和商品化的Ferrihydrite-DGT应用于合成海水、厦门近岸海水、易海、巢湖水和南淝河中的对比检测,结果表明,碱式碳酸镁-DGT能更准确测定不同水体中磷浓度。
Diffusive gradients in thin films technique (DGT) is a new technique applied to in situ determination of active phosphorus in natural waters, sediments and soils in recent years. The effect of initial concentration, storage time, p H value and ionic strength on the adsorption capacity of DGT was investigated by using polyacrylamide gel film containing Mg (Ⅱ) as the new DGT. The binding phase was eluted with 10 mL of 0.25 mol / L H2SO4 with an elution rate of 85% ± 5%. The determination of phosphorus in the DGT after assembly was not affected by the p H value of the solution (4.10-9.15) and the ionic strength (0.001-0.05 mol / L). The maximum adsorption capacity of phosphorus for DGT was 20.4μg at 25 ℃, p H 7.00 and initial phosphorus concentration 2 mg / L. When the initial phosphorus concentration was 0.001 ~ 20 mg / L, the new DGT was consistent with that determined by phosphomolybdate blue colorimetry. The detection limit of phosphorus in this method is 102.4 ng / L. The application of basic magnesium carbonate-DGT and commercial Ferrihydrite-DGT in the comparison of synthetic seawater, Xiamen coastal seawater, Yihai Lake, Chaohu Lake water and Nanxun River shows that the basic magnesium carbonate-DGT can be more accurately determined Different concentrations of phosphorus in water.