DGT With New Binding Phase And Its Application For Phosphorus Determination In Eutrophic Water

The research to reliable measurement of phosphorus ion is very important for eutrophication and water pollution control in nature water.Yet normal analytical measurements are need to do pretreatment before analysis because speciments are usually lower concentration,complex component,much interference liabilization in nature environment.The classic pretreatment is not only needing false manipulation,long period and heave work but also poor reproducibility and having more errors.So the new technique that is not required pretreatment is becoming very significant for investigation of environmental analytical chemistry even analytical chemistry.The diffusive gradients in thin films technique(DGT)is based on Fick's first law of diffusion.In recent years,it has been widely used in the monitoring of phosphorus in water,sediment and soil.In this paper,a new type of binding phase-polyacrylamide gel membrane containing lanthanum carbonate and CaAl-LDH were first used.The effects of DGT deployment time,initial phosphorus in solution,pH,ionic strength and temperature on the ability of enriching phosphate ion were studied.Finally,explore its application performance in the actual water.The results are as follows:(1)Polyacrylamide/Lanthanum carbonate was used as the binding phase of DGT.In the environmental conditions of pH=7.00,T=25?,initial phosphorus in solution was 5 ?g/mL,the adsorption capacity of Lanthanum carbonate-DGT was 68.73 ?g of per disc and the effective adsorption maximum capacity was 12.82 ?g of per disc.The eluent was H2SO4(2mol/L,5 mL),and the elution efficiency was 92.35%.The measured results of Lanthanum carbonate-DGT was independent of ionic strength(10-6 mol/L-0.1 mol/L)and pH(3.21-6.90).When the temperature was in the range of 5-35 ?,the measured mass of phosphorus by DGT increased with the increase of temperature.The initial phosphorus in solution was 0.10-5.04 ?g/mL,the measured value of Lanthanum carbonate-DGT and Molybdenum blue colorimetric method were in good agreement.When stored time was in the range of 0.5-10 months,the change of the enrichment ability of DGT was not significant.The detection limit(MDL)was 98.12 ng/L.In this paper,Lanthanum carbonate DGT and conventional Ferrihydrite-DGT were used to monitor the water samples of synthetic freshwater,Lake Yihai and Lake Chaohu.Compared with the results,it can beconcluded that Lanthanum carbonate-DGT can be more accurate used to determine the phosphorus concentration in different water samples.(2)Polyacrylamide/CaAl-LDH was used as the binding phase of DGT.The CaAl-LDH was prepared by the method of ethanol assisted liquid phase coprecipitation.The eluent was NaOH(2 mol/L,5 mL),and the elution efficiency was 76.0%.The actual amount of phosphorus adsorbed by CaAl-LDH-DGT was consistent with that of the formula(pH=7.00,T=25 ?,[P]=5 ?g/mL,t=15min-360min).Good agreement was obtained between the two measurements in the initial P concentration from 0.1 ?g/mL to 5 ?g/mL.The measured results of CaAl-LDH-DGT was independent of pH(3.12-7.79)and ionic strength(10-6 mol/L-0.1 mol/L).When the temperature was in the range of 5-35 ?,the measured mass of phosphorus by DGT increased with the increase of temperature.The method detection limit(MDL)was 81.71 ng/L.Field performance of DGT in synthetic freshwater,Lake Yihai and Lake Chaohu.Compared with the results,it can be concluded that CaAl-LDH-DGT can be more accurate used to determine the phosphorus concentration in different water samples.