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An aqueous solution containing sodium polyacrylate(PAAS) was used in diffusive gradient in thin-films technique(DGT) to measure DGT-labile Ni2+ concentrations.The DGT devices(PAAS DGT) were validated in four types of solutions,including synthetic river water containing metal ions with complexing EDTA or that without complexing EDTA,natural river water(Ling River,Jinzhou,China) spiked with Ni2+,and an industrial wastewater (Jinzhou,China).Results show that only free metal ions were measured by PAAS DGT,recovery=97.36% in the solutions containing only free metal ions,recovery=49.62% in a solution with metal/EDTA molar ratio of 2:1 and recovery=0 in the solutions with metal/EDTA molar ratios of 1:1 and 1:2.These indicated that the complexes of Ni-EDTA were DGT-inert.The DGT performance in spiked river water(recovery=18.24%) and in industrial wastewater(recovery=12.25%) were investigated,which indicated that the measurement of metals by this DGT device did not include the humic substances complexed fractions of metals.The binding properties of PAAS DGT for Ni2+ were investigated under different conditions of pH value and ionic strength.Conditional stability constants(lgK) of PAAS-Ni complexes were also evaluated.
An aqueous solution containing sodium polyacrylate (PAAS) was used in diffusive gradient in thin-film technique (DGT) to measure DGT-labile Ni2 + concentrations. DGT devices (PAAS DGT) were validated in four types of solutions, including synthetic river water containing metal ions with complexing EDTA or that without complexing EDTA, natural river water (Ling River, Jinzhou, China) spiked with Ni2 +, and an industrial wastewater (Jinzhou, China). Results show that only free metal ions were measured by PAAS DGT, recovery = 97.36% in the solutions containing only free metal ions, recovery = 49.62% in a solution with metal / EDTA molar ratio of 2: 1 and recovery = 0 in the solutions with metal / EDTA molar ratios of 1: 1 and 1: 2 These indicated that the complexes of Ni-EDTA were DGT-inert.The DGT performance in spiked river water (recovery = 18.24%) and in industrial wastewater (recovery = 12.25%) were investigated, which indicates that the measurement of metals by this DGT device did not include the humic substances complexed fractions of metals. The binding properties of PAAS DGT for Ni2 + were investigated under different conditions of pH value and ionic strength. Conditional stability constants (lgK) of PAAS-Ni complexes were also evaluated.