Investigation of interferences caused by extraneous chloride in the analysis of inorganic anions with ion chromatography.

A series of experiments were conducted by adding Cl- to the eluent to simulate the contaminated eluent. It was found that the added Cl- would cause the peak response of the anions increase largely. Because of the introduction of the superfluous H+, the total conductivity of each anion band was enhanced, and it was regarded as the increase of the sample anion. In the anions except Cl-, for the low affinities of F- and NO2- for an AS14 column that were close to Cl-, they had the similar variation trends according to the amount of Cl- added to the eluent, and the two anions had the maximal responses when the concentration of Cl- in the eluent was 3 mg.L-1 that was just equal to the content in the sample. As to Br-, NO3-, PO4(3-) and SO4(2-) whose variation trends were the same, all of the peak responses of the anions reached the maximum when the concentration of Cl- in the eluent was 6 mg.L-1. For Cl-, the peak response hardly changed when the amount of Cl- added was less than or equal to the concentration of 3 mg.L-1 in the sample. When concentration of Cl- added in the eluent was more than that in the sample, the peak area of Cl- began to decrease little by little, and the peak was completely covered up when the concentration of Cl- in the eluent was 6 mg.L-1.