Abstract: A novel ion chromatographic method was developed to directly determine trace anion (Cl~, NO~2, NO~3, SO2~4) in atmosphere absorption solution with incorporation of large volume injection, online sample neutralization, column concentration and online standard addition. After comparing the results in different valve switching times and the chromatograms using different online neutralizing columns, the optimum experimental conditions were established. The application of Inguard H online neutralizing column and Carbonate Removal Device (CRD 200) eliminated the matrices OH~ and carbonate. The improvement of the anion detection limit could be achieved by using large volume injection. The results showed that the detection limits of Cl~, NO~2, NO~3 and SO2~4 were 17.5, 171, 34.7, and 42.4 ng/L, respectively. Online standard addition replaced the preparation of trace anion standard solution and avoided the low recovery of NO~2. The method has the characteristics of automatic operation, good repeatability and high efficiency, and can be applied to the detection of ultra trace anions which are hard to be determined in common ion chromatography.

Key words: atmosphere absorption solution, large volume injection, online neutralization, online standard addition, valve switching, ion chromatography (IC), trace anions