Determination of light carboxylic acids in snow and ice from mountain glaciers

Light carboxylic acids are major chemical species in acidic precipitation, particularly in remote areas. They play a significant part in the acidification of the environment. Because the organic acids relate closely to the biosphere in the source, their records in snow and ice provide insight into the changes of paleoenvironment and biogeochemical cycles of C, H, O and S. However, the trace concentration of the acids plus their susceptibility to contamination and the exclusiveness of an analytical procedure to a specific instrument make the determination difficult. With DX-300 ion chromatography (IC), we developed a method with AS4A-SC as a separator, TAC-2 as a pre-concentrator installed in place of the sample loop, ATC-1 as an impurity trap installed before the injection valve, and ASRS-II as the suppressor that is regenerated in 25 mM H2SO4. Using gradient elution and Na2B4O7 solution as the eluent, the method resolves and quantitates within a single run of 14 min over 10 analytes from F−, CH3COO− to PO42−, SO42− and finally to (COO)22−. The relative errors for the anions are: F−, 2.6%; CH3COO−, 4%; HCOO−, 2%; CH3COCOO2−, 6%; methane sulfonate (MSA), 16.8%; Cl−, 3%; NO2−, 4%; NO3−, 2%; Br−, 4.5%; SO42−, 2%; and (COO)22−, 5.8%.