Determinations of trace anions (µg/L (ppb) to ng/L (ppt)) in ultrapure water are important to the power and the electronics industries to prevent corrosion failures resulting from anionic contamination. Consequently, per the ASTM D 5127 the ASTM International limits ionic contamination to ppt concentrations. However, trace anion determinations can prove to be a challenging analysis. Water samples easily absorb contaminants from the environment providing misleading results. In some cases, the contamination may be higher than the sample’s analyte concentrations.<br/><br/>To increase sensitivity, a large sample volume, 10 mL, was loaded in pull mode into the large loop of the AutoPrep module. The sample was transferred through a carbonate removal device to remove carbonate using purified water from the inline purifier which minimizes environmental contamination. The sample is collected and concentrated on a concentrator column. The ppt concentrated anions elute using a potassium hydroxide gradient on anion-exchange column optimized for trace anion determinations and were detected by suppressed conductivity detection. To generate the calibration curve, a 1000x smaller injection volume,10-µL, is loaded into the AutoPrep module. One to 5 aliquots of the 50 µg/L mixed anion standard are degassed by the carbonate removal device, concentrated and detected as the samples. However the total mass-on-column is 1000x lower for the standard than the sample resulting in a calibration plot from 50 to 250 ng/L anion concentration (1 to 5 aliquots). Additionally the AutoPrep technique allows easier manual preparation of the calibrating standard because it is less impacted by environmental contamination.<br/><br/>In this poster, determinations of anions at ppt concentrations are demonstrated using the Dionex AutoPrep module and the Dionex EWP Electrolytic Water Purifier on the Dionex Integrion HPIC system. This approach increases the sensitivity with detection limits in the single to double digit ng/L, in large part by reducing contamination.

Trace anion determinations using inline calibration and an electrolytic water purifier

253rd National Meeting (2017)

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