Determination of trace anions in organic solvents.

Ion chromatography along with matrix elimination was used to reliably determine trace levels of anionic contaminants in organic solvents. A 5-ml sample volume was injected directly into the instrument without any sample pretreatment. High-purity deionized water was used to deliver the sample to a preconcentration column, where the anions of interest were retained while the organic matrix was rinsed to waste. A sodium carbonate eluent eluted concentrated anions from the preconcentration column and separated them on a 2-mm pellicular anion-exchange column. The separated anions were detected by suppressed conductivity. This method was used to determine the anionic contaminants of isopropanol, acetone and N-methylpyrrolidone. Method detection limits for chloride, nitrate, sulfate and phosphate were all lower than 1 microg/l.