Hydrophobic ionic liquid containing bis(trifluoromethanesulfonyl)imide, [NTf2]-, anions partially dissolve in aqueous phases. The potential ecotoxicity of [NTf2]- means wastewater streams must be closely monitored to avoid environmental release. A new anion chromatography method is presented, which improves on existing techniques and methods by significantly decreasing analysis time and improving chromatographic peak properties. Subsequently, the limit of detection was lowered to 5 µM (1.4 ppm) and limit of quantification lowered to 30 μM (8.5 ppm), without the use of expensive concentrator columns or mass spectrometers. The chromatographic method employed a Dionex AS20 column designed for trace analysis of perchlorate in drinking water, which is ideal for highly polarizable [NTf2]- ions to be detected with high accuracy in the presence of high salinity samples, such as seawater. The technique is consequently ideal for environmental monitoring or process design of [NTf2]- ionic liquid-based applications.