Evaluation of liquid chromatography–negative ion electrospray mass spectrometry for the determination of selected resin acids in river water

A liquid chromatography–negative ion electrospray mass spectrometric (LC–ESI-MS) method was evaluated for detection of four prevalent softwood-derived resin acids in natural water. Method detection limits based on a signal-to-noise ratio of 3:1 in river water samples of 0.40, 0.40, 0.30 and 0.25 μg l−1 for abietic, dehydroabietic, isopimaric and pimaric acids, respectively, are comparable or lower than reported GC methods. Unlike the majority of GC methods, however, the three structural resin acid isomers (abietic, isopimaric and pimaric acids) do not separate sufficiently under the various LC conditions evaluated in this work. Therefore, LC–ESI-MS may not be suitable for instances where measurement of individual isomeric resin acids is required. However, the method is suitable for trace analysis of resin acids in natural waters where isomeric speciation is not required.