Analysis of linear alkylbenzene sulfonate in environmental water using online SPE LC system coupled with LC-MS/MS

Full scan measurement by flow injection analysis (FIA) was conducted to determine the optimum ionization polarity of target compounds followed by MRM transition optimization. As a consequence, all LASs (C10-C14) were detected as M-H ions at negative polarity and m/z 183 was selected as the product ion of MRM transitions independent of linear carbon chain length.
First, the dilution series of LAS were analyzed without online SPE pretreatment. It was confirmed that the linearity of calibration curve and repeatability for each LAS was excellent and all LAS can be detected from 0.1ppb.
Next, online SPE LC System was constructed. The sample injected from the autosampler was introduced into the pretreatment column. The flow channel was then switched to introduce the analytical mobile phase and the analytical mobile phase guided LAS from the pretreatment column to the analytical column. Pretreatment mobile phase, flow rate and pretreatment time were optimized. In this pretreatment step, LAS was concentrated in the pretreatment column by water-rich mobile phase flow. At the same time, it was expected that some hydrophilic matrices were eliminated. The dilution series of LAS were analyzed and all compounds were detected with excellent linearity. The quantitative analysis of the river water was carried out using this system. The river water sample spiked each LAS (0.1ppb) showed good recovery. By connecting an online SPE LC system to LC-MS/MS, the determination of LAS concentration in environmental water could be automated and simplified.