Directly-coupled-column ultra-fast liquid chromatography with diode array detection method for the rapid quantification of allergenic disperse dyes in water preconcentrated by magnetic solid-phase extraction.

A directly-coupled-column ultra-fast liquid chromatography coupled with diode array detection method for the determination of 12 allergenic disperse dyes in river water at sub-ppb levels has been developed and successfully validated. The analytical method is based on the use of two different reversed-phased columns connected through a two-position switching valve. A baseline separation was achieved by proper selection of stationary phases, mobile phases, and the use of a gradient elution in both dimensions. Furthermore, an easy-to-handle magnetic solid-phase extraction procedure was developed for the preconcentration of 12 allergenic disperse dyes from river water. An enrichment factor of 100 times was obtained. The results showed excellent performance in terms of trueness (76.8-99.0%), precision (intraday: 2.2-8.0%, interday: 3.3-8.2%), and sensitivity (limits of determination, 0.027-1.46 μg/L). Twenty real samples collected from the outfalls in the Yaojiang, Yongjiang and Fenghuajiang estuary were analyzed, and three of the studied compounds were found in one collected sample (12.6 μg/L for disperse blue 7, 11.6 μg/L for disperse blue 106, and 0.22 μg/L for disperse blue 3).