Lab-in-syringe-automated dispersive solid phase extraction using magnetite-functionalized HLB sorbent coupled online to HPLC for determination of surface water contaminants

Abstract: We present a simple approach to magnetic dispersive solid phase microextraction and its automation for the enrichment of water contaminants. Supel^TM-Select HLB (Hydrophilic modified styrene polymer) beads were made magnetically susceptible by introducing magnetite nanoparticles into the sorbent. The so-functionalized sorbent was used in a dispersive solid phase extraction methodology that was automated using the Lab-In-Syringe technique.

The methodology followed a previous study on using magnetic nanoparticles but enabling automated exchange of the sorbent, i.e. developing an in-syringe bead injection concept. In short, optimized volumes of sample and bead suspension were aspirated into the syringe void and dispersed by the aid of a magnetic stirring bar placed inside the syringe. By automatic activation and deactivation of magnetic stirring process, the analytes were retained on the dispersed sorbent, which was, when the stirring stopped, captured on the magnetic stirring bar. Afterwards, the sample solution was discarded, and beads were washed in-syringe with water. Thereafter, an optimized eluent was aspirated to strip the analytes from the anew dispersed sorbent.

The extraction system was coupled online to a liquid chromatograph for the determination of model analytes mebendazole, bisphenol A, benzyl 4-hydroxybenzoate, diclofenac, and irgasan. Essential parameters such as extraction time, elution time, sorbent suspension and eluent volume, as well as phase separation time were optimized. Required system elements were produced by 3D printing. Limits of detection ranged from 1.2 µg/L to 6.5 µg/L with < 7 % RSD for all the analytes at 25 µg/L level. The method was linear over a tested range from 5 µg/L to 200 µg/L. The developed method was successfully implemented for the analysis of the chosen contaminants in surface water (lakes and rivers) with recoveries between 87.8 % and 112.5 %.