Fundamentals and applications of stir bar sorptive dispersive microextraction: A tutorial review

Current trends in sample preparation focus on the miniaturization of the process resulting in what is known as microextraction techniques. Among them stir bar sorptive dispersive microextraction (SBSDME) is one of the most recent techniques. It was presented a few years ago as a hybrid microextraction technique that combines the principles of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE). This novel technique introduces, into the sample solution, a bar-shaped magnet coated with a magnetic (nano)material, which is maintained on the surface by magnetism. Once stirring starts, the competitive action between magnetism and rotational force is exploited. At low rotational speed the (nano)material is retained on the magnet reminding SBSE, whereas at high sufficiently rotational speed the rotational force surpasses magnetism so that the magnetic (nano)material is dispersed into the sample solution as in DSPE. Upon halting rotation, the magnetic field prevails again and attracts the magnetic (nano)material containing the analytes back on the surface of the stirring bar. Finally, the extracted analytes are chemically or thermally desorbed before their measurement with the appropriate analytical instrument. When compared separately to SBSE and DSPE procedures, SBSDME affords, in a single approach, advantages such as lower extraction times than SBSE and easier extraction and post-extraction treatment than DSPE. The main purpose of this tutorial review is to describe the fundamentals and the experimental variables involved in this technique, as well as to compile and critically discuss the published papers concerning analytical methods based on the use of the SBSDME approach, analyzing its evolution and future prospects.