Mixed-mode adhesive tape integrated in a syringe plunger: an affordable microextraction device for isolating basic...

Current bioanalytical laboratories must cope with increasing pressure on workflow due to the high number of samples to process and the speed required to generate analytical information. The development of cost-effective extraction procedures capable of processing multiple samples simultaneously can address, or at least mitigate, this enormous challenge. These devices must be affordable and cost-effective, taking into account that disposable units are preferred when biosamples are processed to avoid contamination of operators and carryover effects.

In this work, sorptive plunger-based in-syringe microextraction (SP-ISME) is presented and evaluated for the isolation of seven basic drugs from saliva samples. The extraction device consists of a conventional plastic syringe whose plunger has been coated with mixed-mode cationic exchange (MCX) microparticles using a double-sided adhesive tape as binder. In this case, the sample is aspirated into the syringe, where it is incubated for a defined time under continuous agitation, minimizing handling and allowing multiple samples to be extracted simultaneously. The main variables involved in the SP-ISME (i.e., sample dilution, ionic strength, stirring rate, extraction time, and elution time) have been evaluated in detail. After extraction, the analytes were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry. The analytical performance showed competitive results, yielding limits of quantification of 0.5 μg L^-1 for all analytes, with intra- and inter-day precision lower than 6.1% and 13.2%, respectively, and relative recoveries between 81% and 110%.

The microextraction device is highly versatile, as it can be modified with various types of microparticles, whether commercial or synthesized in the laboratory. Also, its design avoids backpressure, a common issue in some in-syringe devices, because the sample is not flowed through the sorptive phase. The stability of the analytes retained in the sorptive phase after extraction opens the door to on-site applications of this technique.