Effervescence-assisted dispersive micro-solid phase extraction

Extraction techniques are surface dependent processes since their kinetic directly depends on the contact area between the sample and the extractant phase. The dispersion of the extractant (liquid or solid) increases this area improving the extraction efficiency. In this article, the dispersion of the sorbent at the very low milligram level is achieved by effervescence thanks to the in situ generation of carbon dioxide. For this purpose a special tablet containing the effervescence precursors (sodium carbonate as carbon dioxide source and sodium dihydrogen phosphate as proton donor) and the sorbent (OASIS-HLB) is fabricated. All the microextraction process takes place in a 10 mL-glass syringe and the solid, enriched with the extracted analytes, is recovered by filtration. Acetonitrile was selected to elute the retained analytes. The extraction mode is characterized and optimized using the determination of five nitroaromatic compounds in water. The absolute recoveries of the analytes were in the range 61–85% while relative recoveries close to 100% in all cases, which demonstrates the absence of matrix effect on the extraction. These values permit the determination of these analytes at the microgram per liter range with good precision (relative standard deviations lower than 6.1%) using ultra performance liquid chromatography (UPLC) combined with ultraviolet (UV) detection as instrumental technique.

► This article presents a new modality of dispersive micro-solid phase extraction which makes use of an effervescent tablet to disperse the sorbent into the sample.
► The new extraction method is evaluated using the determination of selected nitroaromatic compounds in water as model analytical problem.
► The composition of the tablets as well as other extraction variables are studied in depth in the optimization process.
► The proposed method has been evaluated in terms of linearity, sensitivity and precision. In addition, the absolute and relative recoveries values have been calculated.