[Recent advances in the development and application of effervescence-assisted microextraction techniques]

Effervescence-assisted microextraction (EAM) is a novel sample pretreatment method based on the reaction of CO₂ and H⁺ donors to generate CO₂ bubbles and promote rapid dispersion of the extractant. During this process, the unique dispersion method increases the contact area between the target molecule and the extraction solvent, and the adsorption/extraction efficiency of the adsorbent/extractant toward the target molecule is also enhanced. The EAM technique is of particular interest due its convenient application, low running costs, reduced solvent consumption, high extraction efficiency, and environmental friendliness. Benefiting from the rapid development of extractants, the evolution and application of the EAM technology is becoming more tuned and diversified. Indeed, the synthesis of new extractants, such as nanomaterials with multi-pore structures, large specific surface areas, and rich active sites, has attracted extensive attention, as has the development of ionic liquids with strong extraction abilities and high selectivities. As a result, the EAM technology has been widely applied to the pretreatment of target compounds in various samples, such as food, plant, biological, and environmental samples. However, since these samples often contain polysaccharides, peptides, proteins, inorganic salts, and other interfering substrates, it is necessary to remove some of these substances prior to extraction by EAM. This is commonly achieved using methods such as vortexing, centrifugation, and dilution, among others. The treated samples can then be extracted using the EAM method prior to detection using high performance liquid chromatography (HPLC), gas chromatography (GC), and atomic absorption spectroscopy (AAS) to detect substances such as heavy metal ions, pesticide residues, endocrine-disrupting compounds (EDCs), and antibiotics. Using effervescence as a novel assisted method for the dispersion of solvents or adsorbents, the concentrations of Pb²⁺, Cd²⁺, Ni²⁺, Cu²⁺, bisphenol, estrogen, and the pyrethyl pesticides have previously been successfully determined. Moreover, many influencing factors have been evaluated during method development, including the composition of the effervescent tablet, the solution pH, the extraction temperature, the type and mass/volume of extractant, the type of eluent, the eluent concentration, the elution time, and the regeneration performance. Generally, the cumbersome single factor optimization and multi-factor optimization methods are also required to determine the optimal experimental conditions. Following determination of the optimal experimental conditions, the EAM method was validated by a series of experimental parameters including the linear range, the correlation coefficient (R²), the enrichment factor (EF), the limit of detection (LOD), and the limit of quantification (LOQ). In addition, the use of this method has been demonstrated in actual sample testing, and the obtained results have compared with those achieved using similar detection systems and methods to ultimately determine the accuracy, feasibility, and superiority of the developed method. In this paper, the construction of an EAM method based on nanomaterials, ionic liquids, and other emerging extractants is reviewed, wherein the preparation method, application range, and comparison of similar extractants were evaluated for the same extraction system. In addition, the current state-of-the-art in relation to EAM research and application when combined with HPLC, cold flame AAS, and other analytical techniques is summarized in terms of the detection of harmful substances in complex matrices. More specifically, the samples evaluated herein include dairy products, honey, beverages, surface water, vegetables, blood, urine, liver, and complex botanicals. Furthermore, issues related to the application of this technology are analyzed, and its future development trend in the field of microextraction is forecasted. Finally, the application prospects of EAM in the analysis of various pollutants and components are proposed to provide reference for monitoring pollutants in food, environmental, and biological samples.