In MAE applied to plant matrices, the choice of solvent and the nature of the matrix significantly influence the extraction efficiency. Typically, solvents with high dielec­tric constants are preferred as they absorb microwave energy effectively. The application of microwave energy can lead to enhanced recovery of secondary metabolites and aroma compounds from plant tissues. This is attrib­uted to the disruption of cell structures, facilitated by the rapid heating and vaporization of water within the cells, which in turn aids in the release of target compounds into the surrounding solvent. Structural changes in plant tis­sues due to microwave treatment have been observed through various microscopy techniques, demonstrating the effectiveness of MAE in promoting cell disruption and facilitating solvent penetration for extraction [81–83].

Tswett was a pioneer in the early twentieth century who developed column adsorption chromatography, primarily for the purpose of separating plant pigments. The initial exposition of his findings took place during a speech in 1903 entitled “On a novel classification of adsorption phe­nomena and their utilization in biochemical analysis” [125]. In a 1906 publication, he expanded upon the notion of chromatography and introduced the term “chromato­gram” while conducting experiments with various eluents [125]. By the late 1930s, column adsorption chromatogra­phy, which is currently referred to as normal phase chro­matography, gained significant popularity as a technology for effectively separating plant extracts and natural com­pounds. Although Tswett’s approach was useful, it had drawbacks such as limited resolution and difficulties with substances that are soluble in water. In 1941, Martin and his colleagues made noteworthy progress by introducing partition chromatography, which is often referred to as liquid–liquid chromatography (LLC). This method inte­grated Tswett’s chromatography based on adsorption with countercurrent solvent extraction, resulting in enhanced separations. Martin and Synge were awarded the Nobel Prize in Chemistry in 1952 for their ground-breaking research on partition chromatography [126]. In 1944, they also pioneered the use of paper chromatography, which was the first microanalytical technique [127]. Nevertheless, the relatively sluggish movement of substances in paper chromatography prompted the emergence of thin-layer chromatography (TLC), which entailed the deposition of thin layers of adsorbent material onto glass plates [128].

As a result of the varying mobilities of compounds, they leave the column at different times, leading to distinct retention times (R

Solvent mixtures can be employed for elution in order to modify the polarity of the mobile phase. Isocratic elution refers to the condition when the content of the solvent remains constant. Gradient elution refers to the practice of changing the content of the solvent mixture during elu­tion. The diffusion of molecules in a solvent is contingent upon the qualities of both the molecules and the solvent, particularly their size and viscosity. Although the size of molecules cannot be manipulated, it is essential to use sol­vents with reduced viscosity. It is better to choose methanol over ethanol since it has a lower viscosity of 0.54 cP at 25 °C [158].