Oil-in-water microemulsions (O/W MEs) are obtained spontaneously by mixing two immiscible liquids (water and oil) in the presence of a surfactant. A co-surfactant is also often needed for ME stabilization. The surfactant provides a microstructure with a definite boundary between oil and water phases. O/W MEs are used as mobile phases in a chromatographic mode known as microemulsion liquid chromatography (MELC). One of the main appeals of O/W MEs is the ability to solubilize compounds in a wide range of polarities, from polar to hydrophobic. The solubilizing effect on sample matrices is also noteworthy. The dual behavior of O/W MEs offers unique selectivity and reduced retention times, with equivalent or superior efficiency compared to conventional reversed-phase liquid chromatography, giving rise to successful isocratic separations. The complex nature of MELC mobile phases allows numerous composition options (type and concentration of surfactant, oil and co-surfactant) that lead to good separation performance, when compared to other chromatographic modes. A thorough revision of the main topics concerning MELC, such as nature and properties of O/W MEs, mechanism of retention, selectivity and diverse aspects related to the experimental practice for the determination of drugs in clinical and pharmaceutical samples, is presented.

通过在表面活性剂的存在下混合两种不混溶的液体（水和油），可自发获得水包油型微乳液（O / W ME）。稳定ME经常还需要辅助表面活性剂。表面活性剂提供了在油相和水相之间具有明确边界的微观结构。O / W ME在称为微乳液液相色谱（MELC）的色谱模式下用作流动相。O / W ME的主要吸引力之一是能够溶解从极性到疏水性的各种极性化合物。对样品基质的增溶作用也值得注意。与常规反相液相色谱法相比，O / W ME的双重性能可提供独特的选择性和缩短的保留时间，且具有同等或更高的效率，可成功实现等度分离。与其他色谱模式相比，MELC流动相的复杂性质允许提供多种成分选择（表面活性剂，油和助表面活性剂的类型和浓度），从而导致良好的分离性能。介绍了有关MELC的主要主题的全面修订，例如O / W ME的性质和性质，保留机制，选择性以及与测定临床和药物样品中药物的实验实践相关的各个方面。