Preconcentration of aqueous dyes through phase-transfer liquid-phase microextraction with a room-temperature ionic liquid

In this study, we employed the room-temperature ionic liquid [bmim][PF6] as both ion-pair agent and an extractant in the phase-transfer liquid-phase microextraction (PTLPME) of aqueous dyes. In the PTLPME method, a dye solution was added to the extraction solution, comprising a small amount of [bmim][PF6] in a relatively large amount of CH2Cl2, which serves as the disperser solvent to an extraction solution. Following extraction, CH2Cl2 was evaporated from the extractant, resulting in the extracted dyes being concentrated in a small volume of the ionic liquid phase to increase the enrichment factor. The enrichment factors of for the dye Methylene Blue, Neutral Red, and Methyl Red were approximately 500, 550 and 400, respectively; their detection limits were 0.014, 0.43, and 0.02 μg L−1, respectively, with relative standard deviations of 4.72%, 4.20%, and 6.10%, respectively.

Graphical abstract.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We propose a new method of solvent microextraction. ► The new method utilizes the ion-pair behavior of ionic liquid in solvent extraction ► The new method can be employed for the extraction of charged species. ► High enrichment factors can be obtained from the proposed method.