Magnetic ionic liquids as non-conventional extraction solvents for the determination of polycyclic aromatic hydrocarbons

Abstract

This work describes the applicability of magnetic ionic liquids (MILs) in the analytical determination of a group of heavy polycyclic aromatic hydrocarbons. Three different MILs, namely, benzyltrioctylammonium bromotrichloroferrate (III) (MIL A), methoxybenzyltrioctylammonium bromotrichloroferrate (III) (MIL B), and 1,12-di(3-benzylbenzimidazolium) dodecane bis[(trifluoromethyl)sulfonyl)]imide bromotrichloroferrate (III) (MIL C), were designed to exhibit hydrophobic properties, and their performance examined in a microextraction method for hydrophobic analytes. The magnet-assisted approach with these MILs was performed in combination with high performance liquid chromatography and fluorescence detection. The study of the extraction performance showed that MIL A was the most suitable solvent for the extraction of polycyclic aromatic hydrocarbons and under optimum conditions the fast extraction step required ∼20 μL of MIL A for 10 mL of aqueous sample, 24 mmol L(-1) NaOH, high ionic strength content of NaCl (25% (w/v)), 500 μL of acetone as dispersive solvent, and 5 min of vortex. The desorption step required the aid of an external magnetic field with a strong NdFeB magnet (the separation requires few seconds), two back-extraction steps for polycyclic aromatic hydrocarbons retained in the MIL droplet with n-hexane, evaporation and reconstitution with acetonitrile. The overall method presented limits of detection down to 5 ng L(-1), relative recoveries ranging from 91.5 to 119%, and inter-day reproducibility values (expressed as relative standard derivation) lower than 16.4% for a spiked level of 0.4 μg L(-1) (n = 9). The method was also applied for the analysis of real samples, including tap water, wastewater, and tea infusion.

High‐throughput microscale extraction using ionic liquids and derivatives: A review

“…In the reported MIL‐DLLME studies, high magnetic susceptibility MILs such as those based on Fe(III) anions (e.g. methyltrioctylammonium tetrachloroferrate or [N 1,8,8,8 + ][FeCl 4 − ] [60] and benzyltrioctylammonium bromotrichloroferrate(III) or [N Bn,8,8,8 + ][FeCl 3 Br − ] [61]) were easily separated by placing the magnet on one side of the extraction vessel. The MIL was immediately attracted by the magnetic field and retained on the walls of the vessel, followed by pouring the matrix sample out.…”

“…The desorption step when using MILs in DLLME has been accomplished using a back‐extraction procedure [61,63] or diluting the MIL with a small volume of organic solvent [60], depending on the compatibility of the MIL with the subsequent analytical technique. The majority of MILs used in sample preparation contained paramagnetic metals as anions [12,13].…”

“…It is important to point out that the majority of online IL‐DLLME applications discussed in this section were focused on the determination of metal species (Table 2) [51–53,67–69,71]. On the contrary, MIL‐DLLME has in general been employed for the determination of triazine herbicides [63], PAHs [50,61,62], phenols [50,60], and other aromatic compounds [50,62], biomolecules such as DNA [64,75], and for the isolation of bacteria [76]. Few applications have employed MIL‐DLLME for metal determination [77].…”

Ionic liquids: solvents and sorbents in sample preparation

“…Trujillo-Rodríguez and coworkers studied the extraction of heavy polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions using three hydrophobic MILs, namely, benzyltrioctylammonium bromotrichloroferrate(III) ([N 8,8 [97]. In this study, the MIL was dispersed using acetone in combination with vortexing and subsequently collected using an external magnet.…”

Headspace single drop microextraction versus dispersive liquid-liquid microextraction using magnetic ionic liquid extraction solvents

“…There are few reported studies using MILs as extraction solvents [26][27][28][29][30][31] ]-based MILs permits direct analysis of the extraction solvent by HPLC-UV. Similar MILs have also been applied in studies employing high ionic strength solutions, demonstrating their stability in the presence of salts [26,27,30]. When MILs are applied as extraction solvents in HS-SDME, the magnetic force maintains the microdroplet on the magnet support throughout the long extraction time as opposed to the droplet being suspended on the tip of a microsyringe needle.…”