Deep eutectic solvent-based clean-up/vortex-assisted emulsification liquid-liquid microextraction: Application for multi-residue analysis of 16 pesticides in olive oils

Deep Eutectic Solvents Application in Food Analysis

“…Currently, studies on the synthesis and application of HDESs for the extraction of a great variety of analytes from food matrices have expanded rapidly, which has led to an increase in the number of articles published in recent years. As can be seen in Table 2, several HDESs have been used for the extraction of both organic (phthalic acid esters [18,96,99], dyes [97,104,110,117], PAHs [17,85], sterols [98], pesticides [100,105,112,122,124,126,127], herbicides [102], insecticides [125], preservatives [101], pigments [86], antibiotics [87,103,108,114], fluorescent whitening agents [106], vitamins [107], mycotoxins [16], bisphenols [115], perfluoroalkyl substances [120] and terpenes [121]) and inorganic compounds (Co, Cd, Ni, As, V and Pb [109,111,113,116,118,119,123]) from aqueous phases (water [96,113,118,124], soft drinks…”

“…Likewise, procedures such as lyophilization or a previous extraction with an organic solvent (e.g., n-hexane, ACN, MeOH or acetone) were very useful in the treatment of egg yolk, olive oil, chili sauce, honey and some fruit juices, although it may be contradictory with the development of green sample preparation procedures using DESs. As a specific example, a hydrophilic DES has even been used in the treatment of oil samples to reduce the matrix effect [100]. In those cases, in which the matrix is more complex, more laborious procedures previous to the extraction of the compounds of interest are needed.…”

“…In this sense, it is important to highlight that in certain cases, no additional solvents have been necessary to obtain a good dispersion of the HDES into the sample [18,86,[96][97][98]110]. Instead, the DLLME procedure has been assisted in different ways, including the vortex-assisted DLLME [86,97,99,100,104,106], ultrasound-assisted DLLME [16,85,87,101,113,116,123,124], air-assisted [109] and microwave-assisted DLLME [128]. However, other versions have also been used, such as DLLME based on the solidification of the floating organic drop (SFO) [18,115,122,126]; salting out-DLLME-back extraction or salt induced-homogenous liquid-liquid extraction-DLLME, in which a salt is added (e.g., NaCl, (NH 4 ) 2 SO 4 , Na 2 SO 4 or NH 4 Cl) to reduce the solubility of the analytes in water and to increase their distribution coefficients in the organic phase [108,114]; effervescence-assisted DLLME in which an effervescent reaction between a proton donor solvent (acetic acid, which has been previously mixed with HDES in a 3:1 (v/v) ratio) and an effervescent agent (sodium bicarbonate) is produced generating carbon dioxide that facilitates the dispersion of the extraction solvent (HDES, see Figure 2) [117]; or even the combination of DLLME with a previous extraction and clean-up stage, such as the QuEChERS method, in which the extracted supernatant was used as a dispersant in the following DLLME for further purification and preconcentration [112].…”

“…Regarding the final determination of the analytes, different separation and detection techniques have been applied, being LC, both HPLC [17,18,86,87,[96][97][98][99]101,103,104,107,110,112,114,124,125] and UHPLC [115,120], the most extensively used, although some applications of micellar electrokinetic capillary chromatography [108] and GC [85,100,102,105,121,122,126,127] can also be found mainly for non-ionic HDESs, which are characterized by a higher volatility. These separation techniques have been coupled to different detection systems, including UV [18,87,96,97,99,103,107,110,112,124,125], DAD [86,104,114], variable wavelength detectors [98], FD [17,101], MS …”

“…Hydrophobic NADESs have also been used in food analysis, although they are still not very abundant compared to the use of "non-natural HDESs", as shown in Table 2. It is worth highlighting the work of Soltani and co-workers [100], who synthesized a hydrophobic NADES composed of thymol and vanillin (1:1, molar ratio in which a transparent yellow liquid remained). They calculated its solubility in water (0.005%, w/v) and its octanol/water distribution constant (log K OW = 4.30) to verify its hydrophobicity.…”