232
at higher concentrations, the solution viscosity can significantly increase due to the
salting-in phenomena, leading to a noticeable reduction in the diffusion rate of the
target analytes into the extraction liquid phase, thus reducing the extraction efficiency (Khataei et al. 2018; Moghadam et al. 2018; Mohebbi et al. 2018).
6.4.4 Type of Emulsifier Agent
Some microextraction techniques require a nonmiscibility of the deep eutectic solvent in the aqueous solution, for example, emulsification microextraction. Therefore,
it is important to use an emulsifier agent or an aprotic solvent in order to release the
bonding of water-miscible deep eutectic solvent from the water molecules. This
leads to a self-aggregation of deep eutectic solvent molecules. Many aprotic solvents are used: tetrahydrofuran, acetone, 1,4-dioxane, dichloromethane, and others
(Moghadam et al. 2018).
6.4.5 Temperature
As mentioned earlier, this parameter positively affects the viscosity of deep eutectic
solvent, and therefore, it can affect the diffusivity of analytes to deep eutectic solvent; however, it should be optimized in the extraction of thermolabile analytes in
order to prevent their decomposition (Li et al. 2016). When using sorbents coated by
deep eutectic solvent, increasing the temperature can desorb the deep eutectic solvent molecules from the sorbents, thus diminishing the extraction capacity (Huang
et al. 2015). For the extraction of volatile compounds, temperature is a critical
parameter that should be controlled. At high temperature, they are rapidly volatilized which leads to a higher extraction efficiency (Tang et al. 2014). However,
increasing temperature for the extraction of nonvolatile compounds enhances their
desorption from the matrix and their solubilization in deep eutectic solvent (Qi et al.
2015; Huang et al. 2015). In the case of proteins, attention should be paid to the
temperature for it won’t cause proteins denaturation (Li et al. 2016).
6.4.6 Time
An optimal time should be chosen for the best diffusion of the analytes from the
original sample to the deep eutectic solvent. This parameter should be well controlled especially when having an adsorption/desorption process because in liquidphase microextraction methods, the extraction should reach an equilibrium (Tang
et al. 2014). Also, long extraction time can cause high risk of losing solvents and
formation of air bubbles (Khataei et al. 2018).
L. Nakhle et al.
at higher concentrations, the solution viscosity can significantly increase due to the
salting-in phenomena, leading to a noticeable reduction in the diffusion rate of the
target analytes into the extraction liquid phase, thus reducing the extraction efficiency (Khataei et al. 2018; Moghadam et al. 2018; Mohebbi et al. 2018).
6.4.4 Type of Emulsifier Agent
Some microextraction techniques require a nonmiscibility of the deep eutectic solvent in the aqueous solution, for example, emulsification microextraction. Therefore,
it is important to use an emulsifier agent or an aprotic solvent in order to release the
bonding of water-miscible deep eutectic solvent from the water molecules. This
leads to a self-aggregation of deep eutectic solvent molecules. Many aprotic solvents are used: tetrahydrofuran, acetone, 1,4-dioxane, dichloromethane, and others
(Moghadam et al. 2018).
6.4.5 Temperature
As mentioned earlier, this parameter positively affects the viscosity of deep eutectic
solvent, and therefore, it can affect the diffusivity of analytes to deep eutectic solvent; however, it should be optimized in the extraction of thermolabile analytes in
order to prevent their decomposition (Li et al. 2016). When using sorbents coated by
deep eutectic solvent, increasing the temperature can desorb the deep eutectic solvent molecules from the sorbents, thus diminishing the extraction capacity (Huang
et al. 2015). For the extraction of volatile compounds, temperature is a critical
parameter that should be controlled. At high temperature, they are rapidly volatilized which leads to a higher extraction efficiency (Tang et al. 2014). However,
increasing temperature for the extraction of nonvolatile compounds enhances their
desorption from the matrix and their solubilization in deep eutectic solvent (Qi et al.
2015; Huang et al. 2015). In the case of proteins, attention should be paid to the
temperature for it won’t cause proteins denaturation (Li et al. 2016).
6.4.6 Time
An optimal time should be chosen for the best diffusion of the analytes from the
original sample to the deep eutectic solvent. This parameter should be well controlled especially when having an adsorption/desorption process because in liquidphase microextraction methods, the extraction should reach an equilibrium (Tang
et al. 2014). Also, long extraction time can cause high risk of losing solvents and
formation of air bubbles (Khataei et al. 2018).
L. Nakhle et al.