230
6.4 Optimization of Extraction Parameters
An extraction method can be selective for a specific analyte by monitoring the process parameters like temperature, pressure, flow, or power.
6.4.1 Type of Extraction Solvent
Being applied in the extraction methods as alternatives to conventional solvents,
deep eutectic solvent should have high affinity for the target analytes (Yousefi et al.
2018). They should possess low solubility in supported liquid membrane solvent
and high stability in the lumen of the used membrane in the case of hollow-fiber
liquid-phase microextraction method (Khataei et al. 2018). Extraction process is
affected not only by the type of hydrogen bond donor but also by the proportion of
functional groups. For example, in contrast to the aqueous two-phase system extraction method, Yanhua et al. (2015) declared that hydrogen bonding interactions could
be the main driving force in protein extraction; the OH groups can form hydrogen
bonds with proteins more than the NH 2 groups because the electronegativity of oxygen is greater than that of nitrogen (Yanhua Huang et al. 2015).
6.4.2 Sample to Deep Eutectic Solvent Volume Ratio
(V/V) Optimization
The volume of deep eutectic solvent should be sufficient for the solubilization of the
analytes and for a fast extraction but as low as possible in order to avoid waste and
environmental toxicity and to get a final volume of deep eutectic solvent adequate
for the chromatographic analysis (Khataei et al. 2018; Mohebbi et al. 2018). On the
other hand, a high volume of deep eutectic solvent leads to decreasing the extraction
efficiency, and this is related to the dilution effect when freeze-drying cannot be
performed (Mohebbi et al. 2018).
6.4.3 Matrix Ions
Coexisting ions can enter in competition with the target analytes, thus reducing the
recoveries values, and the extraction efficiency of the method (Karimi et al. 2017).
This parameter reveals the selectivity of the method (Aydin et al. 2018). Salt can act
as an effective dehydrating agent for more hydrophilic analytes, also called saltingout effect, in which the solubility of the analytes in the aqueous solution decreases,
leading to a better extraction and, subsequently, a good-phase separation. However,
L. Nakhle et al.
6.4 Optimization of Extraction Parameters
An extraction method can be selective for a specific analyte by monitoring the process parameters like temperature, pressure, flow, or power.
6.4.1 Type of Extraction Solvent
Being applied in the extraction methods as alternatives to conventional solvents,
deep eutectic solvent should have high affinity for the target analytes (Yousefi et al.
2018). They should possess low solubility in supported liquid membrane solvent
and high stability in the lumen of the used membrane in the case of hollow-fiber
liquid-phase microextraction method (Khataei et al. 2018). Extraction process is
affected not only by the type of hydrogen bond donor but also by the proportion of
functional groups. For example, in contrast to the aqueous two-phase system extraction method, Yanhua et al. (2015) declared that hydrogen bonding interactions could
be the main driving force in protein extraction; the OH groups can form hydrogen
bonds with proteins more than the NH 2 groups because the electronegativity of oxygen is greater than that of nitrogen (Yanhua Huang et al. 2015).
6.4.2 Sample to Deep Eutectic Solvent Volume Ratio
(V/V) Optimization
The volume of deep eutectic solvent should be sufficient for the solubilization of the
analytes and for a fast extraction but as low as possible in order to avoid waste and
environmental toxicity and to get a final volume of deep eutectic solvent adequate
for the chromatographic analysis (Khataei et al. 2018; Mohebbi et al. 2018). On the
other hand, a high volume of deep eutectic solvent leads to decreasing the extraction
efficiency, and this is related to the dilution effect when freeze-drying cannot be
performed (Mohebbi et al. 2018).
6.4.3 Matrix Ions
Coexisting ions can enter in competition with the target analytes, thus reducing the
recoveries values, and the extraction efficiency of the method (Karimi et al. 2017).
This parameter reveals the selectivity of the method (Aydin et al. 2018). Salt can act
as an effective dehydrating agent for more hydrophilic analytes, also called saltingout effect, in which the solubility of the analytes in the aqueous solution decreases,
leading to a better extraction and, subsequently, a good-phase separation. However,
L. Nakhle et al.