sample pores making the solvent trapped in pores to heat evenly and rapidly. In
contrast to conventional heating where a certain period of time is needed to heat the
vessel before heat is transferred to the solution, the extraction time is significantly
reduced with MAE because with microwaves the heat is transferred directly to the
solvent (Lopez-Avila 2000; Llompart et al. 2019). In their work, Hailemariam et al.
(2016) compared the efficiency of MAE, Soxhlet extraction and sonication for the
recovery of several classes of pollutants in soils and sediments. The average recovery value for phenolic compounds obtained by MAE was 71% vs. 52% and 57% for
Soxhlet and sonication, respectively. This technique also generated higher
recoveries for most of the organochlorine pesticides investigated, except for
4,4
0 -DDT and dieldrin which were more efficiently recovered by Soxhlet extraction.
Similarly, using MAE resulted in higher recoveries of phthalate esters in comparison
with traditional techniques.
The change in temperature and pressure is another way of increasing speed and
efficiency of conventional extraction methods. Accelerated solvent extraction
(ASE), also referred in the literature as pressurized solvent extraction (PSE),
pressurized liquid extraction (PLE), pressurized fluid extraction (PFE), highpressure solvent extraction (HPSE), high-pressure high-temperature solvent extraction (HPHTSE), pressurized hot solvent extraction (PHWE), subcritical solvent
extraction (SSE) and enhanced solvent extraction (Duarte et al. 2014; SánchezCamargo et al. 2017), has been developed as another alternative to Soxhlet extraction, maceration, percolation or reflux, offering advantages with respect to solvent
consumption, extraction yields, extraction time and automation. First ASE has been
applied for the extraction of environmental hazards from solid matrices. Within a
very short time it was approved by the US Environmental Protection Agency (EPA)
for the extraction of semi-volatiles or base neutral acids (BNAs), PAHs,
polychlorinated biphenyls (PC13s), organochlorine and organophosphorous
pesticides, total petroleum hydrocarbons (TPH) and dioxins from solid samples.
Especially when extracting dioxins, the time with ASE is reduced to 20 min in
comparison to 18 h using Soxhlet (Höfler 2002; Stojić et al. 2018).
ASE combines elevated pressure and temperature with liquid solvents to accelerate the process of extraction which is done in a closed vessel at 50–200
C and
pressure of 1500–2000 psi. Higher temperature increases the extraction kinetics,
while elevated pressure keeps the solvent in liquid phase above its boiling point
(Björklund et al. 2000). The series of different sample size can be processed and the
instrumentation allows extraction in unattended operation (Lopez-Avila 2000). The
extraction can be performed in static and dynamic mode or as a combination of these
two modes, which is often viewed as the best option. The reason is the dynamic ASE
requires a larger volume of solvent than the static one which makes it less suitable for
trace analysis. Static ASE, on the other hand, may lead to incomplete extraction
because of the limited volume of solvent used (Mandal et al. 2015).
When it comes to solid-liquid extraction techniques performed mostly on fluids
and aqueous samples, the most widely accepted one is probably a solid-phase
extraction (SPE) in which a target compound is retained by a chromatographic
stationary phase material packed in disposable cartridges or enmeshed in inert matrix
146
L. Nemček and I. Hagarová
contrast to conventional heating where a certain period of time is needed to heat the
vessel before heat is transferred to the solution, the extraction time is significantly
reduced with MAE because with microwaves the heat is transferred directly to the
solvent (Lopez-Avila 2000; Llompart et al. 2019). In their work, Hailemariam et al.
(2016) compared the efficiency of MAE, Soxhlet extraction and sonication for the
recovery of several classes of pollutants in soils and sediments. The average recovery value for phenolic compounds obtained by MAE was 71% vs. 52% and 57% for
Soxhlet and sonication, respectively. This technique also generated higher
recoveries for most of the organochlorine pesticides investigated, except for
4,4
0 -DDT and dieldrin which were more efficiently recovered by Soxhlet extraction.
Similarly, using MAE resulted in higher recoveries of phthalate esters in comparison
with traditional techniques.
The change in temperature and pressure is another way of increasing speed and
efficiency of conventional extraction methods. Accelerated solvent extraction
(ASE), also referred in the literature as pressurized solvent extraction (PSE),
pressurized liquid extraction (PLE), pressurized fluid extraction (PFE), highpressure solvent extraction (HPSE), high-pressure high-temperature solvent extraction (HPHTSE), pressurized hot solvent extraction (PHWE), subcritical solvent
extraction (SSE) and enhanced solvent extraction (Duarte et al. 2014; SánchezCamargo et al. 2017), has been developed as another alternative to Soxhlet extraction, maceration, percolation or reflux, offering advantages with respect to solvent
consumption, extraction yields, extraction time and automation. First ASE has been
applied for the extraction of environmental hazards from solid matrices. Within a
very short time it was approved by the US Environmental Protection Agency (EPA)
for the extraction of semi-volatiles or base neutral acids (BNAs), PAHs,
polychlorinated biphenyls (PC13s), organochlorine and organophosphorous
pesticides, total petroleum hydrocarbons (TPH) and dioxins from solid samples.
Especially when extracting dioxins, the time with ASE is reduced to 20 min in
comparison to 18 h using Soxhlet (Höfler 2002; Stojić et al. 2018).
ASE combines elevated pressure and temperature with liquid solvents to accelerate the process of extraction which is done in a closed vessel at 50–200
C and
pressure of 1500–2000 psi. Higher temperature increases the extraction kinetics,
while elevated pressure keeps the solvent in liquid phase above its boiling point
(Björklund et al. 2000). The series of different sample size can be processed and the
instrumentation allows extraction in unattended operation (Lopez-Avila 2000). The
extraction can be performed in static and dynamic mode or as a combination of these
two modes, which is often viewed as the best option. The reason is the dynamic ASE
requires a larger volume of solvent than the static one which makes it less suitable for
trace analysis. Static ASE, on the other hand, may lead to incomplete extraction
because of the limited volume of solvent used (Mandal et al. 2015).
When it comes to solid-liquid extraction techniques performed mostly on fluids
and aqueous samples, the most widely accepted one is probably a solid-phase
extraction (SPE) in which a target compound is retained by a chromatographic
stationary phase material packed in disposable cartridges or enmeshed in inert matrix
146
L. Nemček and I. Hagarová