performance especially for the acidic compounds which are more sensitive to the pH
[44, 112, 135].
Up to 16 studies have been reported to employ USE in order to extract PhACs
from plant matrices (Table 6). The versatility and applicability of USE have been
widely demonstrated on about 20 different vegetable matrices with good results.
Lettuce, radish, and tomato were the most studied matrices [31, 41, 44, 112, 120,
133, 134, 136, 137].
The most interesting compounds studied were antibiotics, benzodiazepines, and
nonsteroidal anti-inflammatory drugs (NSAIDs), such as carbamazepine, diazepam,
sulfamethoxazole, sulfamethazine, trimethoprim, etc.
5.3 QuEChERS (Quick, Easy, Cheap, Effective, Rugged,
Safe)
The QuEChERS method is the most used extraction technique for pharmaceutical
residues. In fact, more than 25 studies using QuEChERS for drugs in plant tissues are
reported in Table 6. The extraction of QuEChERS mainly depends on the selection
of three phases: the solvent, the salts required, and the cleaning phase. Many of the
reported studies are based on more or less important modifications of the original
procedure developed by Anastassiades et al. for the determination of pesticides in
food [19]. In the original method, ACN was the solvent selected for its ability to
extract non-polar and relatively polar compounds and has the ability to leave
lipophilic substances without being extracted [138]. In addition, ACN mixes easily
with water allowing the penetration of the organic solvent into the matrix
[138]. Reports have shown that ACN is by far the most widely used solvent,
sometimes buffered with acidifying compounds to improve extraction efficiency.
Different solvents such as H 2 O or MeOH have also been used less frequently but
also providing good extraction recoveries. The original method requires a sample
weight of 10 g of fresh material with a water content greater than 80%. Sometimes,
for dry, dehydrated, or fat-rich samples, water is added up to the minimum quantity
required for the extraction [35, 139, 140]. Acidification of the organic solution,
majorly with acetic acid or formic acid, has shown to improve the recoveries of
compounds susceptible to pH [121, 141]. The main difference with the other
extraction methods consists in the use of salts which force the analytes to pass
from the aqueous phase to the organic phase, known as the salting out process
[142]. Taking as a reference the original method, MgSO 4 with NaCl were the salts
employed [19]. MgSO 4 is used for several reasons. In fact, it helps in the separation
between phases (ACN/water) by saturation and is also used for its drying capacity.
Finally, the drying process involves an exothermic process with consequent release
of heat which leads to a better extraction of the non-polar compounds [138]. On the
other hand, the main purpose of NaCl consists of the reduction of polar interferences
and co-extractives coming from the plant [138]. Three main types of salts are used in
464
R. Manasfi et al.
[44, 112, 135].
Up to 16 studies have been reported to employ USE in order to extract PhACs
from plant matrices (Table 6). The versatility and applicability of USE have been
widely demonstrated on about 20 different vegetable matrices with good results.
Lettuce, radish, and tomato were the most studied matrices [31, 41, 44, 112, 120,
133, 134, 136, 137].
The most interesting compounds studied were antibiotics, benzodiazepines, and
nonsteroidal anti-inflammatory drugs (NSAIDs), such as carbamazepine, diazepam,
sulfamethoxazole, sulfamethazine, trimethoprim, etc.
5.3 QuEChERS (Quick, Easy, Cheap, Effective, Rugged,
Safe)
The QuEChERS method is the most used extraction technique for pharmaceutical
residues. In fact, more than 25 studies using QuEChERS for drugs in plant tissues are
reported in Table 6. The extraction of QuEChERS mainly depends on the selection
of three phases: the solvent, the salts required, and the cleaning phase. Many of the
reported studies are based on more or less important modifications of the original
procedure developed by Anastassiades et al. for the determination of pesticides in
food [19]. In the original method, ACN was the solvent selected for its ability to
extract non-polar and relatively polar compounds and has the ability to leave
lipophilic substances without being extracted [138]. In addition, ACN mixes easily
with water allowing the penetration of the organic solvent into the matrix
[138]. Reports have shown that ACN is by far the most widely used solvent,
sometimes buffered with acidifying compounds to improve extraction efficiency.
Different solvents such as H 2 O or MeOH have also been used less frequently but
also providing good extraction recoveries. The original method requires a sample
weight of 10 g of fresh material with a water content greater than 80%. Sometimes,
for dry, dehydrated, or fat-rich samples, water is added up to the minimum quantity
required for the extraction [35, 139, 140]. Acidification of the organic solution,
majorly with acetic acid or formic acid, has shown to improve the recoveries of
compounds susceptible to pH [121, 141]. The main difference with the other
extraction methods consists in the use of salts which force the analytes to pass
from the aqueous phase to the organic phase, known as the salting out process
[142]. Taking as a reference the original method, MgSO 4 with NaCl were the salts
employed [19]. MgSO 4 is used for several reasons. In fact, it helps in the separation
between phases (ACN/water) by saturation and is also used for its drying capacity.
Finally, the drying process involves an exothermic process with consequent release
of heat which leads to a better extraction of the non-polar compounds [138]. On the
other hand, the main purpose of NaCl consists of the reduction of polar interferences
and co-extractives coming from the plant [138]. Three main types of salts are used in
464
R. Manasfi et al.