citrate buffer, which improves the extraction of some pharmaceuticals such as
sulfonamides, macrolides, and ß-lactams. However, satisfactory recoveries were
obtained using the original unbuffered method [102, 105] and the EN citratebuffered method [101] as reported in Table 5.
5 Extraction Procedures for Pharmaceuticals from Plant
Tissues
The irrigation with reclaimed wastewater represents a source of xenobiotics as
PhACs that are not removed by conventional WWTPs [109–111]. Consequently,
agricultural soils contain a wide range of pharmaceuticals that could be uptaken by
plants through the roots [40, 112]. Vegetables have different types of more or less
branched roots (hairy roots in lettuce, napiform roots of radish, or tuberous roots of
potatoes). However, the type or shape of the root does not influence the radical
absorption which is similar for all the roots [2]. The PhACs dissolved in water arrive
in the rhizosphere, come into contact with the root through the epidermis, and could
enter the vascular system with the absorption of the roots [2]. Depending on several
PhACs, physico-chemical properties such as polarity, ionizable ease, or lipophilicity
could affect the pass through the endodermis and then arriving to the vascular tissue
which is responsible for transporting nutrients to the rest of the plant [113]. Therefore, the PhACs capable of entering the vascular tissue can be translocated from the
root to the aerial tissues such as leaves and fruits. In fact, the main source of PhACs
in the leaves is related to their translocation from the roots to the leaves of the most
polar compounds that move with water [114]. Contrary, non-polar (high K ow )
PhACs are more susceptible to remain in the root compartment commonly in the
cell vacuoles and then bioaccumulating in the root [2]. Moreover, when PhACs are
inside the tissues, they could be metabolized, creating new molecules, usually with
unknown fates and properties [115]. Therefore, in order to be able to detect and
quantify the pharmaceutical products absorbed by plants at low environmental
concentrations, accurate and reliable analysis methods are required to be applied to
the different tissues of which the plants are made [116]. In fact, each fabric presents a
separate challenge to overcome. Plants are characterized by containing large quantities of sugars, waxes, fatty acids, and chlorophyll, which complicates the analysis
due to the difficulty of eliminating these substances. These components of the
matrix, if not carefully removed, can interfere with instrumental analysis by acting
as co-eluents of the target compounds [117, 118]. Taking this into account, the
different extraction processes (QuEChERS, ASE, USE, MAE, etc.) are followed by
a subsequent cleaning phase to obtain clean extracts for accurate detection and
quantification. Ideally, a selective extraction technique allows the recovery of the
compounds of interest, while the interferents remain without being extracted into the
matrix [45, 119, 120]. Extraction methods that require the use of high temperatures
such as ASE or MAE and in some cases due to the USE are more likely to obtain
Development of Methods for the Determination of PhACs in Soil/Earthworm/Crop. . .
449
sulfonamides, macrolides, and ß-lactams. However, satisfactory recoveries were
obtained using the original unbuffered method [102, 105] and the EN citratebuffered method [101] as reported in Table 5.
5 Extraction Procedures for Pharmaceuticals from Plant
Tissues
The irrigation with reclaimed wastewater represents a source of xenobiotics as
PhACs that are not removed by conventional WWTPs [109–111]. Consequently,
agricultural soils contain a wide range of pharmaceuticals that could be uptaken by
plants through the roots [40, 112]. Vegetables have different types of more or less
branched roots (hairy roots in lettuce, napiform roots of radish, or tuberous roots of
potatoes). However, the type or shape of the root does not influence the radical
absorption which is similar for all the roots [2]. The PhACs dissolved in water arrive
in the rhizosphere, come into contact with the root through the epidermis, and could
enter the vascular system with the absorption of the roots [2]. Depending on several
PhACs, physico-chemical properties such as polarity, ionizable ease, or lipophilicity
could affect the pass through the endodermis and then arriving to the vascular tissue
which is responsible for transporting nutrients to the rest of the plant [113]. Therefore, the PhACs capable of entering the vascular tissue can be translocated from the
root to the aerial tissues such as leaves and fruits. In fact, the main source of PhACs
in the leaves is related to their translocation from the roots to the leaves of the most
polar compounds that move with water [114]. Contrary, non-polar (high K ow )
PhACs are more susceptible to remain in the root compartment commonly in the
cell vacuoles and then bioaccumulating in the root [2]. Moreover, when PhACs are
inside the tissues, they could be metabolized, creating new molecules, usually with
unknown fates and properties [115]. Therefore, in order to be able to detect and
quantify the pharmaceutical products absorbed by plants at low environmental
concentrations, accurate and reliable analysis methods are required to be applied to
the different tissues of which the plants are made [116]. In fact, each fabric presents a
separate challenge to overcome. Plants are characterized by containing large quantities of sugars, waxes, fatty acids, and chlorophyll, which complicates the analysis
due to the difficulty of eliminating these substances. These components of the
matrix, if not carefully removed, can interfere with instrumental analysis by acting
as co-eluents of the target compounds [117, 118]. Taking this into account, the
different extraction processes (QuEChERS, ASE, USE, MAE, etc.) are followed by
a subsequent cleaning phase to obtain clean extracts for accurate detection and
quantification. Ideally, a selective extraction technique allows the recovery of the
compounds of interest, while the interferents remain without being extracted into the
matrix [45, 119, 120]. Extraction methods that require the use of high temperatures
such as ASE or MAE and in some cases due to the USE are more likely to obtain
Development of Methods for the Determination of PhACs in Soil/Earthworm/Crop. . .
449