4 Extraction Procedures for Pharmaceuticals from Soil
The fate of pharmaceuticals in soil depends strongly on their physico-chemical
properties and soil texture; they might be sorbed on soil particles and its organic
matter content, degraded by soil microbial community, volatilized, or leached to
groundwater [48]. In order to better understand the fate of pharmaceuticals in soil,
accurate and reliable analytical methods are needed as in to identify and quantify
these molecules at low environmental concentrations ranging from a few μg/kg up to
g/kg [48].
Soil is a very complex matrix, and complex interactions between pharmaceuticals
and soil particles and organic content are established. Besides, in solid environmental matrices, pharmaceuticals are present at very low concentrations with a large
number of potentially interfering compounds. Due to this, analytical method development is a challenging task that requires adequate extraction and clean-up procedures. Extraction techniques should be selective and highly effective. For
example, target analytes should be better recovered when co-extracts (matrix impurities) are fewer. Further, they should be fast, easy, and cheap and require minimal
organic solvent use. A following clean-up step is essential in these methods since
soil is very complex, and a co-extracted matrix contaminant is involuntarily
co-extracted (such as humic and fulvic substances), especially for USE, PLE, and
MAE, which they employ energy to extract pharmaceuticals [49]. Moreover, this
step helps in sustaining analytical devices and to improve limits of detection and
quantification as pharmaceuticals are present at low concentrations in soil. Solidphase extraction (SPE) is the most commonly used clean-up technique for the
extraction techniques discussed in this section. Notwithstanding the foregoing, few
studies have omitted this step since it allows the loss of the analytes along with the
removal of matrix interferences. Despite everything, all of those modern analytical
techniques include decreased sample amounts, less solvent consumption, time
saving, high recoveries, good reproducibility, repeatability, and detection limits.
4.1 Assisted Solvent Extraction (ASE)
The selection of the extractants for trace residues from soil is crucial. One advantage
of ASE is the possibility to choose a wide range of solvents. Several extraction
solvents and buffer solutions have been employed to extract pharmaceuticals simultaneously from soil, with varying degrees of target compound recoveries
[50, 51]. Acetonitrile (ACN), methanol (MeOH), hexane, and water are the most
commonly used solvents for the soil and recognized as safe and environmentally
friendly. Among these, the use of water as a solvent represents the most ecological
extraction method and has already been successfully used with recoveries of over
50% [9, 52, 53]. Generally, a mixture of solvents of different polarity is more
successful for the ASE application. This mixture allows to extract the majority of
444
R. Manasfi et al.
The fate of pharmaceuticals in soil depends strongly on their physico-chemical
properties and soil texture; they might be sorbed on soil particles and its organic
matter content, degraded by soil microbial community, volatilized, or leached to
groundwater [48]. In order to better understand the fate of pharmaceuticals in soil,
accurate and reliable analytical methods are needed as in to identify and quantify
these molecules at low environmental concentrations ranging from a few μg/kg up to
g/kg [48].
Soil is a very complex matrix, and complex interactions between pharmaceuticals
and soil particles and organic content are established. Besides, in solid environmental matrices, pharmaceuticals are present at very low concentrations with a large
number of potentially interfering compounds. Due to this, analytical method development is a challenging task that requires adequate extraction and clean-up procedures. Extraction techniques should be selective and highly effective. For
example, target analytes should be better recovered when co-extracts (matrix impurities) are fewer. Further, they should be fast, easy, and cheap and require minimal
organic solvent use. A following clean-up step is essential in these methods since
soil is very complex, and a co-extracted matrix contaminant is involuntarily
co-extracted (such as humic and fulvic substances), especially for USE, PLE, and
MAE, which they employ energy to extract pharmaceuticals [49]. Moreover, this
step helps in sustaining analytical devices and to improve limits of detection and
quantification as pharmaceuticals are present at low concentrations in soil. Solidphase extraction (SPE) is the most commonly used clean-up technique for the
extraction techniques discussed in this section. Notwithstanding the foregoing, few
studies have omitted this step since it allows the loss of the analytes along with the
removal of matrix interferences. Despite everything, all of those modern analytical
techniques include decreased sample amounts, less solvent consumption, time
saving, high recoveries, good reproducibility, repeatability, and detection limits.
4.1 Assisted Solvent Extraction (ASE)
The selection of the extractants for trace residues from soil is crucial. One advantage
of ASE is the possibility to choose a wide range of solvents. Several extraction
solvents and buffer solutions have been employed to extract pharmaceuticals simultaneously from soil, with varying degrees of target compound recoveries
[50, 51]. Acetonitrile (ACN), methanol (MeOH), hexane, and water are the most
commonly used solvents for the soil and recognized as safe and environmentally
friendly. Among these, the use of water as a solvent represents the most ecological
extraction method and has already been successfully used with recoveries of over
50% [9, 52, 53]. Generally, a mixture of solvents of different polarity is more
successful for the ASE application. This mixture allows to extract the majority of
444
R. Manasfi et al.