38
S. Iftekhar et al.
SELEX
Systemic evolution of ligands by exponential enrichment
SPE
Solid-phase extraction
SPME
Solid-phase microextraction
2.1 Introduction
Wastewater and water pollution has emerged as a global problem as a result of
the increased contamination of environmental water and its sources (Kolpin et al.
2002; Matamoros et al. 2012; García-Córcoles et al. 2019; Kumar et al. 2019a, b).
Emerging man-made contaminants that may be present in wastewater and water in
the environment range from pharmaceuticals and personal care products to steroids
and pesticides or herbicides (Kolpin et al. 2002; Nelson and Hage 2006; Matamoros
et al. 2012; García-Córcoles et al. 2019). In some cases, these contaminants occur at
trace or ultra-trace levels in water samples and may be present along with interfering
compounds. Such factors can make it challenging to analyze these contaminants by
current analytical techniques (Nelson and Hage 2006; Huang et al. 2015; GarcíaCórcoles et al. 2019; Singh et al. 2019).
A variety of approaches for sample pretreatment have been employed to analyze
emerging contaminants in wastewater and environmental water samples (GarcíaCórcoles et al. 2019). In liquid–liquid extraction (LLE), the target analyte is transferred from an aqueous sample to an organic liquid phase based on the different
solubilities exhibited by these two liquid phases for the target. This method is wellestablished but is laborious and often requires a large volume of organic solvent (Wu
et al. 2010; García-Córcoles et al. 2019, Deka et al. 2015). Solid-phase extraction
(SPE) is the most widely used pretreatment method for environmental testing (Batt
et al. 2008; Wu et al. 2010; García-Córcoles et al. 2019). In this approach, the sample
is introduced into an SPE cartridge containing a solid sorbent, which is then washed
with solvents to remove interfering compounds and elute the desired target agent for
analysis. However, SPE is still susceptible to interferences and requires moderate
amounts of organic solvents (García-Córcoles et al. 2019). Solid-phase microextraction (SPME) is a variation of SPE that uses a fiber that contains an extracting phase
for compound isolation and introduction into a system for analysis by methods such
as gas chromatography (GC) or liquid chromatography (LC) (Lord and Pawliszyn
2000; Piri-Moghadam et al. 2016). SPME requires less solvent than SPE but is more
expensive and its extraction devices can be fragile (Lord and Pawliszyn 2000; Wu
et al. 2010). Dispersive liquid–liquid microextraction (DLLME) is a method based on
the dispersion of droplets of a liquid extractant within an aqueous sample (GarcíaCórcoles et al. 2019). This can result in rapid extraction; however, DLLME does
require a dispersive solvent and can be difficult to automate (García-Córcoles et al.
2019).
Many analytical methods have also been used to examine emerging contaminants in environmental water samples (García-Córcoles et al. 2019; Kumari et al.
S. Iftekhar et al.
SELEX
Systemic evolution of ligands by exponential enrichment
SPE
Solid-phase extraction
SPME
Solid-phase microextraction
2.1 Introduction
Wastewater and water pollution has emerged as a global problem as a result of
the increased contamination of environmental water and its sources (Kolpin et al.
2002; Matamoros et al. 2012; García-Córcoles et al. 2019; Kumar et al. 2019a, b).
Emerging man-made contaminants that may be present in wastewater and water in
the environment range from pharmaceuticals and personal care products to steroids
and pesticides or herbicides (Kolpin et al. 2002; Nelson and Hage 2006; Matamoros
et al. 2012; García-Córcoles et al. 2019). In some cases, these contaminants occur at
trace or ultra-trace levels in water samples and may be present along with interfering
compounds. Such factors can make it challenging to analyze these contaminants by
current analytical techniques (Nelson and Hage 2006; Huang et al. 2015; GarcíaCórcoles et al. 2019; Singh et al. 2019).
A variety of approaches for sample pretreatment have been employed to analyze
emerging contaminants in wastewater and environmental water samples (GarcíaCórcoles et al. 2019). In liquid–liquid extraction (LLE), the target analyte is transferred from an aqueous sample to an organic liquid phase based on the different
solubilities exhibited by these two liquid phases for the target. This method is wellestablished but is laborious and often requires a large volume of organic solvent (Wu
et al. 2010; García-Córcoles et al. 2019, Deka et al. 2015). Solid-phase extraction
(SPE) is the most widely used pretreatment method for environmental testing (Batt
et al. 2008; Wu et al. 2010; García-Córcoles et al. 2019). In this approach, the sample
is introduced into an SPE cartridge containing a solid sorbent, which is then washed
with solvents to remove interfering compounds and elute the desired target agent for
analysis. However, SPE is still susceptible to interferences and requires moderate
amounts of organic solvents (García-Córcoles et al. 2019). Solid-phase microextraction (SPME) is a variation of SPE that uses a fiber that contains an extracting phase
for compound isolation and introduction into a system for analysis by methods such
as gas chromatography (GC) or liquid chromatography (LC) (Lord and Pawliszyn
2000; Piri-Moghadam et al. 2016). SPME requires less solvent than SPE but is more
expensive and its extraction devices can be fragile (Lord and Pawliszyn 2000; Wu
et al. 2010). Dispersive liquid–liquid microextraction (DLLME) is a method based on
the dispersion of droplets of a liquid extractant within an aqueous sample (GarcíaCórcoles et al. 2019). This can result in rapid extraction; however, DLLME does
require a dispersive solvent and can be difficult to automate (García-Córcoles et al.
2019).
Many analytical methods have also been used to examine emerging contaminants in environmental water samples (García-Córcoles et al. 2019; Kumari et al.