## 4 Applications of Microextraction Techniques to the Determination of Organic Micropolultants
### Pesticides  
Scientific advances have created the hundreds of synthetic organic compounds used as pesticides. Their physicochemical properties and widespread use in agriculture, antifouling and household products explain their pervasiveness in aquatic environments, including wastewater [56], surface and ground water [57] and seawater from coastal areas [58]. In the field of environmental water policy, annex I of Directive 2008/105/CE includes the maximum allowable concentration of some priority substances. The maximal average annual concentrations authorised for surface water can vary from \(\mathrm{ng\cdot L^{-1}}\) to \(\mathrm{\SIUnitSymbolMicro g\cdot L^{-1}}\). In this case, microextraction techniques are often used to analyse pesticides, as shown in Table 1.  
Solid-phase microextraction (SPME) has been used to extract pesticides. For example, [PERSON] _et al._[59] used this technique with a commercial polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre coupled to a high-performance liquid chromatography (HPLC) system with subsequent detection by inductively coupled plasma-mass spectrometry (ICP-MS) to determine different organotin compounds in fresh- and seawater samples from leisure ports. The optimal method provided limits of detection (LOD) between 6 and 185 \(\mathrm{ng\cdot L^{-1}}\). A high-throughput method based on thin-film solid-phase microextraction (TF-SPME) and liquid chromatography mass spectrometry was developed by [PERSON] _et al._[60] to simultaneously quantify nine benzylic and aliphatic quaternary ammonium compounds in aqueous samples; these compounds are used as disinfectants. TF-SPME has a coating with a higher surface area/volume ratio and is particularly useful when analytes are found in trace amounts, in complex matrices, or in the presence of a binding matrix with low concentrations of free analytes available for extraction. This method was validated according to the Food and Drug Administration (FDA) criteria using river water. The accuracy achieved was near 100%, and the limits of quantification (LOQs) defined by the lowest calibration points ranged from 0.01 to 0.50 \(\mathrm{\SIUnitSymbolMicro g\cdot L^{-1}}\). In-tube solid phase microextraction (IT-SPME) is the most commonly used microextraction technique for assessing organic micropollutants. [PERSON] _et al._[61] used a custom polypyrrole (PPY)-coated capillary to assay polar pesticides (six phenylurea and six carbamates pesticides) in spiked water. The extraction conditions were optimised, particularly the stationary phases; the custom-made capillaries and several commercial capillaries were compared. The LODs of this method for the studied compounds ranged from 0.01 to 1.2 \(\mathrm{\SIUnitSymbolMicro g\cdot L^{-1}}\). [PERSON] _et al._[62] proposed a multiresidue analytical method for the pesticides included in the Water Frame Directive 2000/60/EC (WFD) that combines IT-SPME with a GC TRB-5 capillary column and ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). This method exhibited good linearity over the assayed range and LODs between 0.025 and 2.5 \(\mathrm{\SIUnitSymbolMicro g\cdot L^{-1}}\). This method was applied to several water samples from different sources, demonstrating the on-line enrichment of the analytes with minimal sample manipulations; these compounds were identified, and their concentrations were quantified as low levels in units of parts-per-billion. Stir bar solid extraction (SBSE) was used by [PERSON] _et al._[63] to extract 16 pesticides from surface water samples. This method was validated in spiked surface water samples, and the obtained LODs ranged from 0.01 to 1.0 \(\mathrm{\SIUnitSymbolMicro g\cdot L^{-1}}\). Finally, [PERSON] _et al._[64] optimised an UHPLC-MS/MS method using SBSE to analyse the antimicrobial compounds triclosan and triclocarban in surface and wastewaters. The LODs of the analytical method were 2.5 \(\mathrm{ng\cdot L^{-1}}\) for river water and 5-10 \(\mathrm{ng\cdot L^{-1}}\) for the effluent and influent sewage waters.