Analytical Methods for Environmental Contaminants of Emerging Concern. Группа авторов

extraction of a large number of pesticides within a wide polarity range in only one step [94]. Two different extraction solvents, dichloromethane:acetone (1 : 1, v/v) and acetonitrile:water (2 : 1, v/v), were used for the determination of triazines, phenylureas and phenoxy acid pesticides [95]. Fungicides and insecticides were also extracted using PLE, applying two extraction solvents, methanol:acetonitrile (70 : 30, v/v) and methanol:acetonitrile:formic acid (65 : 30:5, v/v), obtaining recoveries from 57% to 136% [96].

The QuEChERS approach has been widely used to extract pesticides from soils [3] and several modifications were carried out to improve sample extraction. One of them was matrix hydration, which consisted of the addition of water before solvent addition [97]. This approach was used for the extraction of pydiflumetofen enantiomers, obtaining recoveries between 84–103% or for the determination of afidopyropen and its metabolite residues in a cotton field with acceptable recoveries (85–100%) [98]. Another modification was the acidification of the solvent to improve the extraction of target analytes. For instance, acetonitrile, acidified with 2.5% formic acid, provided acceptable recoveries (70–120%) for the simultaneous monitoring of 218 pesticide residues in clay loam soil [99]. The clean-up step was not commonly used in soil samples and only a few studies employed dispersive solid phase extraction (d-SPE). The sorbents and salts commonly used were primary secondary amine (PSA) and anhydrous magnesium sulphate (MgSO₄) [98, 100]. Other sorbents, such as C18, were also used in combination with PSA [61] or with MgSO₄ [97].

      Finally, SPE, using OASIS HLB cartridges, was also applied to concentrate the extract before chromatographic analysis [93].

Tissue analysis is more challenging than water or soil analysis due to the complexity of those matrices. Thus, for the extraction of pesticides from biota, different extraction techniques can be applied such as SPME [40], PLE, SPE, ultrasonic-assisted extraction, dispersive liquid-liquid extraction and SBSE [101], adding a freezing-lipid filtration in fatty materials. Other procedures such as QuEChERS have been widely used in the last few years, using in the clean-up step based on d-SPE a mixture of sorbents that includes MgSO₄, PSA, C18 and graphitized carbon black (GCB) [46, 47, 49], as indicated in Table 1.3.

Finally, pesticides are usually extracted from air using active or passive samplers (see Table 1.4). The active ones are mainly based on SPE by pumping high volumes of air through different sorbents such as Tenax TA, Carbotrap or polyurethane foam filter (PUF) [54, 102]. Passive samplers are based on diffusion through a well-defined barrier or membrane (e.g. Radiello) PUF disks or semipermeable membrane devices [33]. Then compounds are desorbed from the passive sampler using Soxhlet extraction [55, 103], microwave-assisted extraction [104], PLE [105] or ultrasound-assisted extraction [33]. In this sense, different solvents can be used for the extraction of pesticides from filters or membranes, such as ethyl acetate [57], acetone or petroleum ether [55]. Additionally, miniaturized methods can also be applied, and, for instance, pesticides were extracted from PM2.5 using a miniaturized device with 500 µL of 18% acetonitrile in dichloromethane followed by sonication and injection into GC-MS [58].

Table 1.3 Overview of analytical methods applied to determine pesticides in biota.^a

Pesticides	Matrix	Extraction technique	Determination technique	Recovery (%)	LOQ (ng g−1)	Reference
50	Fish	QuEChERS	LC-QqQ	—	—	[49]
50 (TPs)	Fish	QuEChERS Clean-up: d-SPE (MgSO4 + C18 + active coal)	LC-QqQ	58−140	0.90−11.25	[46]
40 (TPs)	Fish	QuEChERS Clean-up: d-SPE (MgSO4 + C18 + PSA + activated charcoal)	LC-QqQ	58−145	0.01−1^b	[47]
50	Fish	QuEChERS Clean-up: d-SPE (MgSO4 + C18 + PSA + active coal)	LC-QqQ	58−140	0.90−11.25^1	[48]
10 OCPs	Fish	PLE: dichloromethane:hexane 1 : 1 v/v. Clean-up: silica gel & basic alumina	GC-Q-MS	50−110	0.0055−0.0300 dw ^b	[105]
OCPs	Several species	Soxhlet: Hexane:acetone 3 : 1 v/v. Clean-up: acid silica	GC-Q-MS	—	1−4	[103]
16 OCPs	Soil & microorganisms	Soxhlet: Hexane:dichloromethane 3 : 2 v/v. Clean-up: GPC Hexane:dichloromethane 1 : 1 v/v	GC-ECD	—	—	[45]

      ^aAbbreviations: d-SPE: Dispersive solid phase extraction; dw: dry weight; ECD: Electron capture detector; GPC: Gel permeation chromatography; LC: Liquid chromatography; MS: Mass spectrometry; MS/MS: Tandem mass spectrometry; OCPs: Organochlorine pesticides; PLE: Pressurized liquid extraction; PSA: Primary secondary amine; Q: Single quadrupole; QqQ: Triple quadrupole; TPs: Transformation products.

      ^bLimit of detection.

Table 1.4 Overview of analytical methods applied to determine pesticides in air matrices.

Pesticides	Matrix	Extraction technique	Determination technique	Recovery (%)	LOQ (pg m−3)	Reference
20	Indoor air	Passive Sampling (VERAM) MAE: acetone:hexane, 1 :