Читать книгу Analytical Methods for Environmental Contaminants of Emerging Concern - Группа авторов - Страница 19

For the monitoring of ultra-trace levels of pesticides in water, extraction and concentration steps are required prior to the analytical determination. Liquid-liquid extraction (LLE) allows for the detection of a large range of non-polar pesticides while requiring minimal instrumentation, being at the same time both a simple and a precise technique. Although less and less, this technique is still used for the extraction of pesticides from water samples prior to gas chromatography (GC) analysis [67, 68]. However, one major drawback is the large solvent volumes, usually dichloromethane, required in LLE. Therefore, solid phase extraction (SPE) has become the most common extraction technique [69]. Indeed, it is the most powerful sampling and enrichment approach for complex mixtures of known and unknown contaminants, and different sorbent phases can be used, allowing for the extraction of a wide range of pesticides with different physico-chemical properties.

As shown in Table 1.1, the polymeric reversed phase sorbent, Oasis HLB, is commonly used for the extraction of pesticides in water samples providing quantitative recoveries in most cases [18, 23, 70–72]. Furthermore, other sorbents have been successfully applied for the analysis of pesticides and their TPs in natural waters, such as a mixture of hydrophilic–lipophilic balance, weak anion and cation exchange sorbents (2 : 1 : 1, w/w/w) [73], and Strata-X reversed in combination with the mixture of Strata-X mixed-mode (AW and CW) and Isolute ENV + [74].

On-site integrated large-volume SPE has also been proven to be a promising tool for the monitoring of pollutants, including pesticides, in water sources [75]. On the other hand, the possibility of using on-line SPE systems allows for minimizing sample manipulation and cross-contaminations as well as improving sample throughput [76]. Hence the development of fully automated methods, based on the combination of on-line SPE and LC-MS, has been given much attention in the last few years, being applied for the monitoring of ca. 100 pesticides in natural and drinking waters [24, 77], as well as 51 pesticides, covering highly polar compounds, in surface and groundwaters [78].

Simple and miniaturized sample preparation techniques have been considered in recent years as optimal alternatives [79]. Among them, solid phase microextraction (SPME) is the most used technique, although the application of QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe)-based protocols [21, 80], stir bar sorptive extraction (SBSE) [77], as well as liquid-phase microextraction (LPME) [81, 82], has also been suitable for the extraction of pesticides from water matrices.

SPME is a simple, sensitive, rapid and solvent-free technique in which the organic compounds are adsorbed/absorbed (depending on fiber coating) directly from the aqueous sample into the fiber and then thermally desorbed at the injection port of the GC, considerably simplifying the analysis procedure. In this sense, the availability of SPME devices in latest GC equipment leads to the complete automatization of the analytical process, allowing for improving data quality, the productivity of staff and instruments, and increasing the sample throughput [83]. This has been demonstrated in recent methodologies involving the on-line combination of SPME and GC coupled to high-resolution mass spectrometry (HRMS) allowing for the determination of priority substances, including pesticides, in surface and wastewaters [84, 85] providing limits of quantification (LOQs) at ng l⁻¹ levels. Novel SPME sorbents, such as magnetic deep eutectic solvent (DES)-based polymeric hydrogel [86] and carbon nanomaterials [87, 88], have been successfully applied for the monitoring of pesticides in different water resources as can be seen in Table 1.1.

On the other hand, vacuum-assisted evaporative concentration has been effective for the monitoring of organic micropollutants [89], including pesticides such as chlorothalonil and TPs (sulphonic acids and phenols) by LC-Orbitrap-MS [90]. However, sometimes these extraction procedures are avoided, and direct injection of water samples, after filtration, can be considered when using LC. In fact, its combination with tandem MS (MS/MS) has allowed for the determination of pesticides at ultra-trace levels in surface and groundwaters [25, 27, 91].

Table 1.1 Overview of analytical methods applied to monitor pesticides in environmental waters.^a

Pesticides	Matrix	Extraction technique	Determination technique	Recovery (%)	LOQ (µg l−1)	Reference
4 OCP and 2 OPPs	Surface water	LLE (dichloromethane)	GC-FID	80–90	0.002	[68]
296 pesticides + 156 pharmaceuticals, 18 consumer products, 10 industrial chemicals and 4 others	Coastal waters	SPE (Oasis HLB and SpePak cartridges)	LC-QTOF-MS	70–130	0.00002–0.300b	[70]
14 pesticides and TPs	Surface waterand drinking water	SPE (Oasis HLB cartridge)	UHPLC-QTrap-MS/MS	85–105	0.01–0.1	[71]
19 acidic herbicides + metabolites	River water	SPE (Oasis HLB cartridge)	LC-QqQ-MS/MS	64–111	0.004–0.022	[72]
6 neonicotinoids and metabolites	Drinking water	SPE (Oasis HLB cartridge)	LC-DAD-QqQ-MS/MS& QTOF-MS	57–120	0.000057–0.000488b	[18]
ca. 500 pesticides and TPs	Surface water and groundwater	SPE (Oasis HLB cartridge)	UHPLC-QTOF-MS	—	—	[23]
8 pesticides + TPs	Surface water	Mix mode SPE:(HLB: WAX: WCX, 2 : 1: 1)	LC-QqQ-MS/MS	43–141	0.00002–0.0056b	[73]
125 pesticides and metabolites + 130 pharmaceuticals and metabolites + 42 antibiotics and metabolites + 63 others	Surface and marine water	SPE (Strata-X and the mixture Strata-X-AW: Strata-X-CW: Isolute ENV + (1 : 1 : 1.5))	LC-LTQ-Orbitrap-MS	83–93	—	[74]
251 contaminants (pesticides, pharmaceuticals or industrial chemicals and their transformation products)	Surface water	Onsite integrative large-volume SPE (HR-X sorbent)	UHPLC-LTQ-Orbitrap MS	60–123	—	[75]
96 including pesticides and TPs	Surface water,groundwater and drinking water	On-line SPE	UHPLC-QqQ-MS/MS	—	0.005–0.025	[24]
51 pesticides	Surface water and groundwater	On-line SPE (Prospekt-2-system)	LC-QqQ-MS/MS	80–125	0.010	[78]
8 pesticides	Surface water and groundwater	QuEChERS (Acetonitrile, MgSO4 and NaCl)	GC-Q-MS	85–103	0.95–13.69	[80]
Cyflumetofen + 2 metabolites	Surface water	QuEChERS (Acetonitrile, MgSO4 and NaCl)	UHPLC-QqQ-MS/MS	79–118	0.7–9.8	[21]
102 pesticides	Surface water and groundwater	SBSE (PDMS) (GC)On-line SPE (LC)	GC-Q-MS (27)UHPLC-QqQ-MS/MS (75)	—	0.015–0.025 (GC)0.005–0.025 (LC)	[77]
10 pesticides	Surface water	HF-LPME	GC-Q-MS	85–115	0.14–1.69	[82]
14 pesticides + 16 PAHs + 26 PCBs + 6 BDEs	Surface water	On-Line SPME (DI, PA fiber)	GC-DFS-HRMS	87–116	0.0001–0.050	[84]
16 pesticides	Surface water, marine water and groundwater	Magnetic SPME with a magnetic DES-based polymeric hydrogel	GC-µECD	61–120	0.006–0.399	[86]
24 pesticides	Surface water	SPME (Novel carbon nanomaterial sorbent)	GC-Q-MS	70–123	0.0007–3.7320	[87]
18 chiral pesticides	Surface water and influent and effluent wastewater	Magnetic SPME (Amino modified multiwalled carbon nanotubes)	LC-QqQ-MS/MS	83–105	0.00035–0.00204	[88]
Pesticides	Matrix	Extraction technique	Determination technique	Recovery (%)	LOQ (µg l−1)	Reference
Chlorothalonil + 6 TPs	Surface water and groundwater	Vacuum-assisted evaporative concentration	LC-Orbitrap-MS	85–110	0.0002–0.010	[90]
215 pesticides and TPs (Method SH2437)30 pesticides(Method LC9045)3 herbicides (glyphosate, AMPA and glufosinate)(Method GLYPH)	Groundwater	SH2437 &: LC9045: Direct injectionGLYPH: derivatization with FMOC prior to on-line SPE	LC-QqQ-MS/MS	78–114	0.001–1.350b0.001–0.028b0.020b	[25]
150 pesticide metabolites	Surface waterand groundwater	Direct injection	LC-QqQ-MS/MS	—	0.003–2.000	[27]
16 polar pesticides + pharmaceuticals	Groundwater	Extraction from passive sampler (POCIS): acetone:methanol	UHPLC-QqQ-MS/MS	42–116	0.00003–0.00135b	[59]

^aAbbreviations: BDEs: Brominated diphenyl ethers; DAD: Diode array detector; DES: Deep eutectic solvent; DFS-HRMS: Magnetic sector high resolution mass spectrometry: DI: Direct injection; FID: Flame ionization detection; FMOC: 9-florenylmethyl-chloroformate; GC: Gas chromatography; HF-LPME: Hollow fiber-liquid phase microextraction; HLB: Hydrophilic-lipophilic balanced; LC: Liquid chromatography; LLE: Liquid-liquid extraction; LOQ: Limit of quantification; LTQ: Linear ion trap; MS: Mass spectrometry; MS/MS: Tandem mass spectrometry; µECD: Micro electron capture detector; OCPs: Organochlorine pesticides; OPPs: Organophosphorus pesticides; PA: Polyacrilate; PAHs: Polycyclic aromatic hydrocarbons; PCBs: Polychlorinated biphenyls; PDMS: Polydimethylsiloxane; POCIS: Polar organic chemical integrative samples; Q: Single quadrupole; QqQ: Triple quadrupole; QTOF: Quadrupole time of flight; QTRAP: Hybrid triple quadrupole-linear ion trap; SBSE: Stir bar sorptive extraction; SPE: Solid phase extraction; SPME: Solid phase microextraction; TPs: Transformation products; UHPLC: Ultra-high-performance liquid chromatography; WAX: Weak anion exchange; WCX: Weak cation exchange.

^bLimit of detection.

In relation to solid samples, such as soils, the most common methods were based on solid-liquid extraction (SLE), pressurized liquid extraction (PLE) and QuEChERS (see Table 1.2). In SLE methods, solvent mixtures such as acetonitrile and water have been widely used. For example, a mixture of water/acetonitrile (10 : 90, v/v) was utilized to monitor pesticide residues in soils from Argentina [62], or a mixture of water/acetonitrile (40 : 60, v/v) was used for the extraction of oxanilic and sulfonic acids metabolites [92]. Hu et al. employed methanol:water (50 : 50, v/v) instead of acetonitrile for the extraction of acetochlor and propisochlor in soils from Beijing (China) [63]. Colazzo et al. tested different solvents and mixtures, such as acetonitrile, methanol, water and methanol/water, choosing methanol as the best option (recoveries ranged from 45 to 90%) to determine pesticide residues in paddy fields and sugar cane from Uruguay [93].

Table 1.2 Overview of analytical methods applied to determine pesticides in soil matrices.^a

Pesticides	Extraction	Determination technique	Recovery (%)	LOQ (µg kg−1)	Reference
Famoxadone and metabolites	SLE: Water/Acetonitrile 1% acetic acid (50 : 50, v/v)	LC-Orbitrap-MS	72–113	20	[28]
OCPs, OPPs, pyrethroids (58)	SLE: Water/Acetonitrile 1% acetic acid. Extraction salts: MgSO4 and sodium acetate Clean-up: MgSO4, PSA & C18	GC-QqQ-MS/MS	69−119	100−5000	[61]
30-multicalss	SLE: Methanol Clean-up: SPE (Oasis HLB)	LC-QTRAP-MS/MS	70−120	1−10	[93]
18-multiclass	SLE: Water/Acetonitrile (1 : 5, v/v)	LC-QqQ-MS/MS	50−120	50	[62]
Fenamidone, propamocarb	SLE: Methanol or Water Clean-up: MgSO4 & PSA	LC-QqQ-MS/MS	77−108	0.4–2	[100]
Oxanilic and sulfonic acid metabolites of acetochlor	SLE: Acetonitrile /Water (60 : 40, v/v)	LC-QqQ-MS/MS	91−120	1−2	[92]
Endosulfan, chlorpyrifos and their metabolites	SLE: Ethyl acetate with a 1 : 5 (w/v) soil-to-solvent ratio	GC-IT-MS	76−95	10−50b	[29]
Acetochlor and Propisochlor	SLE: Methanol/water (1 : 1 v/v) Clean-up: PSA	GC-ECD	80−116	10	[63]
10 OCPs	SLE: Water/Acetonitrile Clean-up: MgSO4	GC-QqQ-MS/MS	70−115	2−40	[106]
10 OCPs and metabolites	QuEChERS. Clean-up: Sulfuric acid and florisil	GC-IRMS	60−100	500	[115]
218	QuEChERS using Acetonitrile 2.5% formic acid. Extraction salts: MgSO4 & sodium acetate	LC-QqQ-MS/MS GC-QqQ-MS/MS	70−120	0.5−20	[99]
Pydiflumetofen enantiomers	QuEChERS Clean-up: MgSO4 & C18	UHPLC-QqQ-MS/MS	84–103	5	[97]
Pyrethroid pesticide metabolite	QuEChERS Clean-up: d-SPE	GC-IT-MS	70−94	13	[64]
32-multiclass	UAE: 40 mL of methanol–water (4 : 1 v/v). 20 minutes	LC-Q-MS	60−110	1.5−5.0	[107]
25-Triazines, phenylureas, phenoxy acid pesticides	PLE: Dichloromethane –acetone (1 : 1, v/v) and Acetonitrile–water (2 : 1, v/v)	LC-QqQ-MS/MS	65−120	0.1−3	[95]
51 Fungicides and insecticides	PLE: Methanol:acetonitrile (70 : 30, v/v) Methanol: Acetonitrile:formic acid (65 : 30:5, v/v)	LC-QqQ-MS/MS	57−136	0.3−8.5	[96]
9 OPCs & PAHs	MAE: Hexane/water (3 : 2 v/v)	GC-QqQ-MS/MS	−	−	[104]
8 Pesticides and metabolites	DLLME	LC-FD	70−120	0.07−80	[114]
8 Chiral pesticides	MSPD-DLLME	LC-QqQ-MS/MS	87−104	0.2−1.5	[65]
5 OPPs	Deep eutectic solvent embedded sponge	LC-UV-Vis	−	−	[113]

^aAbbreviations: DLLE: Dispersive liquid-liquid microextraction; d-SPE: Dispersive solid phase extraction; ECD: Electron capture detector; FD: Fluorescence detection; GC: Gas chromatography; HLB: Hydrophilic-lipophilic balanced; IRMS: Isotope ratio mass spectrometry; IT: Ion trap; LC: Liquid chromatography; MAE: Microwave-assisted extraction; MS: Mass spectrometry; MSPD: Matrix solid phase dispersion; MS/MS: Tandem mass spectrometry; OCPs: Organochlorine pesticides; OPPs: Organophosphorus pesticides; PAHs: Polycyclic aromatic hydrocarbons; PCBs: Polychlorinated biphenyls; PLE: Pressurized liquid extraction; PSA: Primary secondary amine; Q: Single quadrupole; QqQ: Triple quadrupole; QTRAP: Hybrid triple quadrupole-linear ion trap; SLE: Solid-liquid extraction; SPE: solid phase extraction. UAE: Ultrasonic-assisted extraction; UHPLC: Ultra-high-performance liquid chromatography; UV-Vis: Ultraviolet-visible detection.

^bInstrumental method (µg l⁻¹).

The PLE method is based on the use of a solvent that is applied at high pressure and temperature through a solid or semisolid sample (e.g. soils) to effectively extract the analytes, being faster than conventional SLE. The selection of optimum experimental parameters, such as extraction temperature, flush volume and preheat time, can allow the 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	0.01−1b	[47]
50	Fish	QuEChERS Clean-up: d-SPE (MgSO4 + C18 + PSA + active coal)	LC-QqQ	58−140	0.90−11.251	[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 : 1 v/v Clean-up: Alumina-C18 Cartridges	GC-Q-MS	59−174	1−10b	[51]
OCPs	Air samples	PAS: PUF. Soxhlet: acetone	GC-Q-MS	82−126	—	[54]
34 (OCPs & CUPs)	Air samples	PUF. Soxhlet: acetone + petroleum ether. Clean-up: silica column	GC-Q-MS	86−102	0.1−90.7c	[55]
40 & TPs	PM10 (remote, urban and rural areas)	MAE: ethyl acetate	LC-QqQ-MS/MS	—	6.5−32.5	[57]
35	PM10	MAE: Ethyl acetate	UHPLC-Orbitrap	73−116	2.6−75	[56]
13	PM2.5	UAE: 18% of Acetonitrile in dichloromethane	GC-Q-MS	70.2−124 (ethion 31.2–63.0)	7.5−60	[58]
452 (OCPs & CUPs)	Air particles	UAE: dichloromethane	GC-QqQ-MS/MS	—	—	[53]

^aAbbreviations: CUPs: Current-use pesticides; GC: Gas chromatography; LC: Liquid chromatography; MAE: Microwave-assisted extraction; MS: Mass spectrometry; MS/MS: Tandem mass spectrometry; OCPs: Organochlorine pesticides; QqQ: Triple quadrupole; TPs: Transformation products; UAE: Ultrasound-assisted extraction; PAS. Passive air sampler; PUF: Polyurethane foam; UHPLC: Ultra-high-performance liquid chromatography.

^bLimit of detection provided as ng VERAM⁻¹.

^cLimit of detection.