Organochlorine pesticides OCPs

Onuska and Terry extracted aldrin, dieldrin, and DDT from soils and sediments using acetonitrile, isooctane, or a mixture of isooctane-acetonitrile (1:1, v/v) and achieved quantitative recoveries using five or seven 30-s irradiations with microwave energy. They also reported that MAE recoveries increases as the moisture content of the soil increases up to 15%. Fish and Revesz used hexane-acetone as extraction solvent and reported that OCP recoveries improved when changing from 1 : 1 hexane-acetone to 2 : 3 hexane-acetone. The latter solvent has a composition similar to the azeotropic vapour in the Sox-hlet extractor.

Lopez-Avila et al. extracted 45 OCPs from freshly spiked and 24-h aged soil samples with hexane-acetone (1:1, v/v). For the freshly spiked soil, 38 compounds had recoveries between 80 and 120%, six compounds had recoveries between 50 and 80%, and the recovery of captafol was above 120%. For the spiked soil samples aged for 24 h, 28 compounds had recoveries between 80 and 120%; 12 compounds had recoveries between 50 and 80%; three compounds including captafol, captan, and dichlone were poorly recovered; and chloroneb and 4,4'-DDT had recoveries above 120%.

When recoveries from freshly spiked soil were compared to those from aged spiked soil, it was found that the recovery of captafol dropped from 122% to 36%, the recovery of captan dropped from 106% to 21%, and the recovery of dichlone dropped from 78% to 10%. Captafol and captan appear to be quite stable upon irradiation of soil/solvent suspensions, but dichlone was found to disappear upon irradiation

Table 3 Selected MAE applications reported in the literature

Analyte

Matrix

Solvent

MAE conditions

Ref.

17 PAHs, 14 phenols, 20 organochlorine, 13 miscellaneous compounds (e.g. chlorinated benzenes nitroaromatic compounds and phthalate esters)

PAHs

PAHs

PAHs

PAHs

PAHs PAHs

PAHs

PAHs

Organochlorine pesticides

16 Phenols, 20 organochlorine pesticides

16 PAHs

10 Organochlorine pesticides

4 Aroclors

6 Phthalate esters

7 Organophosphorus pesticides

5 Fungicides/herbicides

PCB 153

PCB 180 PCB 138 p,p-DDE

Hexachlorocyclohexane Hexachlorobenzene

3 Reference marine sediments 3 Reference soils Topsoil

Soil

Marine sediments

Mussel tissue Air particles

Hexane-acetone (1:1)

Acetone-dichloromethane

Dichloromethane

Dichloromethane-toluene (50 : 50)

Acetone-hexane (50: 50)

Reference marine sediments Hexane-acetone (1:1)

Reference marine sediments Dichloromethane

Fly ash Soil

Marine sediments

Reference marine sediment Reference soil Reference river sediment Reference sewage sludge Industrial soil Marine sediment

Sediment saturated with distilled water (1 g sample and 2 mL water)

Topsoil Clay soil Sand

Reference soil

Water samples preconcen-trated on C18 membrane discs

Hexane-acetone (90 : 10) Acetone

Dichloromethane Acetone-hexane (1 : 1)

Dichloromethane Dichloromethane-toluene (50 : 50)

Acetonitrile Isooctane

Isooctane-acetonitrile (1 : 1)

Acetone

Dichloromethane

Seal Blubber

Pork fat Cold liver

Closed-vessel 2,3,4, extraction at 80°C, 41

29 min at 120°C in closed 6 vessel

5 to 40 min irradiation at 30 to 7 90 W in open vessel, 10 min irradiation at 30 W in open vessel

5 min at 115°C in closed 8 vessel

5 to 10 min at 35°C in open 9,10 vessel

70°C in closed vessel

20 min at 120°C, closed vessel

5 and 15 min at 115° and 135°C, closed vessel

10 min, 30 watts, open vessel

11 12

30 s irradiation in open vessel; repeat up to five times

Closed-vessel extraction at 16 115°C for 10 min

1, 3, 5, 10 min at 80°C, 17 100°C, 120°C, closed vessel n-Hexane

Ethyl acetate-cyclohexane

Several 30 s extractions 18 at 1000 W

Several irradiations at 250 to 19 1000 W in increments of 100 W

PCBs

PCBs

Municipal sewage sludge Hexane-acetone (1:1) River sediments Hexane-acetone (1:1)

10 min, 30 W, open vessel 20 15 min, closed vessel 21

Table 3 Continued

Analyte

Matrix

Solvent

MAE conditions

Ref.

C16-C32 hydrocarbons 20 PAHs

4 Organochlorine pesticides PCBs

Phenol

Methyl phenols Nonyl phenol

Phenol

2-Chlorphenol 2-Methylphenol 2-Nitrophenol 2,4-Dichlorophenol

Imidazolinone herbicides

Atrazine and degradation products

Atrazine

Simazine

Prometryne

Atrazine Simazine Metazachlor Desisopropyl atrazine Desethyl atrazine

Atrazine

Organotin compounds (mono-, di- and tributyltin; mono-, di- and triphenyltin)

Organotin compounds

Butyl and phenyl organotin

Organotin compounds

Methylmercury

Marine sediments

Soils

Water samples preconcen-trated on C18-packed cartridge, C18-packed disc Sediments

Soil

Soil

Lupin seeds Rat feces

Sandy loam Clay

Bentonite Florisil

Sand Peat Clay

Soil

2 Reference sediments Sediments

Reference marine biological matrix Tuna tissue Mussel tissue

Sediments

6 min, closed vessel

Hexane and 130°C in closed vessel hexane-acetone (2 : 8) with pyridine and acetic anhydride for in-situ derivatization

Dichloromethane 5 and 15 min at 100°C to

Acetone-petroleum ether 120°C, closed vessel (1:1)

Acetone-hexane (various Closed vessel ratios)

0.1 M ammonium acetate/ammonium hydroxide (pH 9-10)

Water followed by 0.35 N HCI

Methanol

Dichloromethane

Water

Dichloromethane with water, methanol, and acetonitrite Acetonitrite-0.5% ammonia in water (70 : 30)

Water

50% acetic acid Isooctane Methanol Water

Artificial sea water

0.5 M ethanoic acid in methanol

25% tetramethylammonium hydroxide in water

11 M acetic acid NaBEt4

Organomercury compounds Sediments

2 M nitric acid 2 M hydrochloric acid Reference biological materials 25% tetramethylammonium hydroxide

Aquatic sediments Certified reference sediments

Digestion with 6 M HCI (methylmercury is extracted at room temperature by complexa-tion with cysteine acetate and toluene)

3 to 10 min irradiation at 125°C in closed vessel

Closed vessel, 95-98°C

3, 4 and 5 min closed vessel

1 to 7 min irradiation in open vessel, up to 160 W

3 min, open vessel

3 min at 50 to 60 W, open vessel

3 min at 60 W, open vessel

2 to 4 min at 40 to 60 W, open vessel

10 min at 120°C, closed vessel

27-29

of the solvent. (The recovery of dichlone from solvent was only 5.5% after heating at 145°C for 5 min and 2.6% after 20 min at the same temperature.) Microbial degradation may be responsible for the low recoveries of captafol and captan, whereas in the case of dichlone, it is quite likely that this compound is not stable under the conditions used. Nonetheless, these recoveries are higher than those obtained by Soxhlet or sonication extraction.

Water samples can also be extracted by MAE; however, they have to be preconcentrated first on a membrane disc or some adsorbent material. Chee et al. used C18-membrane discs and then extracted the discs with 20 mL solvent (acetone and dichloro-methane) in a closed-vessel MAE system at 80°C, 100°C and 120°C for 1, 3, 5 and 10 min. Acetone was found to give higher recoveries than dichloro-methane. This approach would allow extremely low detection limits since several discs generated by processing a large volume of sample can be extracted in one vessel.

Vetter and coworkers extracted OCPs from fatty tissues (e.g. seal blubber) with solvents such as hexane and ethyl acetate (1 : 1). To transfer heat to hexane, which is microwave transparent, discs of Weflon™ (2.5 cm in diameter x 0.3 cm thickness) were used in the extraction vessel. The yield of ex-tractable fat and recoveries of OCPs after seven irradiation cycles were comparable to those obtained by Soxhlet extraction. Since ethyl acetate-cyclo-hexane (1:1, v/v) seems to extract more fat than hexane, a gel permeation chromatography step after extraction is a must.

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