24 Organic compounds in soils, sediments & sludges
recoveries of 60–80% were achieved, except for 2-tert-butyl-4-methylphenol, the mean
recovery of which was rather poor (9%). The adsorption-desorption of phenols in agricultural soils was evaluated, and their clay mineral and organic matter contents were
found to affect the recovery of alkylphenols to a difference extent than those of the
chlorophenols and nitrophenols.
Leopart-Vizoso et al [118] determined phenols and cresols in soil by direct acetylation followed by gas chromatography – headspace analysis. Danis and Albanis et al
[119] also used a technique based on acetylation-gas chromatography. Three gas chromatography detectors were employed: flame ionisation, electron capture and mass
spectrometric.
Talsky et al [120] has described a higher order derivative spectrometric method
for the determination of phenols in soils.
Karasek et al [28] determined phenols in soils by extraction with a mixture of benzene and water modified to pH 10 by the addition of 2-methoxyethylamine. The phenol
in the extract was identified and determined by gas chromatography using a variety of
detectors, including flame ionisation, electron capture and mass spectrometry.
Lopez-Avila et al [91] used microwave assisted extraction to assist the extraction
of phenols from soils.
Sirvent et al [121] have described a simple and efficient method based on high
performance liquid chromatography for the determination of pollutant levels of phenols in soils containing high levels of organic matter. Alkaline extraction with 0.1 M
sodium hydroxide of the phenolic compounds from soil with a high organic content
is followed by their concentration in a highly cross-linked polystyrene-divinylbenzene
sorbent (Bakerbond SDB-) and analysis by high performance chromatography with UV
detection. Detection limits ranged from 13 to 64 µg kg
−1 . The effect of the amount of
soil and analyte concentration is evaluated and quantitative recoveries are obtained
in all the conditions tested. The proposed methodology was validated by comparing
the results obtained with those achieved by applying the official EPA method 3540C
(Soxhlet extraction) and by the analysis of a certified reference soil without significant
differences being observed with regards to recovery rates, although the new method
proves to be faster. The method was applied to the analysis of spiked soils and to the
evaluation of the stability of the analytes in these soils.
In this method the spiked soil samples (1–10 g) were placed into glass tubes and
phenols were extracted with 10 or 20 mL of 0.1 M sodium hydroxide in a rotary mixer
at 30 rpm for 30 minutes at 25 ± 1
◦ C. Alkaline extracts were centrifuged at 2000 rpm
for 20 minutes to separate the soil supernatants, filtered through 0.45 µm cellulose
acetate membrane filters and their pH were adjusted to 6 with hydrochloric acid.
Then, acidified soil extracts were cleaned up and preconcentrated by SPE using SDB-1
cartridges. High performance liquid chromatography at the alkaline extract before and
after SDB-1 clean-up are shown in Figure 2.2. The SPE process was performed as follows: (1) cartridges were conditioned by adding 2 mL of acetonitrile, 2 mL of methanol
and 2 mL of slightly acidified water (pH = 6.0); (2) acidified soil extracts (pH = 6.0)
were passed through the SPE cartridges at 5 mL min
−1 by means of a Minipuls3 peristaltic pump (Gilson, Villiers – Le-Bel, France) fitted with a silicone pumping tubes;
(3) cartridges were then washed with 2 ML of water at pH 6.0 and the remaining
water was eliminated allowing the passage of an air flow through the cartridges for 5
minutes; and (4) the retained phenols were eluted with 3 mL of acetonitrile.
recoveries of 60–80% were achieved, except for 2-tert-butyl-4-methylphenol, the mean
recovery of which was rather poor (9%). The adsorption-desorption of phenols in agricultural soils was evaluated, and their clay mineral and organic matter contents were
found to affect the recovery of alkylphenols to a difference extent than those of the
chlorophenols and nitrophenols.
Leopart-Vizoso et al [118] determined phenols and cresols in soil by direct acetylation followed by gas chromatography – headspace analysis. Danis and Albanis et al
[119] also used a technique based on acetylation-gas chromatography. Three gas chromatography detectors were employed: flame ionisation, electron capture and mass
spectrometric.
Talsky et al [120] has described a higher order derivative spectrometric method
for the determination of phenols in soils.
Karasek et al [28] determined phenols in soils by extraction with a mixture of benzene and water modified to pH 10 by the addition of 2-methoxyethylamine. The phenol
in the extract was identified and determined by gas chromatography using a variety of
detectors, including flame ionisation, electron capture and mass spectrometry.
Lopez-Avila et al [91] used microwave assisted extraction to assist the extraction
of phenols from soils.
Sirvent et al [121] have described a simple and efficient method based on high
performance liquid chromatography for the determination of pollutant levels of phenols in soils containing high levels of organic matter. Alkaline extraction with 0.1 M
sodium hydroxide of the phenolic compounds from soil with a high organic content
is followed by their concentration in a highly cross-linked polystyrene-divinylbenzene
sorbent (Bakerbond SDB-) and analysis by high performance chromatography with UV
detection. Detection limits ranged from 13 to 64 µg kg
−1 . The effect of the amount of
soil and analyte concentration is evaluated and quantitative recoveries are obtained
in all the conditions tested. The proposed methodology was validated by comparing
the results obtained with those achieved by applying the official EPA method 3540C
(Soxhlet extraction) and by the analysis of a certified reference soil without significant
differences being observed with regards to recovery rates, although the new method
proves to be faster. The method was applied to the analysis of spiked soils and to the
evaluation of the stability of the analytes in these soils.
In this method the spiked soil samples (1–10 g) were placed into glass tubes and
phenols were extracted with 10 or 20 mL of 0.1 M sodium hydroxide in a rotary mixer
at 30 rpm for 30 minutes at 25 ± 1
◦ C. Alkaline extracts were centrifuged at 2000 rpm
for 20 minutes to separate the soil supernatants, filtered through 0.45 µm cellulose
acetate membrane filters and their pH were adjusted to 6 with hydrochloric acid.
Then, acidified soil extracts were cleaned up and preconcentrated by SPE using SDB-1
cartridges. High performance liquid chromatography at the alkaline extract before and
after SDB-1 clean-up are shown in Figure 2.2. The SPE process was performed as follows: (1) cartridges were conditioned by adding 2 mL of acetonitrile, 2 mL of methanol
and 2 mL of slightly acidified water (pH = 6.0); (2) acidified soil extracts (pH = 6.0)
were passed through the SPE cartridges at 5 mL min
−1 by means of a Minipuls3 peristaltic pump (Gilson, Villiers – Le-Bel, France) fitted with a silicone pumping tubes;
(3) cartridges were then washed with 2 ML of water at pH 6.0 and the remaining
water was eliminated allowing the passage of an air flow through the cartridges for 5
minutes; and (4) the retained phenols were eluted with 3 mL of acetonitrile.