94 Organic compounds in soils, sediments & sludges
Wang et al [259] have described a method to analyse Pyraflufen-ethyl residues
by high-performance liquid chromatography (HPLC). The UV detector was used for
routine analysis and the ion-trap MS was used to confirm the identity of the compound. The residue levels of the pesticides and its dissipation rate in apples and soil in
an apple orchard of Beijing were also studied. Primary secondary amine and octadecyl (C 18 ) solid-phase extraction (SPE) cartridges were used for the determination of
Pyraflufen-ethyl resides in apples and soil, respectively. The limit of detection was
estimated to be 1.6 ng, and the limit of quantification of pyraflufen-ethyl in the samples was 0.01 mg kg
−1 . Average recoveries were between 90.1 and 102.1% at three
spiking levels of 0.01, 0.1 and 1 mg kg
−1 , and relative standard deviations were less
than 10% throughout the whole recovery test. A primary secondary amine column was
found to provide effective cleanup for apple extract in the determination of Pyraflufenethyl, and C 18 could remove the greatest number of sample matrix interference in
soil. A dissipation study showed that the half-life obtained for Pyraflufen-ethyl in
soil was approximately 11.89 days at 1.5 times of the recommended dosage, and no
Pyraflufen-ethyl residues were detected in apples in harvest.
In this method soil samples (30 g) passed through a 2 mm sieve and were extracted
by ultrasonic extraction with a mixture of acetone-water (80: 20, v/v, 2 × 60 mL).
The combined extracts were filtered and then concentrated under vacuum with a rotary
evaporator at a bath temperature of 50
◦ C until the final volume reached about 10 mL.
The resultant mixture was dehydrated by passing through a bed containing anhydrous
magnesium sulphate and eluted with acetone. The eluate was then concentrated under
vacuum at 40
◦ C to dryness with a rotary evaporator. The residue of the extracts was
redissolved with 3 mL acetonitrile-water (30:70, v/v) and centrifuged for 5 minutes at
5000 rpm for purification by C 18 cartridges. The C 18 cartridges were connected to a
Visiprep 12-port SPE manifold and conditioned with acetonitrile (5 mL), followed by
distilled water (5 mL). The extract (2 mL) was loaded onto the cartridge and passed
through at a flow rate of one to two drops per second. The cartridge was washed with
acetonitrile-water (3 mL, 50:50, v/v) and then dried with air. The column was eluted
with acetonitrile (3 mL), and the eluate was dried under a gentle stream of nitrogen.
The residue was redissolved in acetonitrile (1 mL) and filtered through a 0.45 µm filter
before HPLC-UV determination. HPLC chromatography obtained by the procedure
is illustrated in Figure 3.11.
St Amand and Girard et al [262] have described procedures for the determination of Acephate and its degradation product methanmidophos in soil by solid
phase extraction followed by GC-M-1. Both of these compounds are highly polar
organophosphorus pesticides (Ops) and are therefore highly soluble in water, which
leads to difficulties when traditional methods of extraction, such as liquid-liquid
extraction, are used. Solid-phase extraction is a relatively new, highly versatile method,
which has proven successful in many cases that were considered problematic in the past.
In this study, several adsorbents (polymeric and silica based) and parameters are considered and modified to obtain maximum recovery. Maximum recoveries are Acephate
and methanmidophos were found to be 90–95% and 85–90% respectively with Oasis
HLB cartridges and methylene chloride as the elution solvent. In order to establish
applicability and reliability, the matrix effect of several real water and solid compost
and soil samples was evaluated. A 20–30% diminution of recovery is noted for some
samples with a complex matrix containing a high amount of dissolved organic matter.
Wang et al [259] have described a method to analyse Pyraflufen-ethyl residues
by high-performance liquid chromatography (HPLC). The UV detector was used for
routine analysis and the ion-trap MS was used to confirm the identity of the compound. The residue levels of the pesticides and its dissipation rate in apples and soil in
an apple orchard of Beijing were also studied. Primary secondary amine and octadecyl (C 18 ) solid-phase extraction (SPE) cartridges were used for the determination of
Pyraflufen-ethyl resides in apples and soil, respectively. The limit of detection was
estimated to be 1.6 ng, and the limit of quantification of pyraflufen-ethyl in the samples was 0.01 mg kg
−1 . Average recoveries were between 90.1 and 102.1% at three
spiking levels of 0.01, 0.1 and 1 mg kg
−1 , and relative standard deviations were less
than 10% throughout the whole recovery test. A primary secondary amine column was
found to provide effective cleanup for apple extract in the determination of Pyraflufenethyl, and C 18 could remove the greatest number of sample matrix interference in
soil. A dissipation study showed that the half-life obtained for Pyraflufen-ethyl in
soil was approximately 11.89 days at 1.5 times of the recommended dosage, and no
Pyraflufen-ethyl residues were detected in apples in harvest.
In this method soil samples (30 g) passed through a 2 mm sieve and were extracted
by ultrasonic extraction with a mixture of acetone-water (80: 20, v/v, 2 × 60 mL).
The combined extracts were filtered and then concentrated under vacuum with a rotary
evaporator at a bath temperature of 50
◦ C until the final volume reached about 10 mL.
The resultant mixture was dehydrated by passing through a bed containing anhydrous
magnesium sulphate and eluted with acetone. The eluate was then concentrated under
vacuum at 40
◦ C to dryness with a rotary evaporator. The residue of the extracts was
redissolved with 3 mL acetonitrile-water (30:70, v/v) and centrifuged for 5 minutes at
5000 rpm for purification by C 18 cartridges. The C 18 cartridges were connected to a
Visiprep 12-port SPE manifold and conditioned with acetonitrile (5 mL), followed by
distilled water (5 mL). The extract (2 mL) was loaded onto the cartridge and passed
through at a flow rate of one to two drops per second. The cartridge was washed with
acetonitrile-water (3 mL, 50:50, v/v) and then dried with air. The column was eluted
with acetonitrile (3 mL), and the eluate was dried under a gentle stream of nitrogen.
The residue was redissolved in acetonitrile (1 mL) and filtered through a 0.45 µm filter
before HPLC-UV determination. HPLC chromatography obtained by the procedure
is illustrated in Figure 3.11.
St Amand and Girard et al [262] have described procedures for the determination of Acephate and its degradation product methanmidophos in soil by solid
phase extraction followed by GC-M-1. Both of these compounds are highly polar
organophosphorus pesticides (Ops) and are therefore highly soluble in water, which
leads to difficulties when traditional methods of extraction, such as liquid-liquid
extraction, are used. Solid-phase extraction is a relatively new, highly versatile method,
which has proven successful in many cases that were considered problematic in the past.
In this study, several adsorbents (polymeric and silica based) and parameters are considered and modified to obtain maximum recovery. Maximum recoveries are Acephate
and methanmidophos were found to be 90–95% and 85–90% respectively with Oasis
HLB cartridges and methylene chloride as the elution solvent. In order to establish
applicability and reliability, the matrix effect of several real water and solid compost
and soil samples was evaluated. A 20–30% diminution of recovery is noted for some
samples with a complex matrix containing a high amount of dissolved organic matter.