158
Fish
nature of the sample. This procedure will detect as little as 0.5 ng of dursban, corresponding to a level of 0.01 mg kg-l in a 10 g sample of fish.
Pirimphos methyl (0-{2-diethylamino)-6-methyl-4-pyrimidyl 0,0 dimethyl phosphorothioate) has been determined in fish by a procedure involving gas chromatography of a hexane-acetone extract of the sample [478].
Lores et al. [479] described a method for the determination of fenthion in amounts
down to 0.01 mg kg- 1 in fish. The method involved solvent extraction followed by a
silica gel clean-up procedure, then determination by gas liquid chromatography with
thermionic detection. The clean-up procedure required relatively little time. Recovery
of fenthion exceeded 85 % with adequate sensitivity.
Szeto et al. [480] have described a gas chromatographic method for the determination of acephate and methamidophos residues in fish.
7.3.17
Squoxin (1,1'-Methylene-2-naphthol)
Kiigemagi et al. [481] developed a method for the determination of 0.1 mg kg- 1
residues of this piscicide in fish using derivatization gas chromatography and spectrophotometric methods. Fish were homogenized by grinding with dry ice. The pulverized mixture was poured into a plastic bag which was lightly sealed and placed in a
-10°C freezer overnight to allow the carbon dioxide to sublime. The samples were
stored in this condition prior to extraction. A benzene extract of the fish was treated
with diazomethane to produce the methylated derivative of the piscicide. After concentration, the residue was dissolved in acetonitrile then extracted with hexane prior
to florisil clean-up and gas chromatography, or conversion to a diazo blue B complex
and spectrophotometric evaluation at 552 nm.
7.3.18
Fluridone
A method has been described [482] for the simultaneous determination of underivatized fluridone herbicide and its major metabolite, l-methyl-3-{4-hydroxyphenyl)-5-{3trifluoromethyl)phenyl)-4(lH)-pyridinone, in fish and crayfish tissues by liquid chromatography. Compounds are extracted with methanol, followed by evaporation, acid
hydrolysis to release conjugated residues, liquid-liquid partitioning, purification
using Florisil Sep-Pak, and liquid chromatographic analysis. In the absence of interfering peaks, the detection limit was 0.04-0.05 mg kg- 1 for either compound. In method
validation studies, overall recoveries of fluridone and its metabolite averaged 84 and
70 % in edible crayfish tissues, 74 and 67 % in inedible crayfish tissues, 111 and 103 %
in edible fish tissues and 109 and 76 % in inedible fish tissues, i. e. slightly high recoveries.
7.3.19
Geosmin and 2-Methylisoborneol
Martin et al. [483] have described a method for isolating and quantifying 2-methylisoborneol in fish flesh. Samples of channel catfish flesh were cooked in a microwave
Fish
nature of the sample. This procedure will detect as little as 0.5 ng of dursban, corresponding to a level of 0.01 mg kg-l in a 10 g sample of fish.
Pirimphos methyl (0-{2-diethylamino)-6-methyl-4-pyrimidyl 0,0 dimethyl phosphorothioate) has been determined in fish by a procedure involving gas chromatography of a hexane-acetone extract of the sample [478].
Lores et al. [479] described a method for the determination of fenthion in amounts
down to 0.01 mg kg- 1 in fish. The method involved solvent extraction followed by a
silica gel clean-up procedure, then determination by gas liquid chromatography with
thermionic detection. The clean-up procedure required relatively little time. Recovery
of fenthion exceeded 85 % with adequate sensitivity.
Szeto et al. [480] have described a gas chromatographic method for the determination of acephate and methamidophos residues in fish.
7.3.17
Squoxin (1,1'-Methylene-2-naphthol)
Kiigemagi et al. [481] developed a method for the determination of 0.1 mg kg- 1
residues of this piscicide in fish using derivatization gas chromatography and spectrophotometric methods. Fish were homogenized by grinding with dry ice. The pulverized mixture was poured into a plastic bag which was lightly sealed and placed in a
-10°C freezer overnight to allow the carbon dioxide to sublime. The samples were
stored in this condition prior to extraction. A benzene extract of the fish was treated
with diazomethane to produce the methylated derivative of the piscicide. After concentration, the residue was dissolved in acetonitrile then extracted with hexane prior
to florisil clean-up and gas chromatography, or conversion to a diazo blue B complex
and spectrophotometric evaluation at 552 nm.
7.3.18
Fluridone
A method has been described [482] for the simultaneous determination of underivatized fluridone herbicide and its major metabolite, l-methyl-3-{4-hydroxyphenyl)-5-{3trifluoromethyl)phenyl)-4(lH)-pyridinone, in fish and crayfish tissues by liquid chromatography. Compounds are extracted with methanol, followed by evaporation, acid
hydrolysis to release conjugated residues, liquid-liquid partitioning, purification
using Florisil Sep-Pak, and liquid chromatographic analysis. In the absence of interfering peaks, the detection limit was 0.04-0.05 mg kg- 1 for either compound. In method
validation studies, overall recoveries of fluridone and its metabolite averaged 84 and
70 % in edible crayfish tissues, 74 and 67 % in inedible crayfish tissues, 111 and 103 %
in edible fish tissues and 109 and 76 % in inedible fish tissues, i. e. slightly high recoveries.
7.3.19
Geosmin and 2-Methylisoborneol
Martin et al. [483] have described a method for isolating and quantifying 2-methylisoborneol in fish flesh. Samples of channel catfish flesh were cooked in a microwave