144
Fish
0.1 ppb pentachlorophenol in fish tissues. Confirmation of the identity of the chlorophenol was provided by gas chromatography-mass spectrometry. In this method, the
pentachlorophenol is extracted from the acidified sample with n-hexane and then
re-extracted into a borax solution. It is then acetylated by extracting with n-hexane
containing acetic acid anhydride and pyridine. The resulting pentachlorophenyl acetate is analysed by gas chromatography using an electron capture detector.
This extract procedure gave 83-91 % recovery of pentachlorophenol from fish. The
method was used successfully to determine pentachlorophenol at the 0.15-3 mg kg-l
level in fish. Confirmation of identity of the chlorophenol was established by a
combined gas chromatographic-mass spectrometric analysis.
Thin-layer chromatography and gas chromatography have been used to determine
microgram levels of pentachlorophenol, trichlorophenol isomers, and 2,4 dichlorophenol in fish tissue [421].
7.3.6
Chlorinated Insedicides
Gas chromatography has been extensively used for the determination of chlorinated
insecticides in extracts of fish tissue [422-429]. Solvent extraction and clean-up
procedures are summarized in Table 7.12.
Luckas et al. [430] have described a method for determining PCBs and chlorinated
insecticides in fish by the simultaneous use of electron capture gas chromatography
and derivatization gas chromatography. The method is based on the different stabilities of chlorinated insecticides and PCBs towards magnesium oxide in a micro reactor.
Extracts of samples are injected twice, first into a regular gas chromatograph and then
into a gas chromatograph equipped with a micro reactor for derivatization. A ,basic'
chromatogram and a ,derivatization' chromatogram are obtained and the combination of the two chromatograms provided a satisfactory solution.
Chemical derivatization of sample extracts is very convenient. The extracts containing insecticides and PCBs, after the first injection into the gas chromatograph, are
treated with derivatization reagents, the insecticides being converted into derivatives
while the PCBs remain unchanged.
Luckas et al. [430] as a result of these considerations, developed their micro reactor
gas chromatographic technique in which derivatization is carried out insitu. Preheated magnesium oxide affects the rapid quantitative dehydrochlorination of saturated
DDT metabolites to the corresponding DDT olefins [431]. The derivatization products immediately obtained in the gaseous phase by means of the microreactor (with
nitrogen as the carrier gas and magnesium oxide as the catalyst) are comparable with
the products of chemical derivatization with an alkali in the liquid phase, and substances that are stable to treatment with alkali are also not decomposed in the microreactor. Two gas chromatographs, with an all glass system and an electron capture
detector, were used. One chromatograph was equipped with a microreactor for the
derivatization gas chromatography. Luckas et al. [430] extracted the fish with nhexane and cleaned up with sulphuric acid.
A ,basic' chromatogram of an extract of fish sample showed peaks due to r-HCH
and DDT metabolites, but the background suffers from interference from peaks of
Fish
0.1 ppb pentachlorophenol in fish tissues. Confirmation of the identity of the chlorophenol was provided by gas chromatography-mass spectrometry. In this method, the
pentachlorophenol is extracted from the acidified sample with n-hexane and then
re-extracted into a borax solution. It is then acetylated by extracting with n-hexane
containing acetic acid anhydride and pyridine. The resulting pentachlorophenyl acetate is analysed by gas chromatography using an electron capture detector.
This extract procedure gave 83-91 % recovery of pentachlorophenol from fish. The
method was used successfully to determine pentachlorophenol at the 0.15-3 mg kg-l
level in fish. Confirmation of identity of the chlorophenol was established by a
combined gas chromatographic-mass spectrometric analysis.
Thin-layer chromatography and gas chromatography have been used to determine
microgram levels of pentachlorophenol, trichlorophenol isomers, and 2,4 dichlorophenol in fish tissue [421].
7.3.6
Chlorinated Insedicides
Gas chromatography has been extensively used for the determination of chlorinated
insecticides in extracts of fish tissue [422-429]. Solvent extraction and clean-up
procedures are summarized in Table 7.12.
Luckas et al. [430] have described a method for determining PCBs and chlorinated
insecticides in fish by the simultaneous use of electron capture gas chromatography
and derivatization gas chromatography. The method is based on the different stabilities of chlorinated insecticides and PCBs towards magnesium oxide in a micro reactor.
Extracts of samples are injected twice, first into a regular gas chromatograph and then
into a gas chromatograph equipped with a micro reactor for derivatization. A ,basic'
chromatogram and a ,derivatization' chromatogram are obtained and the combination of the two chromatograms provided a satisfactory solution.
Chemical derivatization of sample extracts is very convenient. The extracts containing insecticides and PCBs, after the first injection into the gas chromatograph, are
treated with derivatization reagents, the insecticides being converted into derivatives
while the PCBs remain unchanged.
Luckas et al. [430] as a result of these considerations, developed their micro reactor
gas chromatographic technique in which derivatization is carried out insitu. Preheated magnesium oxide affects the rapid quantitative dehydrochlorination of saturated
DDT metabolites to the corresponding DDT olefins [431]. The derivatization products immediately obtained in the gaseous phase by means of the microreactor (with
nitrogen as the carrier gas and magnesium oxide as the catalyst) are comparable with
the products of chemical derivatization with an alkali in the liquid phase, and substances that are stable to treatment with alkali are also not decomposed in the microreactor. Two gas chromatographs, with an all glass system and an electron capture
detector, were used. One chromatograph was equipped with a microreactor for the
derivatization gas chromatography. Luckas et al. [430] extracted the fish with nhexane and cleaned up with sulphuric acid.
A ,basic' chromatogram of an extract of fish sample showed peaks due to r-HCH
and DDT metabolites, but the background suffers from interference from peaks of