50 Organic compounds in soils, sediments & sludges
Figure 2.4 Sample chromatogram obtained using worst-case column (Source:Author’s files).
samples often exceeded the capacity of the cold trap, and the resultant breakthrough
produced split peaks and generally poor resolution. By trapping on-column, the capacity of the cycrotrap is approximately equal to the capacity of the column. Breakthrough
only occurs with sample loads that would overload the column anyway. The diagram in Figure 2.5 illustrates the approximate temperature at which breakthrough
is experienced on various size columns as a function of solute boiling point. These
curves represent hydrocarbon solutes on methyl silicone columns with film thickness
of 0.25 um (0.20 mm), 1.0 um (0.32 mm) and 3.0 um (0.53 mm).
Cryofocusing traps are often used to interface purge and trap concentrators to gas
chromatographs with capillary columns. The enhanced performance characteristics
of the design provide a significant improvement over previous systems. The use of a
sophisticated cycrotrap with a thermal gradient ensures that the sample will be trapped
and injected with high efficiency.
Askari et al [225] have compared purge and trap, methanol immersion and hot
solvent extraction methods for the determination of volatile organic compound in aged
soil. These workers found that hot solvent extraction is much more effective than the
US Environmental Protection Agency approved purge and trap technique [297, 298].
Other techniques that have been applied to the determination of multi organic components of soil include high performance liquid chromatography-mass spectrometry
Figure 2.4 Sample chromatogram obtained using worst-case column (Source:Author’s files).
samples often exceeded the capacity of the cold trap, and the resultant breakthrough
produced split peaks and generally poor resolution. By trapping on-column, the capacity of the cycrotrap is approximately equal to the capacity of the column. Breakthrough
only occurs with sample loads that would overload the column anyway. The diagram in Figure 2.5 illustrates the approximate temperature at which breakthrough
is experienced on various size columns as a function of solute boiling point. These
curves represent hydrocarbon solutes on methyl silicone columns with film thickness
of 0.25 um (0.20 mm), 1.0 um (0.32 mm) and 3.0 um (0.53 mm).
Cryofocusing traps are often used to interface purge and trap concentrators to gas
chromatographs with capillary columns. The enhanced performance characteristics
of the design provide a significant improvement over previous systems. The use of a
sophisticated cycrotrap with a thermal gradient ensures that the sample will be trapped
and injected with high efficiency.
Askari et al [225] have compared purge and trap, methanol immersion and hot
solvent extraction methods for the determination of volatile organic compound in aged
soil. These workers found that hot solvent extraction is much more effective than the
US Environmental Protection Agency approved purge and trap technique [297, 298].
Other techniques that have been applied to the determination of multi organic components of soil include high performance liquid chromatography-mass spectrometry