analytes to the gas chromatograph allow this high sensitivity. If
such a high sensitivity is not required (quantification at a
concentration of∼0.1-1µg/L or higher), the SPE step can be
avoided.
The cleaning achieved with the LC step is highly satisfactory.
As already mentioned, water samples were taken from the Ebro
River, which is a very polluted river. When the SPE extract of
the fortified sample is injected directly into the gas chromatograph,
many peaks can be seen together with those corresponding to
pesticides. However, when the analysis of the SPE extract is
carried out by on-line LC-GC, the only important peaks in the GC
chromatograms (Figure 6) are those corresponding to pesticides
spiked at 0.1µg/L in the water sample.
The TOTAD interface employed is manual because it was
developed in our laboratory and is being tested in these initial
experiments. However, it can be easily automated by simply
changing the manual valves to automatic valves and connecting
the GC to the LC system. Such automation can be done with most
LC and GC apparatus manufactured nowadays.
The GC retention times remain constant from one LC-GC
analysis to another because the TOTAD interface refocuses the
analytes in the sorbent-packed liner, so that the introduction of
the compounds into the capillary column is similar to that of a
PTV cold splitless injection.
Helium flows in opposite directions during adsorption and
desorption, so that compounds strongly retained by the sorbent
analytes to the gas chromatograph allow this high sensitivity. If
such a high sensitivity is not required (quantification at a
concentration of∼0.1-1µg/L or higher), the SPE step can be
avoided.
The cleaning achieved with the LC step is highly satisfactory.
As already mentioned, water samples were taken from the Ebro
River, which is a very polluted river. When the SPE extract of
the fortified sample is injected directly into the gas chromatograph,
many peaks can be seen together with those corresponding to
pesticides. However, when the analysis of the SPE extract is
carried out by on-line LC-GC, the only important peaks in the GC
chromatograms (Figure 6) are those corresponding to pesticides
spiked at 0.1µg/L in the water sample.
The TOTAD interface employed is manual because it was
developed in our laboratory and is being tested in these initial
experiments. However, it can be easily automated by simply
changing the manual valves to automatic valves and connecting
the GC to the LC system. Such automation can be done with most
LC and GC apparatus manufactured nowadays.
The GC retention times remain constant from one LC-GC
analysis to another because the TOTAD interface refocuses the
analytes in the sorbent-packed liner, so that the introduction of
the compounds into the capillary column is similar to that of a
PTV cold splitless injection.
Helium flows in opposite directions during adsorption and
desorption, so that compounds strongly retained by the sorbent
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