Page 217 - Tandem Techniques

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the fibers in the injection port at about 250°C until no peaks could be detected on a blank run.

The analysis was carried out on a Varian Model 3400 gas chromatograph which was coupled to a
Varian Saturn ion-trap mass spectrometer. The capillary column was 30 m long, 250 µm I.D. and
carried a film of SPB-5 stationary phase, 0.5 µm thick. The column was held at 40°C for 5 minutes,
heated to 100°C at 50°/min., then to 275°C at 5°/min. and finally heated to 300°C at 30°/min. where it
was held for 2 min. The injector and transfer lines were held at 250°C. the mass range scanned was 45-
400 mu. A chromatogram showing the separation of all 60 pesticides, using the polyacrylate fiber for
extracting the sample, is shown in figure 5.22. The concentration of each pesticide in the water was 100
ng/liter indicating a very high sensitivity and a very efficient extraction procedure. The authors claimed
a linearity range of 0.1 to 1 µg per liter and demonstrated there was little difference in the extraction
efficiency between the two types of polymer coated fibers.

A similar technique was developed by Vreuls et al. [25] using a macro extraction system involving a an
extraction tube packed with polymeric material. A 1 ml sample was collected in an LC sample loop and
the internal standard added. The sample was then displaced through a short column 1 cm long, 2 mm
I.D. packed with 10 µm particles of a proprietary PLRP-S polymer (styrene-divinylbenzene copolymer)
by a stream of pure water. The extraction column was then dried with nitrogen and the adsorbed
materials displaced into the gas chromatograph with 180 µl of ethyl acetate. The sample passed to a
short retention gap column and then to a retaining column. The GC oven was maintained at 70°C so
that the ethyl acetate passed through the retaining column and was vented to waste. The solutes of
interest were held in the retaining column at this temperature while the ethyl acetate was removed.
When the ethyl acetate had been removed, the temperature was increased and the components in the
residue separated on an analytical column using an appropriate temperature program. The eluents from
the analytical column passed to a QMD 1000 mass spectrometer. An example of the chromatograms
and spectra obtained are shown in figure 5.23