Page 224 - Tandem Techniques
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monitoring, that displays the polycyclic hydrocarbon content of a dust sample, is shown in figure 5.27.
This analysis would be extremely difficult to carry out with any degree of confidence without the
tandem combination. The authors were able to monitor the change in polynuclear aromatic pollution
with both the geographical area and the seasons.
De Beer et al. [29] developed a method for measuring herbicide contaminants in air using a GC/MS
tandem system. They used a collection tube, (32 cm long, 6 mm I.D.) packed with 1 g of an absorbent
resin XAD-2, and a 2 cm plug of silanized glass wool. The glass wool collected the dust particles, and
the resin trapped any herbicide vapors in the air or were desorbed from the particles during sample
3
collection. 5 to 8 m were passed through the trap to collect the sample. 20 ml of n-hexane was pumped
through the trap to elute absorbed material from the resin. The herbicide salts were eluted from the glass
wool and from the particles by washing with four 5 ml volumes of alcoholic caustic soda. The eluates
were concentrated to 10 ml on a rotary evaporator. The extract was then acidified with dilute sulfuric
acid and left for 30 min. at room temperature to hydrolyze the salts to the respective acids.
Figure 5.28
Chromatogram of Derivatized Air Contaminants (a)
Monitored by Electron Capture Detector, (b) Displayed
by Selected Ion Monitoring (ref. 29)
