Static Headspace (HS)
Dynamic Headspace
Spray-and-Trap (ST)
SPME
Membrane Inlet
Purge-and-Trap
Extraction Methods
Advantage : More sensitive than HS
Drawback : 1. Foaming and slowness
of the purging step
2. Large sample volume and
long purging time (10~30 min)
Purge-and-Trap Method
Experimental Aim
To construct an automated ST-
GC system for on-line
determination of dissolved VOCs
in water.
Carboxen 1000 Carboxen 1003
1/16”
Micro-sorbent Trap
Spray-and-Trap Device
Cleaning
Sampling
Mode A
Mode B
Injection
2. Amount of sample
3. Amount of extraction gas that is sampled.
Sensitivity of Mode A
1. Sprying condition
A. Size of droplet
B. Extraction gas flow rate
C. Design of nozzle
D. Introducing a limited amount of sample and extraction gas
Sensitivity of Mode A
Mode A VS. Mode B
A
Purge-and-Trap Device
Analytical conditions for ST and PT
Recoveries of ST methods
Recovery = PTresponse
STresponse
DL, R.S.D, and R2 for BTEX
Species
Chromatograms of ST-GC-ECD
1. CHCl3
2. CCl4
3. CH2Br2
4. CHCl=CCl2
5. CHBrCl2
6. CCl2=CCl2
Conclusion
An automated spray-and-trap device was built in the laboratory.
The studied ST method was validated in comparison with classic PT: recoveries precision, and linearity.
The ST method shows a fast response to abrupt changes in sample quality, which makes it suitable for on-site monitoring of a water body.