Sample preparation

Sample preparation - context
Sample preparation - motivation
Purpose of sample preparation
Overview of preparation methods
     Liquid liquid extraction (LLE)
     Solid phase extraction (SPE)
     Solid phase microextraction (SPME)
     Purge and trap (PT)
     (Accelerated) Solvent extraction ((A)SE)
     Supercritical fluid extraction (SFE)
     Filter Techniques (FT)
Box 10 Filtration
Box 11 Sorbents
Box 12 Preconcentration
Selftest
Problems
     1) Adsorbents
           Answer
     2) Purge and trap
           Help
           Answer
     3) Solvents for liquid extraction
     4) Concept map
     5) Cargo screening
           Answer
End of chapter

2) Purge and trap

 

Problem:

You got a two-liter water sample from which you intend to extract 1,2-dichloroethane (DCE) by a purge and trap procedure.

2a) How much air would you have to bubble through the water sample in order to extract at least 98% of DCE at 25°C?
The water/air partition constant is KDCE water/air= 4.2 [Lair/Lwater].

2b) Is it possible to use PU foam in order to trap at least 90% of the extracted DCE at 25°C?
Here is a hint: Since you don't know the exact shape of te breakthrough curve, you have to rely on some estimates: 90% extraction efficiency will be reached if the amount of PU is chosen such that half the retention volume of DCE on the foam is still larger than the air volume that is to be extracted. The porosity of the PU-foam typically is 0.98.

 

Help

for problem 2a): Use Equation 103 from the script.

for problem 2b): Use Table 19 from Box 11 in combination with Table 9 in Chapter V (script) in order to get the relevant partition constants. Furthermore, use equation 103 for R. Assume a density of 1kg/L for PU.

 

proceed to answer