User`s guide

Sampling Techniques
325
If a 1 µL injection of standard solution is to be used, the
concentration of the solution must be approximately 0.1% by
volume. 1 µL of a 0.1% styrene solution contains 0.91 µg
styrene.
If 0.91 µg of styrene had been collected on a diffusive tube over
480 minutes, the atmospheric concentration would have been
0.948 ppm. Therefore, 0.948 (ppm) should be entered into the
data handling system as the “calibration amount” and 480
(minutes) as the “sample amount”.
Uptake Rates on PerkinElmer Tubes
The uptake rates (UP) of the many common solvents on PerkinElmer
tubes have already been determined. These can be obtained from
relevant scientific literature.
1, 2
Information is also available from
the TDE database that details air monitoring methods and includes
many applications of diffusive monitoring using PerkinElmer tubes.
Table 24 Example of Sample Uptake Rates
If the uptake rate data is not available for a particular component, an
“ideal” value for U
P may be calculated using the first equation from
diffusion coefficients published in the literature.
3
1. Methods for the Determination of Hazardous Substances (MDTD)
Series, UK Health and Safety Executive (TDE)
2. Diffusive Sampling Uptake Rates of Perkin Elmer Tubes
, Thermal
Desorption Data Sheet Number 2.(GCA-72), Perkin Elmer (19XX)
Sample and Sorbent Uptake Rate (UP)
Benzene on Porapak Q
1.37 ng ppm
-1
min
-1
Acrylonitrile on Porapak N
1.35 ng ppm
-1
min
-1
Carbon disulphide on Spherocarb
1.9 ng ppm
-1
min
-1
Xylene on Tenax
2.4 ng ppm
-1
min
-1
Chloroform on Chromosorb 102
2.35 ng ppm
-1
min
-1
3. Analytical Chemistry, G. A. Lugg, (1968), 40, p1072-1077