The term Breakthrough Volume has also been referred to as retention
volume and also the specific retention volume. The units of breakthrough
volume are usually expressed as liters/gram. The breakthrough
volume is defined as the calculated volume of carrier gas per
gram of adsorbent resin which causes the analyte molecules to
migrate from the front of the adsorbent bed to the back of the
adsorbent bed.

In order to determine the Breakthrough Volumes for a large number
of organic chemicals the following system was constructed using
an Varian GC with an FID detector as the base system.

Figure 1 - GC Oven for Determination of Breakthrough Volumes

GLT desorption tubes, 1/4 in. O.D. x 4.0 mm I.D. x 100 mm long
were packed with 250 mg of each of the adsorbent resins between
two glass wool plugs. The packed tube was attached between the
injection port and the detector of a gas chromatograph (Figure
# 1) using 1/16 inch O.D. stainless steel tubing and the appropriate
fittings to mate to the GC. In essence we have made a GC column
using the adsorbent resin as the column packing in the short desorption
tube. Helium was used as the carrier gas and a flame ionization
detector was used for the detection of the eluted organics at
GC temperatures between 0 degrees C and 360 degrees C in 20 degree
increments. Approximately one milligram of each of the analytes
was injected in the GC injection port. Carrier gas flow rates
were accurately adjusted and measured using a primary flow calibrator
(Gilibrator TM, Gilian Instruments) between 1.0 mL/min and 500
mL/min to obtain retention times between 0.1 and 5.0 minutes.
The GC oven temperature was accurately controlled to within 5
degrees C using the GC oven temperature controller. From this
data the breakthrough volumes were determined by multiplying the
retention time by the gas flow rate through the adsorbent resin
and dividing this value by the weight of the adsorbent resin (Figure
# 2).

Figure 2 - Calculation of Breakthrough Volumes

A correction was made for the dead volume of the packed tube and
connecting plumbing by injecting a non retained volatile at high
temperature. A minimum of 7 temperature data points were determined
experimentally in triplicate for each of the analytes studied
on each resin. This data was used to construct a plot of the log
of the breakthrough volume (Bv) versus the analysis temperature
(degrees C) This straight line plot was then extrapolated via
linear regression analysis to obtain the breakthrough volume at
the remaining temperatures (Figure # 3).

Figure 3 - Breakthrough Volumes of Alcohols on Tenax® TA

Finally from this data the Breakthrough Volume tables were assembled.
This charts make it much easier to interpret the breakthrough
volumes as a function of temperature and to compare different
analytes on the same resin as well as compare different resins
for the same analyte