Cold Trap 9000
| The most flexible
Cryogenic trap available on the Market |
 |
Gas chromatography (GC) involves the analysis of volatile organic compounds, that is, material that exist in the vapour phase, at least at the typical GC operationg temperatures between 40 and 300°C. Since Aroma compounds must, by their very nature, leave the food matrix and travel through the air to be perceived, they are generally exellent candidates for analysis by GC. Although many of these compounds may be solvent extracted, distilled, or otherwise isolated from the food matrix, it is frequently preferable to take advantage of their volatility and rely instead on techniques of headspace analysis. Headspace sampling techniques are frequently divided into three broad categories: static headspace, dynamic headspace and purge and trap. In each case, however, the fundamental principle is the same - volatile analytes from a solid or liquid material are sampled by investigating of the atmosphere adjacent to the sample, leaving the actual sample material behind. Analytes sampled by a headspace technique may be trapped using sorbents like Tenax, Graphitized Carbons or Polymers. However trapping by using a cryogenic trap has a lot of advantages. For trace-level applications the presence of background peaks from the sorbent may be a problem. This is accentuated in the analysis of heavier organics, since they require a higher desorption temperature to transfer from the trap to the gas chromatograph. Frequently the desorption parameters become a compromise between temperatures high enough to desorb the analytes efficiently but low enough to minimize artifacts. One solution is to eliminate the sorbent altogether and collect the analytes cryogenically.
Cold Trap 9000 - Principle of operation.
The
main disadvantages of existing Cold Traps on the market is the fact
that pressuized systems need special solenoid valves capable of functioning
at -180°C and due to the pressurised System they need a lot of liquid
nitrogen. The Cold Trap 9000 is designed in a way that no special
solenoid valve is necessary and due to the fact that a Vacuum system
is used the consumption of liquid nitrogen is very low (about 200
ml/run). The Cold Trap 9000 uses a vacuum pump based on a multi stage
ejector using a carrier fluid like pressurized air which allows a
simple and precise adjustement of the refrigeration fluid. The heating
of the Cold Trap 9000 is performed by giving a direct current to a
small tube which allows the system to be heated up from -150°C up
to 300°C in less then 20 seconds, which results in a heating rate
of >1’350°C / minute.
Technical descriptîon
The Cold Trap 9000 may be cooled down between 1 minute 30 seconds
(GC Oven at 50°C) and 4 Minutes (GC Oven at 200°C). The speed in cooling
down the Cold Trap 9000 is therefore related to the GC Oven Temperature.
Heating up the Cold Trap from -150°C up to 300°C may be performed
in less then 20 seconds, which finally results in a heat up rate >1’350°C
which is fairely higher then any other Cold Trap available on the
market.
