The usual steps are preparation-precooling-purging-injection-blowback.

Helium was used as a purge gas for bubbling in the sample solution. During continuous gas flow purging, the volatile components of the sample escape with helium and are concentrated by a collector with an adsorbent. After the specified purging time, the whole or quantitative measurement part will enter the collection device. At this time, the purge gas is closed, and the collector is connected to the open gas phase of the GC through the on-off valve, the obtained sample group is rapidly heated for decomposition, and then enters the GC with the carrier gas for separation analysis. It can be simplified as dynamic top extraction-adsorption thermal desorption.

How does it affect purge and trap results?

One is the purge-capture sampler itself, and the other is the GC condition. Among them, the desorption temperature, flow rate, purification time, analysis conditions and other factors should be strictly controlled. The former is the same as ordinary GC. In this paper, a quantitative method of internal standard method and standard addition method is proposed to reduce the influence of operating condition fluctuation on the results.

To ensure accurate measurement results, the following factors must be considered:

Working temperature: the temperature of blowing out, the aqueous solution is mainly blown at room temperature, as long as the blowing is long enough, it can meet the analysis requirements. The collector temperature includes an adsorption temperature and a desorption temperature. The temperature of the coupling line should be high enough to prevent condensation of the sample.

Wind speed and time gate: The wind speed depends on the concentration of the sample in the sample, the interaction between the volatility of the sample and the sample matrix (e. g. solubility) and the adsorption in the trap tube. With the increase of air volume, the reproducibility and sensitivity are improved.

Desorption price: The soft air volume when analyzing the flow rate mainly depends on the column used. Because the desorption temperature is too low, the desorption speed is slow, the desorption is incomplete, and the desorption temperature is higher, which has a certain influence on the stability of the adsorbent and the target compound.

It should be noted that the source of blowing: the purity of helium and nitrogen should be greater than 99.95%, the pressure should be adjusted to 30 ~ 100psi, and connected to the blowing inlet.