Low temperature secondary thermal desorption apparatusIt is the core equipment for analyzing volatile and semi volatile organic compounds (VOCs/SVVOCs), achieving high-sensitivity detection of trace substances through two-stage thermal analysis and low-temperature focusing technology. Its working principle is based on the deep integration of thermal desorption and gas chromatography analysis, mainly divided into two stages: the first stage of thermal analysis, in which the sample tube is rapidly heated at a high temperature of 280 ℃ -300 ℃, and the target compounds on the adsorbent (such as benzene, toluene, bisphenol A, etc.) desorb and enter the secondary system with the carrier gas (helium/nitrogen); In the secondary thermal analysis stage, the compound is enriched in a low-temperature focused cold trap at -30 ℃ to -40 ℃, and then the cold trap is instantly heated to 320 ℃ to achieve narrowband release of the compound. It is synchronized with the gas chromatography (GC) or mass spectrometry (MS) injection port to form sharp chromatographic peaks.

　　Low temperature secondary thermal desorption apparatusRegular maintenance:

1. Adsorption tube maintenance

Cleaning and activation:

Used adsorption tubes need to undergo high-temperature aging (activation) according to standard methods to remove residual VOCs. The activation program should follow the requirements of the adsorbent type (such as Tenax, Carbopack, etc.) (temperature, time, and carrier gas flow rate).

For adsorption tubes with severe pollution or excessive reuse, chemical cleaning or direct replacement should be considered.

Inspection: Regularly check whether the glass wool at both ends of the adsorption tube is loose, discolored, or blocked, and replace it if necessary.

2. Cleaning of injection needle/sample ring (if any)

If the instrument introduces the standard sample through the injection needle or sample ring, it should be regularly rinsed with a suitable solvent (such as methanol) to prevent blockage and cross contamination.

3. O-ring and seal inspection

Check for wear, deformation, or cracks on the fluororubber or graphite O-rings at the adsorption tube bracket, six way valve, transmission line interface, and other locations. Immediate replacement upon discovery of damage is crucial in preventing gas leakage.

4. Filter inspection

Check if the particle filters on the carrier gas and purge gas pipelines are clogged, and replace them if necessary.