When installing a new device, we draw attention to the tips for using your Micro GC Fusion.
This modular technology is very robust. A device can perform millions of measurements without requiring any maintenance.
To use your device in the best conditions, just follow the 4 golden rules:
- Quality of the carrier gas
- Vector gas pressure
- Sample quality
- Sample pressure
Today we will be interested in the first rule: The Quality of the Vector Gas!
Purity 99,9995% or more (equivalent Alpha gas 1 or 5.5 depending on the supplier).
MicroGC can work with different gases depending on the applications. In the order of popularity: helium, argon, hydrogen or nitrogen.
The vector gas, which circulates in the columns of each of the analytical modules of your Micro GC is essential.
The quality of a vector gas is its purity. 99,9995% purity: this means that your gas contains less than 0.0005% impurities.
These impurities are generally moisture, air (O2 and N2) and trace hydrocarbons (HC). If you have any doubts about the quality of the gas you are using, you will find information on this on the bottle.
Here are some tips about the vector gas: the gas passes through the chromatographic column and then over the detector.
These two elements can be affected by poor quality gas.
First the column: it can be sensitive to some compounds.
Take the example of the molecular sieve column. This column separates the so-called permanent gases (H2, O2, N2, CH4, CO...).
But this column retains moisture. It is also molecular sieve that is used in gas purification filters that are sometimes found in laboratories.
If your vector gas contains moisture, the column will act as a filter. And load in water that she'll hold!
By retaining this water, which will occupy sites « active » your column, it will lose separator power and become less efficient.
Regeneration will then be required to clean it.
If your vector gas contains oxygen, this can be more damaging to the column because, at high temperature, depending on the type, the stationary phase can be oxidized and irreparably damaged.
For the column, a poor quality vector gas therefore causes variation in retention times and accelerated ageing of the latter.
At the level of the catharometer (μTCD), traces of oxygen can damage the detector filament. In the long term, it can become noisy and, in the worst case, a break in one of the filaments can be observed (which requires its replacement). However, this remains very rare since the detector is equipped with safety.
Less visible but equally important for the user: if your vector gas contains pollutants, the measurement you perform of these same pollutants is affected as much! Indeed, since the TCD compares the pure vector gas (pure-supposed) with the vector gas from the analytical column, it will not be possible to measure less impurity than what the vector gas contains itself. It is precisely for this reason that for measurements of very low levels, a higher grade vector gas is recommended. Sometimes you can even see negative peaks. It is then concluded that the sample is purer than the vector gas (which is obviously not normal ! ).
The purity of the vector gas is therefore paramount as we have just seen for your material and the results you will obtain. But having a good quality bottle is not enough! The purity of this gas must be ensured up to the apparatus. Implementation is therefore very important and often causes problems that can easily be avoided.
Here are some tips:
1 – Check that the connection to your bottle is clean and dry before mounting the pressure regulator.
2 – Use a good quality pressure regulator for your safety. Check the condition of the joint and change it if it is not in perfect condition.
For the column, a poor quality vector gas therefore causes variation in retention times and accelerated ageing of the latter.
Do not use a pressure regulator that has been connected to another gas if possible. If you don't have a choice, perform several drains of the pressure regulator (5-10 inflators / drains) before connecting the gas to the microGC.
3 – Do not use plastic tubes, polymers.
Prefer copper or stainless steel.
Do not use recovery tubes that have seen other fluids (sometimes even liquids!).
The tubes must be clean and perfectly dry. Purify your entire line.
Indeed, microGC consumes very little gas. If the connected tube is full of air, you will remove this air through the apparatus. This will be very long and the quality inside the modules will not be that of the bottle at all. We recommend slightly deserring the fittings at the rear of the device to create a leak, to purge 30s tubes and to tighten, still under flow of vector gas. If these operations are to be performed often, you can add a 3-way valve at the end of the line, which avoids touching the fittings.
4 – If possible, master the entire line from the bottle to the appliance. If the device is connected to a distribution network, make sure that it has been properly purged before installation and that the bottle changes are made in the rules of art in order not to pollute the network. If you use hydrogen generators to power your device, make sure that maintenance is done regularly to ensure that the output gas is clean and dry.
5 - Finally, run a leak test using an electronic leak detector or then test the pressure holding of the network. Avoid liquid for leak detection, if the liquid enters the tube, it can damage the gas analyzer.
