Where is the gas chromatography prone to gas leakage?

As we all know, gas chromatography is a gas as a carrier of separation analysis of technical means, in the gas chromatography system, if the sealing problem, gas leakage will have a great impact on the detection results and the system itself.
air leakage, generally divided into air leakage and auxiliary air leakage.
if it leaks, how do I check for leaks? What has changed in the gas chromatography? What parts are leaking? First, according to the size of the air leakage, the method of detecting air leakage can be divided into: 1. Serious gas leakage.
when the gas source is turned on and stable, the obvious air leakage sound such as silk, indicating that there is a large leakage of the gas path.
this time should be the flow of the flow of large, in the air leakage sound appeared near the line connector, with soapy water to check for leakage.
2. General gas leakage.
block the air outlet, observe the roary flow meter in the gas road, the rot can slowly drop to zero, then do not leak gas, otherwise leakage.
or observe the system pressure meter, open the gas source, adjust the output pressure between 0.3-0.6MPa, iso-air stability, block the air outlet, and then close the main valve, within half an hour if the pressure meter has a significant decline, indicating this part of the leakage.
3. Should be segmented detection, step by step to find leaks.
e.g. gas source to rota flow meter or pressure meter between the air route screening, can refer to the above method, block the rota flow meter or pressure meter exit, the rot does not drop to zero or the pressure meter has dropped, and then use soapy water to check for leakage.
to some small precision components such as detectors, can block the exit and pressurized the atmospheric flow, soaked in ethanol, there are bubbles coming out of the air leakage.
, when air leakage, the chromatography has the following changes: 1. Baseline change (1) baseline instability (high noise, constant temperature operation without irregular fluctuations or drift in one direction).
(2) baseline is loud, it may be too high airflow or leakage.
(3) baseline sine wave fluctuations, may be the air flow is unstable, in addition to checking the gas source, but also to exclude whether the air leakage.
(4) the baseline does not fluctuate or drift in one direction during constant temperature operation, these phenomena can first exclude whether the carrier air leakage.
(5) baseline cannot be zeroed.
heat guide detector may be a leak caused by the thermal guide wire is not completely soaked in hydrogen, thermal conductive wire out of balance or has been burned out.
2. Chromatography peak change (1) peak shape is small, retention time is normal, gas leakage or sampler after the chromatography column, sample pad in the sample leakage.
(2) peak shape becomes smaller, retention time becomes longer, from the sampler to the detector in the air path leakage, or the sample pad continuous leakage.
(3) multiple sample reproducible (retention time, peak area, and quantitative results) excluding the sample technology.
, the main components of air leakage 1. The flow rate is too large to be adjusted: (1) there is a leak in the air behind the flow control valve;
2. When the flow rate is too small: (1) if you hear a clear air leakage sound, find a leak in the sound, (2) no obvious air leakage sound, cylinder high-pressure valve pressure is normal, such as the column front pressure is too low and the cylinder low pressure can not be adjusted normally, it means that the pressure relief valve is broken or leaking, other conditions indicate that the air route is blocked.
3. Unstable after flow regulation, under the premise that the cylinder pressure is normal and the column temperature is normal, it is possible: (1) the air leak in front of the gas valve;
, auxiliary gas leakage, the chromatography has the following changes: generally manifested as the chromatography peak response reduction or even no response.
such as when the hydrogen flame ionization detector (FID) is running, the hydrogen and air sources are out of control and the flow rate is unstable, which can lead to irregular fluctuations in the baseline during constant temperature operation.
, auxiliary gas leakage of the main components: such as hydrogen flame detector (FID) point does not catch fire, zuij simple reason, may be nitrogen, hydrogen and air ratio improper or hydrogen leakage.
e.g. if the flow is not normal (the flow is too large not small, too small or the flow is unstable), you can refer to the gas leakage place, the vast majority of the gas road connector, check the gas connection, there are several conditions that may lead to air leakage: (1) the joint close together with dirt (2) the connector gasket is not suitable, (3) the air connection head does not tighten (4) the air valve parts loose, fall off or have dirt, also often lead to air leakage;