Classification of detection systems for gas chromatographs

The gas chromatograph detector is a device that converts the concentration or quality (content) of each component separated by a chromatographic column into an electrical signal (such as voltage, current, etc.) that is easy to be measured, and performs signal processing. The eye of a gas chromatograph is usually composed of three parts: detection element, amplifier, and digital-to-analog converter. The components separated by the chromatographic column enter the detector in turn, and according to the change of its concentration or quality with time, it is converted into corresponding electrical signals, which are recorded and displayed after amplification, and the chromatogram is drawn. The performance of the detector will directly affect the accuracy of the analysis results of the gas chromatograph. According to the response principle of the gas chromatograph detector,

Principle and Application of Gas Chromatograph

The gas chromatograph uses gas as the mobile phase (carrier gas). When the sample is "injected" into the sampler by a micro injector, it is carried by the carrier gas into the packed column or capillary column. Due to the difference in distribution or adsorption coefficient between the mobile phase (gas phase) and the stationary phase (liquid phase or solid phase) in the chromatographic column, under the flushing of carrier gas, the components are repeatedly distributed between the two phases to separate the components in the column, and then the components are sequentially detected by a detector connected to the column according to the physical and chemical characteristics of the components.

Discussion on the External Gas Path Connection of Gas Chromatograph Manufacturers

Some gas chromatographs are randomly provided with a pressure reducing valve, if not, they should be purchased. Two oxygen and one hydrogen pressure reducing valve are used. The two oxygen pressure reducing valves and one hydrogen pressure reducing valve are respectively installed on nitrogen, air and hydrogen steel cylinders (note that the thread of the hydrogen pressure reducing valve is reversed, and the attached O-shaped plastic gasket is added at the interface for sealing). After tightening the screw cap, close the adjusting handle of the gas chromatograph pressure reducing valve (I .e. loosen), and open the high pressure valve of the steel cylinder. At this time, the pressure reducing valve should have instructions. After closing the high-pressure valve, the indicated pressure should not drop, otherwise there is leakage, and it should be eliminated in time (with gasket or raw material seal), sometimes high pressure

Two Different Selection Criteria for Headspace Sampler

Headspace sampler can provide more advantages than manual technology. Through software, users can establish four methods. Users can edit a parameter in any method. Headspace sampler can automatically set up according to these parameters, and then gas chromatography can optimize the analysis conditions according to the characteristics of the analyzed substance. Another advantage is the automatic establishment of methods, including automatic analysis of 50 samples, constant heating of each sample and removal of gas through a heated loop to ensure repeatability of results. Attention should be paid to the following two points when selecting headspace sampler:

What are the ways in which the headspace sampler performs headspace analysis?

In the headspace analysis of headspace sampler, the understanding and preparation of sample properties, the control of sample volume, the setting of equilibrium temperature and equilibrium time, etc., play an important role in how to improve the recovery rate of standard samples. At the same time, in the capillary chromatography analysis of headspace sampler sampling, the method of low temperature column head is generally used to pre-concentrate the samples obtained from headspace sampling, then the method of programmed temperature rise is used, so that good separation effect can be obtained, and a larger volume of gaseous sample can be introduced.

Type of headspace sampler and attention to purchase

Headspace sampling is an effective method for the analysis of volatile components in liquid samples or solid samples, such as the analysis of volatile VOC components in plastic food packaging bags, and the analysis of toxic components in body fluids after people work in toxic environments.