The gas sample appears to be uniform, but contains a relatively complex phase composition containing particles of various sizes and sizes, and the pollutants in the atmospheric sample are always in the dynamic equilibrium of the gas phase and the particulate matter.
When gas is analyzed by gas chromatography, there are several methods for direct sampling of gas:
1 syringe sampling
100mL glass syringe is often used in the on-site inspection work. When sampling, first use the on-site air or exhaust gas to wash 3~5 times, then extract 100mL, quickly seal the air inlet with the rubber cap, put the syringe inlet downward, vertically prevent the syringe The internal pressure is slightly greater than atmospheric pressure.
2 sampling bag sampling
Sampling bags that do not react chemically with the contaminated components of the gas, do not adsorb or leak, such as Teflon bags, polyethylene bags and polyester bags should be selected. In order to reduce the adsorption of the sampled component by the sampling bag, a metal film such as silver or aluminum may be lined on the inner wall. The sampling bag can be vacuumed before sampling, or firstly flushed with the on-site gas for 3~5 times, then the sample gas is extracted several times with the syringe, and the air inlet is sealed, and brought back to the laboratory for analysis by gas chromatograph as soon as possible.
3 sampling tank sampling
The sampling principle of the Su code sampling tube system is the same as that of the vacuum bottle. The stainless steel vessel with inert inner wall is used to draw the inner wall.
1. Data should be prepared to indicate the performance of the required method;
2. There should be written analytical steps for other operators;
3. Systematically demonstrate the performance of the method with more than one system or operator, including the desired component and the desired concentration of the analyte; compare experimental data between different time and different laboratories;
4. Data on the expected life of the column and the reproducibility between columns should be obtained;
5. Study abnormal results to correct potential problems;
6. Study all conditions that affect separation (temperature, mobile phase composition, pH, etc.);
Limit the limits of these conditions; propose possible measures for possible problems (insufficient separation of key peaks; increase in run-time, increase in peak retention, etc.). The requirements of these conditions apply to rigorous HPLC standard methods that are accurate, accurate, reliable, and transferable. In other cases, it may be necessary to only require a successful separation or to respond quickly and “roughly†to a particular problem. In this case, there are many suggestions, and it is sufficient to understand and know the true goal of a method to establish a solution.
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