Gas chromatograph laboratory operators need to control the injection technology
In gas chromatograph analysis, we usually use a micro-injector or a six-way valve (tenport valve) for quantitative injection, of course, the use of the autosampler can achieve better repeatability when conditions permit; consider gas chromatography analysis When injecting technology, it is mainly targeted at general-purpose micro-injector injection.
1. Analyze the injection volume
The first amount of injection is that we need to focus on control. Because the gasification temperature, column capacity and the linear response range of the instrument are related to the gas chromatographic analysis, the injection volume should be controlled within the allowable range of the instantaneous separation and the linear response. The instantaneous injection volume of the column flushing method is generally 0.01 to 10 microliters for the liquid sample or the solid sample solution, and the gas sample is generally 0.1 to 10 milliliters. In the quantitative analysis, it should be noted that the injection volume reading is accurate.
(1) Exclude all air in the syringe
When a liquid sample is taken with a micro-syringe, the air can be removed by simply pumping the liquid to the syringe and quickly discharging it back to the sample vial. There is also a better way to exclude all the air in the syringe. It is to replace the syringe with the sample injection injection about 2 times the injection volume 3 to 5 times, draw 2 times the sample and quickly lift it up and the needle tip is up, push The syringe plunger allows the air remaining on the top of the syringe barrel to be drained.
(2) Ensure the accuracy of the injection volume
Use a cleaned syringe to take about 2 times the planned injection volume, push the syringe plunger upward with the needle tip, and absorb the liquid discharged from the needle tip with gauze or test paper until the value of the required injection volume is wiped dry with gauze. At the tip of the needle, the exact liquid volume has been measured. A little more air needs to be pumped into the syringe. If the plunger is pushed inadvertently, the air can protect the liquid from being drained away.
Of course, for gas chromatograph injection of some special sample analysis, a syringe doser is needed to control the injection volume, such as transformer oil chromatograph, natural gas analytical chromatograph, and high purity gas analysis chromatograph.
2, injection method
When inserting the needle, aim it at the center of the hole of the injector to avoid touching the guide tube of the gas chromatograph injector during the needle insertion. Generally, hold the left-handed light-handed syringe with your right hand and insert the needle into the gasket to press the plunger. At the same time, each time the syringe is inserted at the same height as the injector, quickly press the plunger for 1 to 2 seconds, then pull out the tip as quickly and steadily as possible (continue to hold the plunger).
3, injection time
The length of injection time has a great influence on the efficiency of the column. If the injection time is too long, the chromatographic area will be widened to reduce the efficiency of the column. Therefore, for the flushing method, the shorter the injection time, the better, fast forward and fast. But be sure to be steady! Generally it must be less than 1 second. Generally speaking, it is necessary to keep the speed of the front and rear needles consistent, which is beneficial to the reproducibility of the spectrum, especially when comparison is needed.
The above is the technology that the technicians of the gas chromatograph manufacturer of Luchuang Analytical Instrument Co., Ltd. summarizes for the gas chromatograph injection, which is for your reference only. If you have gas chromatograph related requirements, please contact our company 0632-5080618 or visit the company website http:// for consultation!
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