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Repeatability is a very important parameter in gas chromatography analysis. Good instrument repeatability means that the accuracy of quantification and qualitative is directly related to the quality of analysis.
For well-designed instruments, repeatability is guaranteed at the factory 2ml clear GC vials. Although the design of the instrument has an impact on the repeatability, in the actual analysis process, the main factors affecting the repeatability are not the innate conditions of the instrument, but more in the details of the use process.
In the process of using the instrument, we first try to require the maintenance and installation of the instrument according to the instructions and the manufacturer's requirements, to ensure that the instrument can be restored after disassembly and maintenance, so that the sealing of the instrument is guaranteed. A typical example is It is possible to correctly install the graphite pressure ring, O-ring, etc. Secondly, as far as possible, the analyst is expected to be a skilled person using a gas chromatograph - the most important thing is to be able to perform manual injection, if this is not guaranteed, It is recommended that the analyst perform more manual injection exercises; in addition, if the laboratory funds allow, you can purchase equipment such as liquid autosampler, which can eliminate the impact of labor and improve the repeatability of the analysis process.
This article describes the factors that affect the repeatability of gas chromatograph analysis: the injection pad
The injection pad (injection pad, injection septum) is an indispensable component of the instrument inlet, mainly plays a role in sealing the inlet. During the analysis, the injection pad is an important detail that affects the repeatability. factor.
In general, considering the impact of the injection pad on repeatability, it mainly includes the following aspects:
1. The tightness of the injection pad
The tightness of the injection pad refers to the degree to which the instrument injection cap (separator nut) is tightened after the injection pad is installed.
In the actual analysis process, if the injection pad is too loose, it may cause the inlet to leak 2ml clear GC vials; the injection pad is too tight, which may cause the needle to bend or not enter during the injection process, or even if it can be The syringe is inserted into the inlet, and the inlet pressure fluctuations caused before and after the injection also cause poor reproducibility of sample vaporization and splitting.
2, the number of times the injection pad is used
Excessive use of the injection pad can result in leaks in the inlet, which can result in poor sample repeatability.
Gas chromatography consumable suppliers can provide a wide range of injection pads, and some injection pads can be used to achieve 400 injections. However, in actual use, good maintenance habits—not how many times they can be used—are the most important because the quality of the different types of injection pads varies, even for high-quality injection pads. There will also be different actual situations.
Good use of the sampling pad includes: (1) prompts to set the number of injections on the instrument; (2) if there is no such function, you can use the ledger according to the frequency of use, or specify daily, weekly or per Replace the first one of the month. This will make it easier to find problems when problems occur 2ml clear GC vials.
The following examples can be found in the effect of the injection pad on the repeatability of the injection:
(1) Simple experiment
During the continuous three-way split injection process, the peak area of ??the solvent peak and the sample peak becomes larger by tightening the sample pad.
(2) The effect of the tightness of the injection pad on the repeatability
In the continuous multiple-split injection process using FID and capillary column, the repeatability is poor, and the peak area and peak height are greatly changed.
After adjusting the injection pad (unscrewing a half turn), re-injection, reproducibility (peak height and peak area) is significantly improved
In the actual analysis process, whether the capillary column or the packed column is used, the tightness of the injection pad has a great influence on the repeatability. However, there may be some differences between instruments of different brands from different manufacturers, and how to tighten them is how to loosen them, and it is difficult to describe them quantitatively. Therefore, it is still necessary for the analyst to explore the instrument according to the instrument he uses, and to understand the instrument is the best way to use the instrument 2ml clear GC vials.
This is the end of the introduction of Factors affecting the repeatability of gas chromatograph analysis: injection pad. I hope it can help you.
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