Although the chromatographic injection needle is small but indispensable, the injection needle is the channel connecting the sample and the analytical instrument. With the injection needle, the sample can enter the chromatographic column and pass through the detector for continuous spectrum analysis. Therefore, the sample injection The maintenance and cleaning of the needle is the focus of the analyst's daily attention, otherwise it will not only affect the work efficiency, but also cause damage to the instrument. This article mainly introduces the small knowledge about the injection needle.
The classification of injection needles
According to the appearance of the injection needle, it can be divided into cone-shaped needle injection needle, bevel needle injection needle, and flat-end injection needle.
Cone-shaped needle, used for septum injection, can reduce the damage to the septum, withstand multiple injections, mainly used for autosamplers;
Beveled needles can be used on the injection septum, which is easy to operate. Among them, the 26s-22 needle is suitable for use on the injection septum in gas chromatography;
Flat-head injection needle is mainly used for injection valve and sample pipette of high performance liquid chromatograph.
Sampling method
According to the sampling method, it can be divided into automatic injection needle and manual injection needle.
According to the different analysis requirements of the injection needle in the gas chromatograph and liquid chromatograph liquid, it can be divided into a gas injection needle and a liquid injection needle. Gas chromatography injection needles generally require less injection, and the common injection volume is 0.2-1ul, so the corresponding injection needle is generally 10-25ul. The selected needle is a cone-shaped needle, which is convenient for sample injection operation;
In comparison, the injection volume of liquid chromatography is generally larger, the common injection volume is 0.5-20ul, so the volume of the relative needle is also larger, generally 25-100UL, and the needle tip is flat, in case Scratch the stator.
In chromatographic analysis, the commonly used injection needle is a micro injection needle, which is especially suitable for liquid analysis by gas chromatograph and liquid chromatograph. The total capacity error is ±5%. Airtight performance can withstand 0.2mpa. Divided into two kinds of liquid sampler and liquid sampler. The specification range of the microinjector without liquid storage is 0.5μL-5μL, and the specification of the microinjector with liquid storage ranges from 10μL-100μL. The micro-injection needle is a sophisticated precision instrument.
The use of injection needle
1. Check the sampler before use, check whether there are cracks in the syringe barrel and whether the needle tip is a burr.
2. Remove the residual sample in the injector, wash the injector with solvent 5-20 times, and discard the waste liquid from the previous 2 to 3 times.
3. Eliminate the air bubbles in the sampler, immerse the needle in the solvent, and repeatedly extract the sample. When the sample is removed, the air bubbles in the sampler can change with the vertical change of the tube.
4. When using the sampler, first fill the sampler with liquid, and then drain the liquid to the required injection volume.
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