Summary:For many laboratories, it is a relatively common thing to use automatic injection needles to complete the sampling work of certain samples. Mastering the automatic injection needle technology is also the skill of laboratory personnel*. Automatic inj......
For many laboratories, it is a relatively common thing to use automatic injection needles to complete the sampling work of certain samples. Mastering the automatic injection needle technology is also the skill of laboratory personnel*.
Automatic injection needle is a necessary tool to complete chromatographic injection. Whether it is manual injection or automatic injection, it is inseparable from the use of injection needle. The principle of the automatic injection needle is the same. In terms of what factors should be considered when choosing an automatic injection needle.
1. Needle length. The design of each chromatographic inlet is different, so you need to use a specific length of injection needle. To transfer the sample from the liner to the chromatographic column in a reproducible manner, the sample needs to be injected into the injection liner to a specific depth, so it is important to select the correct needle length for the specific application. 2.sampling plunger attachment. Most of the push rods are made of stainless steel and have a PTFE needle tip at the end. If not, the injection needle can only be used for liquid injection. There is also a super-elastic push rod that is not easy to bend, so especially when manual injection, it should be made of a softer material than the standard push rod instead of a push rod made of stainless steel. This material can extend the service life. 3. Tip type. The tapered needle tip of the autosampler needle is a universal needle suitable for autosamplers, which can prevent penetration of the sample vial and the septum of the injection port; the beveled needle tip is usually used for manual injection, and the shape of the needle tip helps reduce the penetration of the septum Possibility. The side-hole type needle tip is generally suitable for headspace and large-volume injection; the flat-head needle tip is used for the injector without the injection port septum. 4. The injection needle capacity. The capacity of the injection needle is varied. Generally speaking, if the capacity of the sample used is less than 10% of the capacity of the injection needle, the injection accuracy will be reduced. For liquid injection, the sample capacity range is usually between 0.5 and 3ul, so the common injection needle capacity range is between 5 and 10ul. For headspace sampling, the sample volume usually ranges from 1 to 3ml, so a larger-capacity injection needle is required. 5. Needle diameter. The needle diameter of an automatic injection needle is a measure of the thickness of the injection needle. The larger the number, the thinner the injection needle. In direct injection, since the injection needle must be placed inside the capillary column, it is very important to select the correct needle diameter. If the selected injection needle is larger, the chromatographic column will be broken and the sample cannot be injected into the chromatographic column.
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