We recommend that you carefully choose the correct syringe needle tip for your application. Whereas it is also crucial to properly clean your syringe, and choose the correct syringe for your application, a poor choice of syringe tip type may complicate data analysis, or waste your sample.
For example, you may want to avoid shearing off a small component of the injection port septum (known as “coring”). Alternatively, it may be more important to collect as much of your sample from a vial as possible. The following is our brief syringe needle tip guide that is especially pertinent to GC and HPLC applications. We also give advice on preventing your solution dripping from the syringe.
The following is an overview of some common syringe tip types, and their distinguishing features.
- Point Style 2: Sharp, sloping edge tip. May be bent in a manner that partially obstructs the orifice.
- Point Style 3: Blunt tip (90 degree angle).
- Point Style 5: Conical tip with a side hole.
- Point Style H: Domed tip with a side hole.
- Point Style AS: Conical, Blunt tip (90 degree angle)
Next, we discuss the type of syringe needle tip you should use for specific applications, based on the tip design.
1. Routine Sample Uptake (Point Style 3)
We recommend using point style 3. The pertinent feature is that this syringe tip type can reach the bottom of a sample vial. Point style 3 is therefore suitable for when you need to extract the entirety of your sample. In these applications, you are not concerned about the possibility of septum coring.
2. High-Performance Liquid Chromatography(HPLC), Manual Injection (Point Style H)
We recommend using point style H. Special features of this type of syringe tip include:
- Blunt tip syringe needle: Blunt syringe needles minimize the possibility of damage to the HPLC injection port (which could be scratched by a sharp tip).
- Side hole needle: Side port needles are for sample uptake and release. A side hole minimizes the possibility of a piece of the HPLC injection port septum becoming lodged in the syringe needle shaft.
3. Gas Chromatography, Manual Injection (Point Style 5)
We recommend using point style 5. Special features:
- Conical tip. This creates a smooth-cut hole and self-sealing entry point (no coring). Point style 5 therefore may extend the lifetime of your GC injection port septa.
- Side hole. Same purpose as aforementioned (in case some coring does occur).
We advise against using point style 2. The disadvantages of point style 2 are that
- The sharp syringe needle tip may damage the GC injection port, especially when the tip itself is damaged; and
- The septum may be damaged (cored) upon sample injection, which may contaminate your sample. This contamination may introduce artifacts into your data.
These artifacts are commonly known as “ghost” peaks, which researchers typically misinterpret as artifacts that arise from the GC column (as opposed to damaged septa).
4. Auto-Sampling (Point Style AS)
We recommend using point style AS. The blunt syringe tip type is intended to withstand multiple, rapid injections without damaging the instrument injection port (and the conical shape is non-coring).
How to prevent solution dripping
It is also necessary to ensure that no solution drips from your syringe prior to sample injection. There are two easy methods of avoiding this problem:
- Prevent air bubbles. Fully immersing the syringe needle tip in your solution during sample extraction (possibly by holding your solution vial upside down) will help prevent air uptake into the syringe.
- Wait approximately two seconds between sample uptake and removing the needle from your solution. This is typically sufficient time to equalize the pressure in the syringe barrel with the surrounding air.