Selection of needle tips
Syringes are of great importance in the operation of GC systems, since the sample is poured in through them from the sample bottle into the inlet. When using syringes, different sources of error can falsify the result. The reason for this is primarily the large selection of inlets from various manufacturers as well as the variety of autosamplers. The following table helps to counteract this problem by opposing possible needle shapes and their corresponding applications.
| Needle tip |
Application |
|
Conical tip (Cone)
|
- Most versatile needle when using autosamplers or inlet septa
- Minimizes the punching-out of septum particles when used with GC autosamplers
|
|
Beveled tip (Bevel)
|
- Standard needle shape for universal fluid transfer
- Ideal for easily pricking the septum during GC analysis with manual injection
- Reduced septic attrition
|
|
Rounded tip with side hole (Side Hole)
|
- The liquid is sucked in and discharged through the side hole
- Often used in headspace applications or for large injection volumes
|
|
LC tip (LC)
|
- The 90°C bevel prevents damage to the rotor seal and the stator in the injection valves
- Can be used with injectors without inlet-septa like MicroSeal
- Also suitable for pipetting liquids
|
|
Dual gauge tip (Dual Gauge)
|
- Smaller OD (0.47mm) in the front area (20mm) allows on-column injection
- Higher OD (0.63mm) in the back enables increased stability in autosampler injection
|
|
Connection of the needle tip
In addition to the selection of a suitable needle tip for the respective application, the connection of the needle to the injection body can also be varied. A distinction is made between fixed needles, interchangeable needles and injection needles with a luer connection. The characteristics of the respective needle types can be found in the table below.
| Tip connection |
Application |
|
Solid needle
|
- Easy to handly
- Economical
|
|
Disposable needle
|
- A bent needle can be easily replaced, which saves costs
- Allows to use a needle with a different outer diameter (OD) or different length/tip
|
|
Luer Connection
|
- Luer-Lock connection for secure connection of luer-lock needles, fittings, syringe filters and pump flushing adapters
- Luer-Tip connection for luer-lock needles and fittings
|
|
Selection guide for syringe plungers
The materials for the production of syringe plungers are divided into metals (stainless steel, titanium/nickel alloys, etc.) and synthetics (PP, PTFE, etc.). Apart from the material, different types of plungers are distinguished as well. The most frequently applied plunger types as well as their application areas are summarized in the following table.
| Plunger type |
Application |
|
Standard plunger (metal)
|
- Stainless steel plungers are individually ingrained on the glass body
- Plungers are not replaceable
- Industry standard
|
|
Gastight plunger (PTFE tipped)
|
- Plunger with PTFE (Teflon®) tip
- Suitable for liquids and gases
- Suitable for gas or headspace applications
- Plungers are replaceable
|
|
Plunger-in-needle (micro volume)
|
- Plunger reaches the tip of the needle
- Sample is only inside the needle (no contact with the glass)
- Ideal for very small sample quantities
|
|
Plunger Protection
|
- Protective sleeve of upper flange helps to prevent the plunger from bending
|
|
Guided Plunger
|
- Extended glass body protects the plunger during injection
- Suitable for students and rough operating conditions
|
|
SuperfleX™ plunger
|
- Made of titanium/nickel alloy
- Unbending plunger
- Ideal for less experienced users
|
|
