This Information Applies To: Agilent GC Automatic Liquid Samplers
Issue
Unusual issues can occur to a syringe: needle bending during sample injections.
Resolution
Ensure optimal system performance by considering the following options:
Vials and caps
Agilent vials and caps should be used. An improper gripping of the vial could occur when using non-Agilent vials or caps with the wrong dimensions, resulting into problems when the needle is going down into the vial.
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Tips: The Vial Selector Tool can help choosing the right vial per application.
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Syringe size and type
If application permits, switch from a low volume syringes to a 10 μL syringes. A 10 μL syringe with a thicker needle provides better durability and precision.
Narrow gauge needles (26g) bend more easily than larger gauge needles (23g).
A syringe with a PTFE-tipped plunger can also reduce the chances for a bent plunger.
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Tips: Verify that you are using the right Agilent syringes with the Syringe Selector Tool.
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Improper needle guide
If the application requires a cool on-column inlet, make sure that you are using the on-column needle guide (Figure 1). The on-column needle guide provides enhanced support and improved needle guidance. The on-column needle guide can be effectively used also with other inlets when a 5 μL syringe is used.
Figure 1. 7693A automatic liquid sampler needle guides
1. Standard needle guide, 2. on-column needle guide
Needle installation
Verify that the needle is correctly installed and has a secure placement (see the article Removing and Installing a Syringe on the Agilent 7693A Autosampler).
If the needle feels loose during operation, adjust the flange guide and the green part holding the syringe latch (Figure 2). Proper adjustment prevents needle movement, minimizing the risk of bending during injections.
Figure 2. Flange Guide and Syringe Latch.
1. Flange guide, 2. Syringe latch.
Septum Nut
To maintain the elasticity of the rubber septa, avoid over-tightening the septum nut. Excessive tightening can lead to the rubber septa losing its flexibility, causing it to become rigid and hindering the needle's ability to pierce through effectively.For inlet pressures up to 100 psi, tighten the septum retainer until the C-ring lifts about 1 mm above the top surface (Figure 3).
This procedure is adequate for most situations (See the article Replacing the Inlet Septum for Split/Spitless and Multimode Inlets).
Figure 3. Proper distance between the septum retainer and the C-ring
ALS Alignment
If the injector is not correctly aligned, the needle could also bend during injection. If you suspect a problem with the alignment, please proceed to align your ALS system. The alignment process may vary depending on the type of injector you have. See the articles How to Align the Agilent 7693A GC Injector and How to Align the Agilent 7683B GC Injector for specific instructions on aligning each type respectively. If your injector differs from the ones listed, contact your local Agilent service representative for assistance.
Follow the preceding instructions to troubleshoot and resolve needle bending issues in your GC system. If the problem persists contact Agilent customer support for expert assistance.
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Learn how to effectively operate and maintain your Agilent GC system:
Agilent 8860 GC with OpenLab CDS e-learning path available from Agilent education |
