Changing the Inlet Liner on a 6820/6890/7820 GC with a Split/Splitless Inlet

Answer

This Information Applies To: Agilent 6820, 6890, 7820A GC systems with a Split/Splitless (SSL) inlet

Issue

Non-volatile sample matrix components will accumulate in the inlet liner and impact on analytical performance. The inlet liner should be changed regularly as part of your routine maintenance schedule. 

Items Required

• O-ring appropriate for your application. See Liner O-Rings for Gas Chromatography
• Angled wrench (for 6890 and 7820A GC inlets; p/n 19251–00100).
• Inlet liner appropriate for your application. See Inlet Liners for GC High Concentration Analyses and Inlet Liners for GC Trace Analyses.

Steps to Follow

Warning: Surfaces exposed to samples may be contaminated, and the inlet is set at high temperatures. Wear appropriate PPE when handling contaminated and/or hot surfaces.

1. Turn off the inlet heating zone and set the oven temperature to 35 °C. When the oven is at 35 °C and the inlet is at a comfortable temperature to touch, turn off the GC oven temperature, inlet temperature, and the inlet gas supply.
2. Using the inlet nut spanner provided with your GC, remove the inlet nut and gently lift the nut and off the inlet liner. Take care not to chip the top of the liner or bend the 1/16" gas tubing connected to the inlet weldment. (See Figure 1).
   
   

   Caution: Wear clean, lint free gloves when handling the inlet liner, O-ring, and cleaned inlet surfaces to prevent contamination with dirt, fibers, and skin oils.

3. Using tweezers, gently separate the O-ring from the metal inlet surface, then carefully lift the inlet line straight up out of the inlet to avoid chipping the liner (Figure 1):
   

   
   
   Figure 1:  Removing the inlet liner.
   

4. Inspect the surface, remove any O-ring residue from sealing surface, and wipe the exposed surface with clean GC-grade solvent
5. Look into the inlet and inspect the gold seal (Figure 2). If the gold seal is discolored and chromatographic anomalies have been observed, replace the gold seal. See these Gold Seal replacement instructions for further details.
   

   
   
   Figure 2: Black arrow indicating the gold seal to inspect.
   

6. Slide a new O-ring 1.5 to 2 cm down onto the replacement liner. The Agilent logo and Spark symbol are inserted face first and face the bottom of the inlet, unless otherwise indicated by the liner print (Figure 3).
   

   
   
   Figure 3: Inlet liner installation direction: 
   1. Top of Inlet 2. Bottom of inlet 3. The exception with flow direction is printed on liner.
   

7. Install the inlet liner and then tighten the inlet nut. (Figure 4)
   

   
   
   Figure 4: Install the inlet liner 

   Tips: The liner O-ring will slide up the liner as the liner is pushed down into the inlet ensuring a correct seal.

8. Turn on the inlet gas supply and allow the inlet and column to purge with carrier gas for 10 to 15 minutes.
   
   

   Caution: Insufficient purging time can lead to residual oxygen (air) remaining in the column. Damage to the stationary phase of the column may occur if the column is heated with oxygen present.

9. Turn on the inlet heating zone, set the oven temperature to the highest ramp temperature in your method, and hold for 10 to 15 minutes. If subsequent runs show contamination, you may need to bake out the inlet.

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