• Created : 
  • Modified : 
  • Category :  Agilent Knowledge Portal
  • Entry Type :  Article
  • Product Type :  Analytical LC Systems Preparative LC Systems
  • Component :  LC Injectors and Sample Thermostats
  • Product Name :  1100 Series LC System 1200 Series LC System 1260 Infinity II LC System 1260 Infinity III LC System 1260 Infinity LC System 1290 Infinity II LC System 1290 Infinity III LC System 1290 Infinity LC System
  • Task :  Troubleshooting
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Troubleshooting Source of Contamination on Samplers

Answer

This Information Applies To: Agilent HPLC systems

Issue

The presence of ghost peaks can be a symptom of a system contamination issue, caused by accumulation of sample and/or foreign substances in the flow path. It is critical for high sensitivity LC/MS and LC/MS/MS.

In addition to the presence of ghost peaks, some increase in pressure may have been noticed.

 

Background

One common source of contamination and carry-over of peaks from previous sample runs can be caused by worn or contaminated: 

  • Needle,
  • Needle seat,
  • Rotor seal, 
  • Injection valve (stator head).

These parts are all on the sample and flow path, as seen on Figure 1:


Flow Path of Sampler in Mainpass.
Figure 1. Flow Path of Sampler in Mainpass
1. Sample 2. From Pump to Injection Valve, 3. Metering device, 4. Sample Loop, 5. Needle, Needle Seat, 6. To Column from Injection Valve, 7. Solvent, 8. Wash pump, 9. Wash Port

Requirements

Disconnect the column from the instrument and replace it with a restriction capillary, then perform a blank run on your LC system.

  
Confirmation: A blank run is a run with only injecting the solvent that samples are dissolved in. 

A comparison of column vs. no-column blank runs should identify whether the noted contamination is due to carry over from the column. If the ghost peaks still appear on the blank run, then the contamination comes from the system and not the column.

The key system components should be checked thoroughly – such as the column inlet or the autosampler.

Items Required

When facing a contamination, one of its origins can be found in the autosampler, the following parts should be exchanged in this order: 

  • Needle, needle seat
  • Rotor seal
  • Sample loop
  • Stator head

A full list of the required parts for the particular model of autosampler can be found here. 

  
Tips: This troubleshooting should be carried out with freshly made mobile phase and samples (with new vials). If a needle wash is installed, please flush the wash solvent bottle, clean the wash port, and replace the wash solvent. 

Steps to Follow

After completing each of the following steps, a blank run should be performed. If the contamination is still present, proceed to the next step. 

  1. Change the needle and the needle seat. See the following articles for changing:
    1. The G7129X Vialsampler's needle and needle seat,
    2. The G7167X Multisampler's needle and needle seat,
    3. The G4226x/G1367E Autosampler's the needle and needle seat, or
    4. The G1367A-D Autosampler's needle and needle seat, 
  2. Replace the sample loop. 
  3. Bypass the autosampler by joining ports #1 and #6 of the injection valve with a union or a short capillary tubing. 
  4. Purge for 5 mins at with high organic solvents (i.e isopropanol).
  5. Sonicate the injection valve rotor seal, stator face, and stator head.
  6. Change the rotor seal.
  7. Change the stator head.  
      
    Tips: See the specific User Manual for instructions on changing the sample loop/rotor seal for your model of Autosampler.

If you cannot locate the source of contamination after having been through all the steps, please contact your local Agilent Support representative for further technical support.

 

 
Learn how to effectively operate your Agilent Liquid Chromatography: 
 HPLC Learning Paths eLearning course available from Agilent education.

 

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