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I-Class SM-FL: "Sample fluidics over-pressure" during characterization and "sample-pressure low" at injection - WKB7433

Article number: 7433

SYMPTOMS

  • Low pressure followed by high sample pressure failure when resetting the Sample Manager from console.
    • Low pressure failure occurs when "emptying the sample syringe" after washes performed and in preparation for sample draw/aspiration.
    • Intermittent every 40 injections or so. Progressively worsened to an occurrence every 2-3 runs.
  • Replacement sample needle, inject valve, sample loop resolves issue for short period of time.
    • Performance maintenance and operations successful for ~4,000 injections, and then intermittent failures occur.
  • Reproduce the low sample pressure error when making injections.
  • Reproduce the high sample pressure error when calibrating the loop and needle volumes.

ENVIRONMENT

  • ACQUITY I-Class Sample Manager - Fixed Loop (SM-FL)
    • 384 shallow well plates with water covers with 20-ul total sample volumes.
    • Needle placement programmed to 0.8-mm needle depth (from the bottom of the well) to meet residual volume and make 10-ul injections.
    • Chemists centrifuge the plates to spin down the sample protein, but over time. precipitate formed out of solution.

CAUSE

  • Needle placement programmed to 0.6 mm-and 0.8-mm (needle depth from bottom) much lower than specified or as recommended.
    • Lowering the needle placement risk elevates risk of introducing debris or precipitate into the fluidics lines.
    • Suspect sample precipitating in the exchange of strong and weak washes in needle, loop, inject valve, and waste lines.

FIX or WORKAROUND

  • Follow recommendation for 384 well plates:
    • Sample Manager Fixed Loop using 384 well plate (Default Needle Placement of 2 mm) has a residual sample volume of 15 ul in order to make an injection.
      1. Set the needle placement to "automatic" in the instrument/inlet method.
      2. Use minimum 25 ul of sample to reduce risk precipitates/debris clogging Sample Manager fluidics.

ADDITIONAL INFORMATION

 Performance maintenance:

  • Consider more frequent PM schedule running application.
  • Replace sample needle, sample loop, and inject valve as necessary.

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