High backpressure in a 1260 Infinity II System


We have an Agilent 1260 Infinity II system with the following configuration:

Pump: G7111B

ALS: G7129A with ICC (inner capillaries 0.17 mm)

Detector: G7115A

It works with the following method:

Flowrate: 1 mL/min

Mobile phase:

  • 69.5% ACN
  • 30.5% Ammonium formate/Formic acid 0.03M

Compresibility: 80E-6/Bar

ICC Temperature: 30°C

Column: Perkin Elmer Brownlee SPP C18 2.7 um 150 x 3.0 mm

Normally system works with a pressure of 320 Bar, but in past days pressure suddenly rose above 400 Bar, we thought that column was the culprit but we tried with other columns with the same results (even with a new one). So we looked for other sources for the pressure rising but system pressure without column was around 25 Bar using a ZDV when the system was flushed with water at 1 mL/min flowrate. 

Mobile phases are filtered with 0.45 um membranes and standards and samples are filtered with syringe filters of 0.45 um, solvents are HPLC grade.

PM/OQPV was recently performed with successful results.

Thanks for your help.

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