Backpressure drop HPLC system


I have a agilent 1200 series with agilent 1260 infinity II.

After ramping my flow 0.2ml/min - 20 min. 0.4ml/min - 20 min and 0.6ml/min 20 min.

And ramping my temperature for the same period of time 30-40-50 °C

The pressure on system is around 66 bar.

The pressure used to be around 59bar. Which already shows. Increase in pressure.

However, the question is :

If I click on the instrument HiP sampler and perform a needle wash 

The pressure drops to 56bar after the wash.

And during injection the pressure goes back to 66bar.

I never noticed this. Is this normal?

This drop in backpressure during a needle wash prior to starting any analysis. ( The needle wash performed was not the one performed during the injection or the injector program).

All the best,


Was this helpful?