Media Replacement Accuracy Test Failure

Good afternoon everyone,

We are performing the media replacement accuracy test in our 850-DS Dissolution Sampler Station and our test is failing (specification <=9mL), as per table below:

Friday Run:

# Initial Weight Final Weight Difference Actual Difference
1 1318.53 1309.16 9.37 9.44
2 1304.27 1295.04 9.23 9.30
3 1322.53 1313.72 8.81 8.87
4 1314.02 1305.46 8.56 8.62
5 1321.64 1312.12 9.52 9.59
6 1327.79 1316.99 10.80 10.88
7 1331.36 1322.33 9.03 9.09
8 1315.28 1304.31 10.97 11.05

Today, I just tested 2 vessels and the results were fine. When I tried to run all the vessels again, the difference is even higher now (around 14mL) for all vessels.

Before performing the media replacement test, we cleaned the system by rinse cannula, rinse pump in and out, pump media replacement in and out and performed prime under calibration.

The configuration set is the one used in the IOQ and that we always perform this test every 6 weeks. 

Could you help me to figure out what can be the problem, considering the volume accuracy test is passing, please?

Thank you so much.

Have a nice day.

Best regards,


  • I think the problem could be at the syringes, how are the syringes? Could you see if have leaks? Usually I disconnect the tubes from dissolutor and put tubes without cannula inside a glass with water.
  • Hi Rui,

    Thank you for your reply. 

    I have discarded the syringes because when I do dispense volume accuracy, the results are perfect. And repeating the test today twice, all the vessels for media replacement accuracy are off for approximately 14mL.

    I was thinking that maybe is the media replacement pump, since this happening to all the vessels, but I'm not sure about the diagram and how it works. And what intrigues me is that is replacing more maybe there is a valve that is not working properly in the pump.

    Anyway, I will try to disconnect the tubes and put them in a glass with water. Let's see how it goes.

    Thank you so much. I really appreciated your quick response.



  • Hi Suzany,

    From my experience, problems with media replacement are usually reservoir sensor when customer uses NaOH. Anyways, you could try to clean this reservoir sensor with alcohol if looks rusty. It might be easier to access if you reach it from the right side (removing the side cover). The green mark in picture below shows location of both media replacement and waste sensors.


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