The 25mm flow cell is same design as 10 mm flow cell except the pathlength is 2.5X longer. Thus signal is 2.5X larger and sensitivity increases. This works well to improve detection for small peaks, large peaks can go off scale. Also the detector linearity range remains the same and so larger peaks can easily exceed this. The flow cell volume is larger 2400 nL. However for low lvel impurity detection its sensitivity can be very helpful.
I agree with Christine, it can improve sensitivity and the choice depends upon your application. However; if swapping cells care needs to be used as when re-qualifying the system a different chemistry kit needs to used to that used with the standard flow cell.
That is true, the standard necessary to test the 10 mm flow cell would literally too concentrated as the tests are designed to test the full linear range of the flow cell. Once the SOP's have been written to say qualify all your flow cells, you have to. Do you think your Scientific Affairs or Metrology personnel would simply allow a check injection to ensure that alternative flow cell are working as expected? The test could verify the qualification, in this case the longer pathlength flow cell would be checked to ensure it gives 2.5 times the response for the same sample?
Edited by: Elizabeth Hodgdon on Jan 7, 2009