Following an in-house study in May 2021, we have updated our qEV cleaning instructions to increase the effectiveness and improve the ability to re-use the columns, as well as being time-effective.
For the best cleaning of your qEV columns, we now recommend:
- qEVoriginal: 10 mL 0.5 M NaOH followed by 20 mL buffer.
- qEV2: 90 mL buffer, followed by 2 mL 0.5 M NaOH, followed by 90 mL buffer.
- qEV10: 140 mL buffer, followed by 5 mL 0.5 M NaOH, followed by 140 mL buffer.
These instructions supersede any given prior to May 2021.
We found that our previous recommendation of cleaning qEVoriginal columns post sample collection with just buffer was giving particle rates from carry over of between 5-40 particles per minute. When the columns are cleaned instead with 0.5 M sodium hydroxide and buffer gave particle rates of <5 particles per minute:
Following this cleaning protocol will minimise the carryover between column uses better than flushing with buffer alone, and the flush with buffer after the 0.5 M NaOH will normalise the column pH back to your working range for the buffer you are using, leaving the column ready to be used again.
For the larger qEV2 and qEV10 columns, it was found that neither buffer nor NaOH and buffer cleaned the column to sub 5 particle per minute cleanliness. However, flushing with 2x column volume of buffer, washing with the maximum sample loading of 0.5 M NaOH and flushing with 2x column volume of buffer again gave <5 particle per minute rates from carryover: