6.6 Stage 5 – Conditioning the system with buffer
Before processing your sample, precondition the cross-flow system with a buffer similar in pH and
ionic strength to that of your sample. Conditioning the system removes trapped air and minimizes
unwanted chemical reactions between your sample and the wetted parts of the cross-flow system.
You can also use buffer conditioning to stabilize the temperature of the cross-flow system. Follow
these steps to condition the system with buffer:
Step
Action
1
Setup your cross-flow system to circulate the retentate and permeate back to the feed
reservoir (
).
2
Prepare the buffer solution, and if necessary, condition it to the proper temperature. The
recommended volume of buffer solution is 1 liter per cassette.
3
Put the buffer in the feed reservoir. Open the feed, retentate, and permeate valves. Start
the feed pump and increase the feed rate until solution flows from the retentate and
permeate lines.
4
Close the retentate valve to produce about 0.3 to 1 barg (5 to 15 psig) of retentate
pressure. Run until no bubbles appear in the permeate stream.
5
Open the retentate valve and close the permeate valve. Increase the retentate flow rate
to the recommended operating cross-flow rate:
600 to 800 ml/min per 0.11-m
2
(1.2-ft
2
) Kvick Lab cassette
Run until no bubbles appear in the retentate stream.
6
Open the permeate valve. Adjust the retentate valve until the retentate flow is about 10
percent of the feed flow. Adjust the feed pump to maintain a feed pressure of 1.6 to 2.8
barg (25 to 40 psig) for ultrafiltration cassettes.
7
Circulate the buffer for four minutes to condition the system for pH and ionic stability. If
conditioning for temperature control, continue circulating until the temperature of the
system stabilizes.
8
Remove the buffer from the feed reservoir. Keep buffer in other parts of the system to
prevent air from entering the system.
6 Preparing a Cassette for Use
6.6 Stage 5 – Conditioning the system with buffer
38
Learning to Use the Kvick Lab Cassette Holder User Manual 18117269 AI
