Adjusting for eluent compressibility 3-25
Required materials
•10-mL volumetric flask
• Stopwatch
• Degassed reservoir of selected eluent
Procedure
To adjust for compressibility:
1. Disconnect the 515 pump outlet from the column to eliminate all
system backpressure.
2. Select the flow rate specified by your separations method, then
simultaneously press the Run/Stop key and start the stopwatch.
3. Record the time it takes to fill the flask with the column disconnected.
4. Reconnect the column, then record the time it takes to fill the flask with
the column connected.
5. Determine the percent difference between the times with and without
the column installed. Use the following formula:
If the difference is acceptable for your application, you do not need to
change the Comp parameter.
6. If the percent difference is not acceptable, for example, if the time
measured with the column installed was 9% greater than the time
measured without the column installed, do the following:
a. Press the Menu key until the Comp menu appears.
b. Press Edit/Enter to access the Comp parameter.
c. Press the Up key the number of times equal to the percent
difference (in time), in this example, nine times.
d. Press Menu to store the parameter.
7. Repeat steps 4 through 6 until the collection times are acceptable.
Time with column – Time without column
Time with column
X 100 = % Difference in Time
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