Metrohm 833 IC Liquid Handling Unit - Manual (Page 71)

7.6 Optimizing the dialysis
833 IC Liquid Handling Unit / Instructions for Use 8.833.1003
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7.6 Optimizing the dialysis
7.6.1 Determining the rinsing time
A rinsing time of 2 min is normally sufficient for completely rinsing the
sample and acceptor channels. This time can be increased if
necessary.
7.6.2 Determining the transfer time
The time for transferring the enriched acceptor solution to the sample
loop must be chosen so that the part of the acceptor solution with the
highest ion concentration is transferred to the sample loop. The
following values can normally be used for the optimal transfer time if the
standard accessories are used; they depend on the delivery rate of the
pump:
Mains frequency Optimal transfer time
50 Hz 0.5 min
60 Hz 0.4 min
You should determine the optimal transfer time yourself for each
analytical problem by measuring the individual ion concentrations as a
function of the transfer time and checking them from time to time.
Proceed as follows:
1 First measurement
• Set transfer time in program to 0.2 min and dialysis time to 10
min (see Section 7.3.1/7.3.2).
• Immerse sample aspiration tubing 16 (see Fig. 21) in a
standard containing 10 mg/L of the particular anion or cation.
• Start determination in IC Net and wait until chromatogram has
been evaluated.
2 Further measurements
• Increase the transfer time in the program (see
Section 7.3.1/7.3.2) in steps of 0.1 min until the measured
concentration starts to decrease.
• Carry out measurements as described in item 1.
3 Determine the optimal transfer time
• Plot the measured peak area or concentration as a function
of the transfer and determine the optimal transfer time from
the plot.