Ionics Instruments 2004 Page 10-8 DLM 30007-08 Rev. A
The IC removal module is the best method to eliminate problems with high
levels of IC for both on-line monitoring and container sampling. If sampling
from a container, remove the IC from the sample as follows:
1. Add a few drops of acid (6 M H
3
PO
4
) to the sample.
2. Use an N
2
or He purge gas to remove CO
2
from the sample.
3. After purging for 5-10 minutes, analyze the sample.
Acidifying the sample and purging may introduce organic impurities into the
sample, so treat a sample of low TOC, deionized water in the same manner as
a blank.
For more information on the IC removal module, contact Ionics Instruments.
Negative or Zero TOC Measurements
If using the analyzer for on-line measurement of low TOC water and getting
zero or negative TOC readings, investigate the IC level of the water. If it is
greater than 10 times the TOC value, refer to the previous discussion
concerning IC concentration greater than TOC. If the reading appears to have
drifted by 5 ppb (or 10 ppb at the most), recalibrate the TC Zero Offset. If the
drift is greater than 10 ppb, check the TC and IC calibration before
recalibrating the TC Zero. Follow the procedures in the Calibration chapter to
calibrate the TC Zero Offset.
Before making any adjustments to your analyzer you should have eliminated
potential operational problems with the instrument as the cause of the
negative values you are experiencing. An improperly functioning instrument
can yield negative results under some circumstances, and this possibility
should be ruled out with the assistance of a Ionics Instrument Business Group
Service Representative.
Examples of instrument conditions that could potentially lead to negative TOC
values are:
• Depleted resin.
• Bubbles in the TC channel.
• Partial or complete channel blockage, resulting in low restriction in
the TC or IC channels.
• High IC levels relative to those of TOC.
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