Ionics Instruments 2004 Page 9-3 DLM 30007-08 Rev. A
TC Zero Offset
NOTE
The TC Zero Offset is part of the calibration procedure only if the analyzer is
being used with water that is less than 50ppb TOC. If the analyzer is being
used off-line or to analyze water that is greater than 50ppb, do not perform this
part of the calibration procedure and proceed to TC calibration.
The TC zero offset corrects for minor differences in the response of the two
CO
2
sensors. This adjustment is critical only for the determination of low-level
TOC concentrations (< 50 ppb). Recalibration of this offset requires the TOC
instrument to be connected on-line to a supply of low TOC, deionized water.
Per Step 2 (8) below, if the instrument has been used for measurement of
higher levels of TOC (TOC > 50 ppb), the instrument must run on-line for at
least 6 hours, preferably overnight, to “clean” the instrument before adjusting
the TC zero offset. If the instrument has been used for lower level TOC
measurements (TOC < 50 ppb), it is not necessary to “clean” the instrument as
part of the recalibration.
Prior to performing any calibration procedure, print the Constants List. From
the SETUP menu, select PRINTER, then PRINT CONSTANTS. Retain this
list for comparison after the calibration is finished.
To recalibrate the TC zero offset:
Step 1 – Connect Analyzer to Low TOC Water Supply:
If the analyzer has been used for sampling from containers or with the
autosampler, follow the procedures below to set-up the analyzer for on-line
measurements. If the analyzer has been running on-line, proceed to Step 2.
1. Set the SAMPLE MODE to on-line sampling in the SETUP menu.
2. Turn the analyzer off with the main power switch.
3. Disconnect both the 1/16"-OD Teflon tubes from the right side of the
analyzer and reconnect the 1/16"-OD stainless-steel tubing from the
sample inlet system to the analyzer inlet and the waste tube from the
waste outlet to the 1/16" barb on the sample inlet system (see the
To Next Page
Loading...