Setting Reagent Flow Rates; Table 4 Acid Flow Rate For Preliminary Measurement With Autoreagent Function - GE Sievers 900 Series Operation And Maintenance Manual

Setting Reagent Flow Rates

GE Analytical Instruments recommends using the Sievers 900 On-Line TOC Analyzer in Autoreagent
mode to ensure the optimum reagent flow rates. In this mode, the Analyzer will automatically
calculate and implement the proper reagent flow rates. This feature greatly simplifies the process
of manually determining optimum reagent flow rates. If you have special operating conditions, you
can operate the analyzer in Manual Reagents mode, and manually select the proper reagent flow
rates for the sample. If you are analyzing ultrapure water (UPW), or have special operating
conditions, you can operate the Analyzer in Manual Reagents mode as described in the section
"Setting Manual Flow Rates" on page 98. Due to the relatively small changes in TOC in UPW, use of
the Autoreagent function will most likely not result in a change to the reagent flow rates.
When the Autoreagent function is active, the Analyzer performs a preliminary measurement of
each new sample before it performs the measurements for which results are reported. The
preliminary measurement is used by the Analyzer to determine the correct acid and oxidizer flow
rates for the subsequent analyses of that sample.
The acid flow rate is set according to the TC and IC concentrations estimated during the preliminary
measurement. These concentrations may not exactly match the results of the subsequent
analytical measurements, but, because there is a range of acceptable flow rates for any given
sample concentration, they are accurate enough to establish the acid flow rate required for the
analytical measurements.
Table 4: Acid Flow Rate for Preliminary Measurement with Autoreagent Function
Results of Preliminary Measurement
TC < 500 ppb
TC ≥ 500 ppb and IC < 50 ppm
IC ≥ 50 ppm
To set the oxidizer flow rate during the preliminary measurement, the oxidizer syringe pump is
turned on at a high flow rate (>20 µL/min) for a short time, and then is turned off. (The actual flow
rate depends on the age of the reagent.) This results in a pulse of persulfate in the sample stream.
As this pulse flows into the oxidation reactor, diffusion causes the concentration of persulfate to
"spread out." The concentration of persulfate in the UV reactor peaks, and then the concentration
gradually decreases. There is a large excess of persulfate at the peak, but the concentration
GE Analytical Instruments ©2009
Selected Acid Flow Rate, µL/min
No ICR or ICR
Bypassed
0.3
1.0
2.0
94 of 236
ICR Inline
N.A.
2.0
4.0
DLM 90488-01 Rev. A