Ametek 933S - Page 90

3-44 | Model 933S UV Analyzer
5. Observe the graph of the concentrations being displayed and compare
it to the top graph in Figure 3-24. The column should be switching
before EtSH begins to elute. The EtSH elution time can be recognized
as the point after H
2
S, COS, and MeSH have all stabilized and where
H
2
S begins to drop and COS and MeSH begin to increase. If it appears
that EtSH is eluting, the Switching Interval is too long.
To change the Switching Interval, view the Column Timing dialog box
and enter a new time. Click OK then Apply. Save the change to EEPROM.
6. If the analyzer is configured with only the standard H
2
S output, it is
likely that the factory default Switching Interval setting will be correct
for the application. Check that the H
2
S concentration has stabilized
into a plateau before the columns switch. If the columns are switching
before the H
2
S concentration has stabilized, the Switching Interval is
too short and should be increased.
7. If the analyzer is configured with the COS output in addition to the
standard H
2
S output, check to ensure the COS concentration has
stabilized into a plateau before the columns switch. If the columns are
switching before the COS concentration has stabilized, the Switching
Interval is too short and should be increased.
8. If the analyzer is configured with the MeSH output in addition to the
standard H
2
S output, check that the MeSH concentration has sta-
bilized into a plateau before the columns switch. If the columns are
switching before the MeSH concentration has stabilized, the Switch-
ing Interval is too short and should be increased. Verify that the EtSH
elution described in Step 5 is not occurring.
To avoid potential interference from EtSH elution, analyzers with the
MeSH output option should be set up to switch the columns as soon
as a reasonably stable MeSH reading is achieved.
Figure 3-23.
Column Timing dialog
box.
Setup (tab)
Column Timing