Hach QC8500 Series 2, User Manual

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Troubleshooting
• Manifold: The manifold may not match the diagram in the method or the pump tubes
may be a different color. Make sure the correct interference filter is installed.
• Overrange samples: Sample may be too concentrated. Dilute those samples or
choose a different method.
6.4.6 No peaks
When peaks are not present, it is important to determine whether or not the baseline
shows up. This sections assumes that a baseline is present (
Figure 59
).
6.4.6.1 Common causes
• Valve timing settings: Sample is not being injected into the manifold. Check the
valve timing of the method by running some Universal Dye as a sample. If the dye is
injected properly, a peak appears on the screen. If a dye peak appears, then
troubleshoot the chemistry. A dye peak may not appear if the sample loop is too small.
• Reagents: When a peak appears with injected dye, there may be a problem with the
chemistry. Lack of color formation may be caused by reagents and/or standards that
were not made properly.
• Manifold: Make sure the correct pump tubes are in use. Compare the manifold to the
manifold diagram in the method. The use of wrong pump tubes for the method or
erroneous connections could change the chemical reaction. This may cause a very
low or no response at all.
• Detector: The detector may not be functioning properly. Preview the baseline. During
preview, bounce the flow cell and watch for a response on the screen. If bouncing the
flow cell does not cause a response, the detector may not be functioning or may be
unplugged. If the detector is unplugged, the baseline will show on the screen at
exactly zero volts. Make sure that the method is running on the specified channel.
Make sure the lamp is on.
Figure 59 No peaks