Troubleshooting Peak Problems for Lachat Instruments

When operating the Lachat Flow Injection Analysis (FIA) system, the peaks displayed in the Omnion software represent your data. A visual key to system performance, these peaks tell you many things—from concentration of the analyte to issues that must be examined. But what do you do when you don’t see any peaks, or if the peaks look very odd when running an FIA method?

The Lachat Technical Support team recommends these troubleshooting steps for peak problems to keep instrument downtime to a minimum:

Run dye as a sample to easily rule out or confirm valve timing as a problem. (Remember: When running total phosphorous or o-phosphate (P) methods you will not see a dye peak with an 880nm filter.) After running dye as a sample, observe whether you get a peak. Does the entire loop fill with the dye? Is there dye on both sides of the valve when it turns to inject? When the valve turns to inject, does the dye move onto the chemistry manifold? And when on the manifold does it progress smoothly and move in a forward, not backward, direction?

If the dye does not fill the loop, or enter the manifold, then the sample is not reaching the manifold either. More than likely, this means that the valve timing needs to be corrected and can be adjusted by timing the dye to the valve. If the same valve timing worked previously, there may now be a problem with the sample pump tube, the sample line flow or even the valve itself. If a component of the sample line has been changed or replaced, the time to the valve should be checked.

If the dye is visibly injected onto the manifold, but there are still no peaks, verify the detector response (Remember: When running total phosphorous or o-phosphate (P) methods you will not see a dye peak with an 880nm filter.) Do this by pulling the filter or flow cell out of the detector while a run is in progress or during a preview. You should see a significant shift in the baseline since you are interrupting the light path by removing the filter or flow cell component(s).

If there is no baseline change, then there is a detector response problem. However, this is rarely caused by the detector itself and typically involves configuration, cables, lamp, etc. If you encounter a detector response issue and need assistance, note the voltage of the baseline and then contact Lachat technical support.

Even if the dye injection from #1 appears good, you also need to verify the reagent flow. It is possible to get a good dye injection and still have one or more reagents not flowing properly. Unlike the chemistry, the dye does not require proper reagent flow. Check out the following: Are any of the transmission lines for the reagents pulsing? If you pull the line above the liquid level, does the aspirated air move smoothly and towards the manifold? When encountering a reagent flow issue, replacement of the pump tubes should be considered, particularly if this step has not been done recently. Contact Lachat Technical Support for further advice.

If the dye injects properly and the line flow appears good, an additional troubleshooting action to consider is re-preparing standards and reagents. Contamination and exceeding shelf-life can impact peak appearance.

One final option involves verifying that the analyzer’s manifold matches the diagram in the Lachat published method. If a reagent line were inadvertently connected to the wrong part of the manifold or a wrong pump tube is installed, major peak issues would arise. This may be more likely in situations where manifolds are frequently changed on the channel.

If none of these troubleshooting actions help, or if additional assistance is required, contact the Lachat Technical Support team by emailing support@lachatinstruments.com, or calling (800) 247-7613 (US) and (970) 669-3050.