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HTEC-500
Unstable background current. Possible causes are as follows:
• The reference electrode is old.
• The working electrode is not clean enough.
• The gasket of the cell is wet.
• There is a leakage from the cell or from the tubing joints or there is a scratch on the cell block.
• The system or the mobile phase bottle is placed where the temperature is changing dramatically. Do
not put it in direct sunshine or close to wind from an air conditioner.
• A reagent in the mobile phase is not correct.
• The mobile phase that was applied for the previous analysis still remains in the degasser. Use a syringe
to aspirate solution from the drain valve of the pump so that the old mobile phase flows out.
Disconnect the column and wash the line using clean mobile phase.
Occasional keen peak (spike). Possible causes are as follows:
• Salt extracts by mixing the mobile phase and the sample.
• The edge of the gasket is not flat. Change it for a new one.
• There is dust on the gasket.
• An air bubble is trapped in the cell.
• Columns are not held by column clips properly to ground static electrical current.
• Put the waste bottle on the same level as the analyzer.
The peak of a standard sample is lower than usual. Possible causes are as follows:
• The standard has decomposed (oxidized). The standard is not stable when its concentration is low
and it should be prepared just before the analysis.
• The syringe is not clean. Washing using hydrochloric acid is necessary.
• The drain port of the injector is blocked.
• Some unwanted bacteria may have generated in the HTEC-500. Change the tubing and fill up the
degasser with hypochlorous acid overnight and then wash away using an excess volume of ultrapure
water. Take care NOT to allow hypochlorous acid through the HPLC pump.
• The graphite electrode (WE-3G) may have been used with mobile phase of a high methanol
concentration.
Pulsatile flow. Possible causes are as follows:
• There is a leakage from the flow line.
• Columns are not held by column clips properly to ground static electrical current.
• The pump washing port does not contain enough ultrapure water. Please aspirate ultrapure water
into the syringe.
Less reproducibility of the retention time during one day or day to day. Possible causes are as
follows:
• The ion pair and the column haven’t reached a state of equilibrium yet. Continue to allow mobile
phase to flow for a few to several more hours.
• The mobile phase isn’t mixed well.
• The room temperature changes too much.
• The temperature controller of the HTEC-500 has a defect.
