This is called 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.

• Is your reference electrode more than 1 year old?  If so, it is time to replace it.

  • If the reference electrode is relatively new but having the sin wave, please wrap the glass part of the electrode with a sponge for insulation.  (Eicom provides the insulation material made with plastic for free, please contact us for this part.)

• If the system is placed close to an air conditioner, heater, or other drafts please move the system.  

• Temperature regulation related issue. HTEC-500 shows sometimes very small oscillation. One of the way to prevent this problem is with put a reference electrode cover (RE-Cover) on. Please also confirm if a silicon tubing is put on the ECD inlet. This silicon tube and RE-Cover should be installed as default. If those are installed correctly and the baseline oscillation persists, please set the temperature up for 1 degree. See attached chromatograms of the PP-ODSII application run both with (lower) and without (upper) the RE-COV installed.