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- Posts: 2
- Joined: Tue Jun 16, 2026 10:08 pm
We are operating a dual column ICS-6000 instrument with 2 systems. Both systems are configured identically for anions with same components, methods, eluent, consumables, etc. The instrument is roughly a year old and was operating fine until I changed out the analytical column in system 2 and a large water dip appeared which interfered with our fluoride peak. I changed out the column on an older system (ICS-2100) at the same time following the same column start-up procedure and did not have any issues with a large water dip. Since the water dip has appeared and causing issues, we have had the instrument PMed so valves/pumps/fittings are all new/changed/checked, changed out the suppressors, and changed out the EGCs (they were running out). I also switched the columns from system 1 to system 2 and vice versa, but still saw the water dip in system 2. I put in another new analytical column in system 2 but had no peaks at all and the baseline was elevated (maybe bad column?) -- reinstalled the previous column and stabilized the system aside from the water dip. We have not tried preparing our standards in KOH eluent or changing out the conductivity detectors (was told it most likely was not the detectors). System 1 background conductivity is 0.18 uS*cm with a typical small water dip, operates optimally.
General operating conditions for both systems:
Flow rate is 0.25 mL/min. Typical operating pressure is around 2500 psi.
Columns are AG-18 and AS-18 2 mm.
Eluent is KOH at 31 mmol - brand new eluent generator cartridge (not manually prepared).
Suppressors have been updated to NGES-A 2 mm. Background conductivity for system 1 is 0.18 uS*cm, and 0.6 uS*cm for system 2 (system 2 has always had a slightly higher background but increased further after the column change that caused the water dip. Changing the suppressor did not help. DI background conductivity with EGC and suppressors off is about 0.16-0.2 uS*cm across both systems.)
What else can I try to reduce the size of the water dip? Where could it be coming from? Is there a fitting or valve that could be causing the dip? Why would changing the column cause the dip? I have so many questions after troubleshooting this for almost 3 months. I have spoken with the manufacturer, and tried several of the recommendations that were made to reduce the water dip but they did not work. I was also suggested that preparing our standards in eluent would eliminate the water dip, but I almost feel like this is a band-aid.
General operating conditions for both systems:
Flow rate is 0.25 mL/min. Typical operating pressure is around 2500 psi.
Columns are AG-18 and AS-18 2 mm.
Eluent is KOH at 31 mmol - brand new eluent generator cartridge (not manually prepared).
Suppressors have been updated to NGES-A 2 mm. Background conductivity for system 1 is 0.18 uS*cm, and 0.6 uS*cm for system 2 (system 2 has always had a slightly higher background but increased further after the column change that caused the water dip. Changing the suppressor did not help. DI background conductivity with EGC and suppressors off is about 0.16-0.2 uS*cm across both systems.)
What else can I try to reduce the size of the water dip? Where could it be coming from? Is there a fitting or valve that could be causing the dip? Why would changing the column cause the dip? I have so many questions after troubleshooting this for almost 3 months. I have spoken with the manufacturer, and tried several of the recommendations that were made to reduce the water dip but they did not work. I was also suggested that preparing our standards in eluent would eliminate the water dip, but I almost feel like this is a band-aid.
