Baseline drift and oscillation of a RI detector
Posted: Mon Jan 07, 2019 9:42 am
Hello, everybody!
I have been getting into a trouble with my HPLC, which is made by a Korean company (YL9100, YL instruments), which is not familiar to most of guys here.
This HPLC is used for analysis of organic acids and alcohols in fermentation samples. It is equipped with a vacuum degasser, a quatenary pump (though operated in only isocratic mode), an autosampler, a column oven, and an RI detector.
The condition I use is as follows:
Column: Bio-Rad Aminex HPX-87H + a guard column
Column oven: 50 degC constant
Flow rate: 0.6 L/min
RID Temp: 40 degC
Mobile phase: 5 mM sulfuric acid in HPLC-grade water
The problem is a weird baseline drift immediately after injection, and there is oscillation of a baseline during analysis. I had used Agilent and Waters HPLCs with the same column and solvent in my previous workplace, and I have never seen such drifts in those devices.
This is a problematic chromatogram. The sample was ultrapure water.
This is a magnified version of the above chromatogram.
You can see after around 0.5 min after injection, the RID signal dropped slightly and rose again until the negative peak appeared. It occurs regularly after injection, so I first suspected contamination in the lines somewhere. Also, you can see somewhat larger oscillations from 17 to 26 min.
I have replaced the sample loop and carried out cleaning of pump by flowing pure isopropanol for a hour. I also have cleaned check-valves in pump and an in-line filter by sonication because contamination of the in-line filter was observed. A service officer from the manufacturer visited my lab several times, but he said this phenomenon is normal, which makes me more serious.
I am awating any comment or suggestion. Thanks!
I have been getting into a trouble with my HPLC, which is made by a Korean company (YL9100, YL instruments), which is not familiar to most of guys here.
This HPLC is used for analysis of organic acids and alcohols in fermentation samples. It is equipped with a vacuum degasser, a quatenary pump (though operated in only isocratic mode), an autosampler, a column oven, and an RI detector.
The condition I use is as follows:
Column: Bio-Rad Aminex HPX-87H + a guard column
Column oven: 50 degC constant
Flow rate: 0.6 L/min
RID Temp: 40 degC
Mobile phase: 5 mM sulfuric acid in HPLC-grade water
The problem is a weird baseline drift immediately after injection, and there is oscillation of a baseline during analysis. I had used Agilent and Waters HPLCs with the same column and solvent in my previous workplace, and I have never seen such drifts in those devices.
This is a problematic chromatogram. The sample was ultrapure water.
This is a magnified version of the above chromatogram.
You can see after around 0.5 min after injection, the RID signal dropped slightly and rose again until the negative peak appeared. It occurs regularly after injection, so I first suspected contamination in the lines somewhere. Also, you can see somewhat larger oscillations from 17 to 26 min.
I have replaced the sample loop and carried out cleaning of pump by flowing pure isopropanol for a hour. I also have cleaned check-valves in pump and an in-line filter by sonication because contamination of the in-line filter was observed. A service officer from the manufacturer visited my lab several times, but he said this phenomenon is normal, which makes me more serious.
I am awating any comment or suggestion. Thanks!