Air Conditioner Cause HPLC Baseline Fluctuation, Radiation?

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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Dear all,

I was shocked to find out that the single room air conditioner would cause Agilent 1260 HPLC VWD detector baseline fluctuation yesterday. I could not even believe it.

Every time I turned on the air conditioner, the baseline of a nearby HPLC (2 meter distance) shown a wave, even when I blocked the cool air flow from the AC to reach HPLC. The wave interval is about 10 minutes.

So the only possibility is the radiation emitted by AC cause HPLC VWD problem.

Do you have experienced or heard of this problem? What is the mechanism behind it?

Regards,

Terry
Are you sure the AC and the detector/LC do not share the same circuit or grounding line?
So the only possibility is the radiation emitted by AC cause HPLC VWD problem.


What type of radiation? Electromagnetic?

Likely due to power fluctuations caused by the AC turning on/off.
scottythree wrote:
Are you sure the AC and the detector/LC do not share the same circuit or grounding line?


This was my first thought, too. Many years ago I encountered the same thing on an Agilent 1100 VWD. It turned out HPLC and the AC were on the same circuit and the baseline wave was perfectly in tune with the AC cycling on and off.
Thanks all for your input.

I have asked the electrician to check the power circuit. But I was told that the AC and HPLC is not in the same circuit. They are double checking now.

I will let you know the result.

regards,

terry
even when I blocked the cool air flow from the AC to reach HPLC.
Which would not necessarily stop the ambient temperature at the detector from changing (and a 10-minute cycle time is about what it would take for that to happen).

If this were my problem, I'd stick a thermocouple near the detector cell and record the actual temp as a function of time and see if that syncs with the baseline shifts.
-- Tom Jupille
LC Resources / Separation Science Associates
tjupille@lcresources.com
+ 1 (925) 297-5374
Don't stop at temperature or voltage fluctuations. I've seen an HVAC system that was quite stable with regard to temperature but allowed broad swings in relative humidity over relatively brief periods, which caused baseline fluctuations on my PDA. Our maintenance department thought I was completely out of my mind until I tracked temperature, relative humidity,and my PDA baseline and showed that the peaks and valleys on the PDA correlated perfectly with the swings in humidity. Once I showed the data, they were able to track down the problem and (mostly) solve it.

Good Luck!
http://the-ghetto-chromatographer.blogspot.com/
Several years ago I wrote an article for LCGC on just this topic. It is an interesting story to read through. The final realization of the noise was that it was the HVAC, perhaps an electronic HEPA filter in the ceiling of the lab that was the problem. You can read about this (and other back issues of "LC Troubleshooting") in our compilation called The LC Troubleshooting Bible: http://www.lcresources.com/tsbible This will give you an index of over 300 articles. You want to search (ctrl-F on the Index tab) for Bermuda Triangle (April 2005, p 370). - John
John Dolan
LC Resources
Dear John,

Thanks very much for your article. It is almost exactly what I have been through.

The difference between John and me is that, the space in my lab is very limit. I can not move my HPLCs, I was trying different ways to block the radiation from AC. I have tried steel plate, it was not working very good, I am trying other means.

Regards,

Hai
Just found this old thread and I have exactly the same problem - Air conditioning unit on one wall of a small lab and an Agilent 1100 system with DAD detector about 2.5 meters away. Thanks to this thread I turned off the AC unit and the baseline wave went away. So BIG BIG thanks to you all. (I wonder how many months it would take for me to have worked it out on my own?)

As ever this suggests several questions - is it specifically a problem with Agilent systems? Presumably it is not caused by temperature changes, from John Dolan's article that problem almost seemed to be caused by a fluctuating magnetic field - has anyone a definitive answer as to how these AC units cause this baseline wave?

Thanks again

Chris
chrsdrake wrote:
(I wonder how many months it would take for me to have worked it out on my own?)



It would have worked itself out on it's own by about mid september, if where you are at in the UK has similar climate to here in Montana. :lol:
We had issues when management turned off the AC for the lab just after closing time. Of course, our autosamplers worked through the night and back then our HPLCs (Agilent 1050 systems) could heat but not cool. And the rooms got higher in temperature than the column temperatures in our cGMP-validated methods. So we had to get separate AC for those labs but management didn't care as that came out of a different budget.

Almost like the time that the old whole-lab air compressor was replaced with an oil-lubed compressor, and maintenance swore/promised to maintain the oil catch traps. Then downsizings and vacations caused this to be overlooked, and the air lines in our ENTIRE R&D lab got contaminated with oil (mainly the first-floor labs). Of course cleaning out such lines - if even possible - would've required harmful solvents, special techniques, and high costs. We used house air through a zero air purifier to feed our GC units among other things. Guess what - we had to purchase our own oil-free compressor and pay to have that plumbed into our department.

Remember Dilbert????????????? Cost-savings projects don't always deliver cost savings !!!
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