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- Posts: 418
- Joined: Mon Aug 15, 2005 3:06 pm
Good Morning Chromatographers,
I had an interesting situation last night that I thought some of you might find amusing, so I'm sharing. I'm currently running a system wherein I am separating a compound via reversed phase HPLC, detecting with a photodiode array in native form, then derivitizing it post column and detecting it a second time with a fluorescence detector. I know it sounds unusual, but it makes sense for the compound in question given our application for it. I can say no more.
The system itself consists of two Waters 600e pumps (one for the column gradient and one for the post column derivitizing reagent), a 717+ injector, a 996 PDA, and a 2475 fluorescence detector. There is a "T" for the introduction of derivitizing reagent followed by a 2 meter long reaction coil between the PDA and 2475.
Anyway, upon acquiring a chromatogram on the fluorescence detector, I observed some unusual baseline noise as seen in the image below:
Pressure traces were observed and recorded for each pump and neither indicated any problem with either pump. The noise was not observed on the PDA trace. The mobile phases and derivitizing reagents were fully degassed, there were no leaks observed, and the lamp in the 2475 has 412 hours of use. The entire instrument is setup on a battery backup with a line conditioner and everything is grounded properly.
So what's the deal?
I had the reaction coil, which is simply a length of PEEK tubing, coiled and screwed via a small but stout stainless steel clip to the side of one the pumps in an effort to be neat. Apparently, the clip was tight enough on the coil to transmit high frequency vibrations (from the fans and such) through the coil and on to the flow cell in the fluorescence detector, thus causing the baseline noise. I could feel the vibrations in the coil. They were small but unmistakable.
Weird but true. Removing the coil from the clip and letting it hang eliminated the issue.
The moral of the story: Sometimes it's better to let things hang a little loose...or cop a feel on your LC when things look funny.
I had an interesting situation last night that I thought some of you might find amusing, so I'm sharing. I'm currently running a system wherein I am separating a compound via reversed phase HPLC, detecting with a photodiode array in native form, then derivitizing it post column and detecting it a second time with a fluorescence detector. I know it sounds unusual, but it makes sense for the compound in question given our application for it. I can say no more.
The system itself consists of two Waters 600e pumps (one for the column gradient and one for the post column derivitizing reagent), a 717+ injector, a 996 PDA, and a 2475 fluorescence detector. There is a "T" for the introduction of derivitizing reagent followed by a 2 meter long reaction coil between the PDA and 2475.
Anyway, upon acquiring a chromatogram on the fluorescence detector, I observed some unusual baseline noise as seen in the image below:
Pressure traces were observed and recorded for each pump and neither indicated any problem with either pump. The noise was not observed on the PDA trace. The mobile phases and derivitizing reagents were fully degassed, there were no leaks observed, and the lamp in the 2475 has 412 hours of use. The entire instrument is setup on a battery backup with a line conditioner and everything is grounded properly.
So what's the deal?
I had the reaction coil, which is simply a length of PEEK tubing, coiled and screwed via a small but stout stainless steel clip to the side of one the pumps in an effort to be neat. Apparently, the clip was tight enough on the coil to transmit high frequency vibrations (from the fans and such) through the coil and on to the flow cell in the fluorescence detector, thus causing the baseline noise. I could feel the vibrations in the coil. They were small but unmistakable.
Weird but true. Removing the coil from the clip and letting it hang eliminated the issue.
The moral of the story: Sometimes it's better to let things hang a little loose...or cop a feel on your LC when things look funny.
http://the-ghetto-chromatographer.blogspot.com/
