Weird baseline dips from gradient - Acquity TUV: anyone else

[Rob Burgess]

Has any user experieneced any similar problem to the .bmp file I have attached where they suddenly see odd dips in the baseline when running steep gradients on their Acquity TUV? if so how have you solved the problem or what could be causing it. Is it perhaps a detector / flow cell problem?


For everyone's info:


Black chrom: Acquity (MPA = Millipore Water + 0.1% TFA; MPB = Merck premixed AcN + 0.1%) dips @ about 9.9, 12.2 and 15.9 minutes

Green chrom: Agilent 1100 ( same mobile phase / column and conditions as black chrom) - no dips

Blue chrom: Acquity (MP A - millipore water + 0.1% TFA; MP B = Romil ACN + 0.1% TFA)


This could be probelematic trying to detect low level imps at 0.05% or less and the imp happens to elue at the point of one of these dips so a long term solution would be required.

[img][img]http://i43.tinypic.com/f4r28l.jpg[/img][/img]

[AA]

The magnitude of the dips is tiny, I doubt they would interfere. I see dips of larger magnitude on the green trace (the 1100) between 13 and 15 minutes, you could probably integrate those! I think you are looking for a problem that does not exist.

[oncoming storm]

I get these all the time with one of my methods that has an immediate switch in the mobile phase instead of a true gradient. (Waters system) They weren't there when we developed the method and just appeared. I couldn't figure out why and I checked just about everything from reagent differences to instrument problems. They are still there. But, it doesn't interfere with my chromatography or my quantitation, which still performs to expected standards, so I quit worrying about them. If you figure it out, I'd like to know.

Good luck,

oncoming storm

[danko]

Hi Rob,

Would you please share some of the the method parameters (i.e. gradient scheme/table, detection wavelength and column temperature)? Also, did you record the backpressure during these runs?
Finally – is the picture fully reproducible or do those dips appear spontaneously (at different retention times)?
Btw, the green trace doesn’t seem to represent the same gradient course as the other 2 traces. Was the gradient table altered in that particular case?

Best Regards

[Rob Burgess]

Just so everybody reading on here knows that the problem was in fact due to a "board" problem in the detector housing itself.

Not very easy to pick up by traditional troubleshooting methods I think you'd all agree