We have 6 different HP1100's in 3 different rooms, that all experience very cylical noise in their baselines. I believe power sources and climate control issues are eliminated because we see this in 3 different rooms. We see it on reverse phase as well as ion-exchange methods. The noise is greatest during isocratic reequilibration at the beginning and end of the methods. Is this something that is just inherant to the HP's, or is there something else going on here? Thanks in advance for any advice.

I can't give you any answers, but I can provide some more questions to ask (you've probably already looked at most of these):

- flow dependence (i.e., do you see the same thing under stop-flow conditions)? If you do, then you can eliminate pumping system or mobile phase problems.

- is the noise pattern "synchronized" in any way among the instruments? If it is, then this points to temperature, powerline, or EM noise problems (don't laugh, I seem to remember one case that was tracked to a nearby radio tower).

- what kind of time period for the fluctuations (seconds, minutes, hours,)? If it's long-term and has a diurnal pattern (e.g., increasing in the morning, then levelling out and the decreasing late in the day), it could be an ambient temperature problem.

- wavelength dependence? If the problem is wavelength dependent, that argues against power line problems; if it's more pronounced at longer wavelengths, it points toward temperature issues (affecting the RI of the mobile phase). If it's more pronounced at shorter wavelength, then it points toward mobile phase mixing issues.

- Does the problem go away if you use a "premixed" mobile phase for the equilibration (rather than mixing on-line)? If so, then you are looking at mobile phase mixing for sure. At that point, you need to determine how bad the problem is (i.e., is it within the manufacturer's specs).

Good luck (and let us know what you find so we can all learn from it!)

You should read a message "Vawy baseline, HPLC" from July 21. There is a lot of discusion on a problem you have.

I have seen two different sorts of cases of such noisy baselines. One was definately temperature related, and stopping the draft on the instrument helped. This, however, was with an HP1050, not the HP1100. Related to this is the need to wrap the inlet line to the detector around the detector block a few times to provide a stable temperature of the fluid in the detector. In one case the cell had been made or installed wrong, so the wrappings were on the exit side.

However, the only time I've seen this sort of thing in the HP1100, the cause was the detector lamp. Try changing the lamp and see if the problem goes away.

I was working with a FL-Detector and the Baseline was very noisy. On the same powerline was a Head-Space Sampler with GC, and everytime the sampler was heating the Baseline become noisy. I changed the powerline and problem was solved.

Estabilize electric power with UPS on line
double conversion.

Hi- I am the author of the original question. Does anyone have any advice about altering the "stroke length" in the HP 1100's? An operator claims that this help, but from what I understand, HP does not recommend this.

I have an Agilent 1100 binary pump, and saw "wavy" baseline at low mixing percentages, for example, during a gradient when A% was 0-4%. I was told by Agilent tech support to change the pump draw volume, or stroke length, to it's minimum volume of 20uL, and not the default setting "Auto". They mentioned something about the wavy baseline commonly being seen in binary pumps (but not tertiary or quantenary) with the "Auto" setting. I changed it, and it did take care of the problem for me. Good luck.

Hi. I'm an Agilent expert who helped designed the 1100 binary. I need to know what 1100 detector you are using and I can diagnose your problem quickly.

We are using a VWD (Part #G1314), Crazy Bill. I'm glad to find an expert, because this problem has plagued us for sometime. Thank-you to everyone who has responded. I've learned a lot, and it's nice to know people are willing to help. Would you suggest changing the stroke length?