Rezeroing my PDA

Doug

<p><span>Hello,</span></p><p></p><p><span>I have an analysis where I ned to confirm the presence of several dye molecules. They are more readily detected with the UV signal than with MS, but the signal from my PDA dips below zero masking any peaks on several of my chromatograms. I need a means to either rescale the chromatogram or rezero the PDA signal. I am not aware of a means to do either. Is there such a control?</span></p><p></p><p><span>Thanks,</span></p><p></p><p><span>Doug</span></p>

MikeJ

Hi,

Empower 2 has an autozero timed event available for the Aquity PDA in the instrument method/events tab.

Doug

Thanks, Mike. I'm using MassLynx, but it sounds like that function is there too.

Doug

sunqinglong

You can turn off the power of PDA , then turn on it again . Detector can be initialized automatically . you can try this means!

lizh

There is a way to set your MassLynx scale to read negative dips and I think that will solve the problem. I am going to check exactly how and get back to you asap. Please bear with me.

Liz

AJA

From the chromatogram view

Display

View

Normilize Data to: Lowest point

lizh

Here is a full explanation...

If this you are using Masslynx and an ACQUITY PDA, he can reset the PDA baseline shown from the Chromatogram Display menu. The default view is to Normalize the display to the largest peak found AND the baseline at zero. Since a Mass Spec does not have to deal with masses below zero, the default is aimed at the MS detectors. Under the Chromatogram window for the detector display that is of interest (highlighted if multiple channels or functions are seen), choose the top Display menu, then the View selection in the drop down menu, and choose the baseline to be set to 'Lowest Point' in the View window that opens. Under most separation buffer and gradient conditions, this 'Lowest Point" displays the potential drifts of individual wavelengths or Total Absorbance Chromatograms.

Hope this helps,

Liz