Baseline Oscillation in different HPLC and different methods
Hello!We are facing a problem related to oscillation in baseline for HPLC analysis. The problem is occurring in different equipment and different methods of analysis in the same periods (and the period it happens is intermittent)… When the variation occurs the baseline presents cyclic waves. You can see some prints of the chromatograms in the pictures attached.We use Alliance HPLC, Separation Module e2695 / UV/Vis detector 2489Do you have any experience related to this kind of variation in many equipment and method at same time? Could you help me to find possible causes for the problem? 
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Answers
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What is the Mobile phase and wavelength range? Any chance this is a solvent containing TFA?
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Hi, MarcNoble!
You can see the composition of the phases and the wavelength in the table below. According to the analyst responsible for the methods with the baseline variation, the mobile phases used when the problem started for the 4 methods were the same used one day before where we could not see the variation.
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Well, that is a lot of information.... Let me ask a more basic question. If you run a single mobile phase from a single line (A, B, C or D) do you see the baseline issue?
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Looks to me like your baseline ripple could be following your lab's HVAC cycles. Was it cooler outside on day 1 and warmer on day 2? It could be that your detector has a component that is unusually sensitive to this (or perhaps an amp board on its last legs or something). If you get the same response from another system using exactly the same MP batch etc., it's more likely a degassing issue0
