What is the cause of baseline drift or noise?
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Baseline drift often appears when there is temperature fluctuations (small variations can cause important baseline drifts) especially with refractive index and conductivity detectors or with UV detectors at high sensitivity.
A mobile phase mixing chamber not working properly will account for uneven mobile phases causing baseline drifts as well. Contaminants or air buildup in the detector cell could also be responsible for baseline drifts/noise.