Baseline drift observed when running a gradient - WKB7200

SYMPTOMS

• Downward-sloping baseline observed during a gradient            

ENVIRONMENT

• Mobile phase A: Water with TFA
• Mobile phase B: ACN
• e2695 Alliance Separations Module
• 2998 Photodiode Array Detector
• Empower 3

CAUSE

Imbalance in the UV absorbance of the mobile phase components

FIX or WORKAROUND

Add modifier to the second mobile phase to balance out the difference.

ADDITIONAL INFORMATION

Note: A given amount of modifier in an aqueous solution may not give the same absorptivity in an organic solution. Trifluoroacetic acid (TFA) is an example where the UV spectrum of TFA is different in water than in acetonitrile. Use TFA in acetonitrile at about 85% of the amount used in water.

Confirm that the gradient is programmed as expected and not changed by accident.