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Troubleshooting the MSD
3
Chromatographic symptoms
Peaks have flat tops
• Insufficient solvent delay
• Incorrect scale on the display
• Injection is too large
• Electron multiplier voltage is too high
Peaks have split tops
• Bad injection technique
• Injection is too large
Baseline is rising
• Column bleed
• Other contamination
Baseline is high
• Column bleed
• Other contamination
• Electron multiplier voltage is too high
Baseline is falling
A falling baseline indicates contamination is being swept away. Wait until the base-
line reaches an acceptable level. Common causes include:
• Residual water air and water from a recent venting
• Column bleed
• Septum bleed
• Splitless injection time too long (inlet is not properly swept, resulting in excess
solvent on the column and slow solvent decay)
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