ACQUITY PDA/2998 fails SQT wavelength accuracy test at 205 nm - WKB95925

SYMPTOMS

• 205 nm wavelength accuracy test failure, successful 273 nm test 
• Flushing with Magic Mix does not resolve
• New flow cell does not resolve 
• Erbium calibration is successful
• M1, M2 mirrors, lamp housing window have been replace and energy at 230nm is 40,000
• Caffeine intensity at 205 is lower than expected and baseline is noisy, while 273 intensity is normal and baseline is flat
•  

ENVIRONMENT

• ACQUITY UPLC PDA Detector
• 2998 Photodiode Array Detector
• Alliance 2695
• Agilent LC

CAUSE

Unknown contaminant in water that absorbs at low wavelength causes test to fail.

Unknown contaminant in methanol that absorbs at low wavelength causes test to fail.

FIX or WORKAROUND

1. Use fresh water in a clean solvent bottle.
2. Use a different high-quality methanol (a new lot number, etc.).   

ADDITIONAL INFORMATION

This has been observed on an instrument that normal runs normal phase solvents and must switch to reverse phase for qualification. Significant flushing may be required. Monitor the baseline at 205 during flushing to see when background is reduced enough to pass.