Poor reproducibility, poor peak shape on an ACQUITY UPLC system with TQ Detector - WKB87870

SYMPTOMS

• Poor reproducibility
• Poor chromatographic peak shape
• Insufficient number of points across the peak (less than 10)
• Dwell time set to 0.005 seconds, number of points per second is 7.4

ENVIRONMENT

• ACQUITY UPLC
• Quadrupole MS
• MassLynx

CAUSE

Too many channels are being acquired at the same time to allow for an adequate number of points per second, resulting in an insufficient number of points across the peak.

FIX or WORKAROUND

1. Determine the retention time and base peak width for each peak in the chromatographic separation.
2. Create a function in the MS method with start and end times specific to each chromatographic peak.
3. Add specific MRM channels to each function, but only for the compounds eluting in the time period defined for the function.

ADDITIONAL INFORMATION

The number of points per second acquired depends on the cycle time. The cycle time is the sum of all dwell times plus the interscan and interchannel delay times at any given point in the acquisition. The higher the cycle time, the fewer points per second that can be plotted. When the cycle time is too high, there will be an insufficient number of points to adequately describe the chromatographic peak.