Ghost peaks & bad chromatography

[danastley]

Hi,

During the method development process, I have been getting a weird ghost peak at the beginning of every sample injection. It's happening under various conditions, both gradients and isocratic, and different columns.

Below are some chromatograms - isocratic 50% B with a zorbax column, isocratic 50% B with an acquity column, and a 0-100% B gradient over 1 minute with a zorbax column.

The same ghost peak appears in all of them, and the chromatography is generally messy with a lot of noise or slowly-eluting analyte after the main peak.

Mobile phase A: 0.1% formic acid in water
Mobile phase B: 0.1% formic acid in acetonitrile
Flow rate: 0.5mL/min
Column temperature: 60°C
LC: Shimadzu Prominence LC20-ad XR
MS: Sciex API 4000 QQQ

I recently tuned this compound via syringe infusion. Could the source be contaminated or may there be other reasons for this? Thank you for any suggestions.







Imgur link (the images wouldn't embed properly): https://imgur.com/a/PJX0D4O

[JMB]

Is this the situation that would occur if the injection valve is contaminated with the tune compound; each time that the valve switches, some amount of the contaminant is flushed onto the column.