Plasticizer contamination in LCMS samples - WKB11497

SYMPTOMS

• Samples have strong contaminating peaks at 149 and 338 in positive ion mode. 

ENVIRONMENT

• Synapt G2-Si 
• Xevo G2 ToF

CAUSE

Contaminating peaks are seen at 149 Da and 338 Da. 149 Da is likely to be a phthalate plasticizer, while 338 Da may be erucamide, an agent commonly used in molding plastic. The source of these peaks, and many others, is often the disposable plastic tips used with Gilson-type automated pipettes. Plastic and plastics-related contaminants may be transferred from the pipette tips during sample prep, especially when adding formic acids or other acid additives.

FIX or WORKAROUND

1. Decant a small amount of formic acid or the additive into a clean glass beaker (not from a dishwasher).
2. Draw up and discard three full volumes (depending on the tip size) of formic acid/additive. This should effectively flush the tip, removing plasticizers and molding agents. 
3. Use the flushed tip to add acid/additive to your sample.

ADDITIONAL INFORMATION

This contamination is not limited to the instrument types showing results from sample prep. It can affect any LCMS system.