I'd check for contamination somewhere, because +114 is diagnostic of TFA, as is 113 and 69 (TFA- and CF3- respectively). It could be there is some contamination elsewhere in the line, especially if you have been using the same tubing to connect column to MS for samples containing TFA. Might be worth giving it all a flush, or having some fresh tubing.

The uncommon adduct [M-H+114]- in your LC-MS analysis may result from interactions with a small molecule or fragment, with m/z values of 113 and 69 likely representing cleavage fragments. Investigating fragmentation patterns and consulting relevant literature can help identify potential sources of these adducts and fragments.

The adduct [M−H+114]−[M-H+114]^{-}[M−H+114]− in negative mode mass spectrometry typically indicates the presence of a specific compound or group of compounds that can form a stable complex with a particular ion or moiety that contributes to the 114 Da mass difference.

Potential Interpretations:

Recommendations:

• Check Reference Databases: Look up known compounds that may form such adducts in literature or databases.
• Consider Isomerism: If multiple isomers are possible, consider the structural diversity that could lead to the same adduct.
• Experimental Conditions: Analyze your experimental conditions to determine if any components could influence adduct formation.

The [M-H+114]⁻ adduct you observed in negative mode LC/MS could be due to an uncommon contamination or reagent interaction. Although TFA is not present, the 114 Da addition might be related to other substances or reagents present in your system (e.g., a plasticizer or solvent impurity). The fragment ions at m/z 113 and 69 suggest a specific structure breaking down in a predictable way. It's essential to check for possible contaminants in your solvents, equipment, or even the plant extract itself. You could also run a blank to see if the adduct is present without the sample.

Thanks everyone for your insights. I investigated the fragmentation and these ions do not seem to be related. It might be TFA as some of you suggested. I have seen H2SO4 and H3PO4 adducts before (although neither of these acids has been used in the solvents we usually use).