Methyl lithium reacts with carboxylic acids to form ketones. So to determine the presence of carboxylic acids, I want to add CH3Li to my sample. I use atmospheric pressure chemical ionization and Q-exactive Orbitrap. I'm worried that introducing this substance will contaminate my mass spectrometer or ionization chamber. Does it provide their contamination?
Dear Zahraa,
You could use succesfully APCI negative mode to detect [M-H] ions
Can you provide more specifically information about yours carboxilic acids?
The great peoformance of API interfaces is that you could obtain generally [M+H]+ ions in positive mode for basic compounds and [M-H]- ions in negative mode for acidic substances. You neednt for any derivatisation.
For ionic compounds (basic or acidic) I reccomend you ESI and for medium to non polar compounds APCI is more suitable.
For example you could use succesfully ESI with HILIC to determine B vitamins and aminoacids abd APCI for caratenoids and Q10 coenzime.
Keep in touch!
What is your workup procedure? During workup, the MeLi might well become methanol or something else, depending on the procedure, and you just need to remove the Li ions.
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