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Counterions in LC-MS
Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.
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Hello! I'm new to the forum and have a question regarding the use of counterions in reverse phase LC-MS. Based on the literature I've read, I believe this could improve my peak shape, but I have no experience in this field. What type of counterions can I use when working with MS detector? Also, which concentrations are normally used? Any help or literature recommendations on this topic would be appreciated.
- tom jupille
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The key requirement for LC-MS is that *everything* in the mobile phase must be at least somewhat volatile. To grossly oversimplify, that means use organic rather than inorganic ions. Concentrations typically will be in the 5 - 10 mm range.
-- Tom Jupille
LC Resources / Separation Science Associates
tjupille@lcresources.com
+ 1 (925) 297-5374
LC Resources / Separation Science Associates
tjupille@lcresources.com
+ 1 (925) 297-5374
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As Tom pointed out you are limited in the buffers you can use because of volatility. 0.1% Formic Acid is a typical acidification agent (~pH 3). You can use Ammonium Formate if the target molecule likes pH 7.
DO NOT use TEA (Polysorbate, Tween...) or other compounds that are likely to contaminate you MS source!
DO NOT use TEA (Polysorbate, Tween...) or other compounds that are likely to contaminate you MS source!
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most MS setups are MPA: water with 0.1% formic acid and MPB: as ACN with 0.1% formic acid. This is a good start with a C18 column
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