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- Ammonium Formate vs. Ammonium Acetate in HILIC
There are three considerations here: 1) An unbuffered acid tends to be a chaotrope, and chaotropes antagonize retention in HILIC If you're at a pH above the pKa of the anion (3 75 for formate and 4 75 for acetate), then this won't be an issue If you're at a pH well below the pKa, then a lot of the anion will be in the unbuffered acid form
- A Guide to HPLC and LC-MS Buffer Selection
work, phosphate, cannot be used Ammonium acetate is sufficiently volatile for LC-MS use, but we are left with the 2 0<pH<3 8 and 5 8<pH<8 0 range to cover Table 2 lists several additional buffers that are sufficiently volatile for LC-MS use Ammonium formate (2 7<pH<3 7) does a fairly good job of filling buffer pH range LC-MS compatible
- Buffers and Eluent Additives for HPLC Method Development
Compare this to the use of ammonium acetate or formate buffers at low pH where the buffering ranges of the ammonium species and the format or acetate are several pH units apart (see Table 1) Under these circumstances, the ammonium ion is merely acting as an MS friendly counter ion in place of sodium or phosphorous ions
- Buffer Considerations for LC and LC–MS - Chromatography Online
MS-Friendly Buffer Mixtures: Ammonium Carbonate, Acetate, and Formate Buffers composed of two buffering species are used commonly in HPLC systems In particular, ammonium formate, ammonium acetate, and ammonium carbonate are used widely when HPLC is coupled to mass spectrometry (MS)
- Making LC Methods MS Friendly - Agilent
•Ammonium salts (ammonium formate and ammonium acetate) favor formation of ammonium adducts •TFA causes ion suppression •Use TFA “fix” – post column addition of acetic or propionic acid •Basic mobile phases generally favor negative mode ionization •Ammonium hydroxide, triethylamine, diethylamine, piperidine, ammonium bicarbonate
- Impact of Mobile Phase Additives on LC-MS Sensitivity, Demonstrated . . .
Using the socially problematic spice cannabinoids as the test case, the study reported here demonstrates the impact of various mobile phase modifiers on the separation, with the formate modifiers outperforming acetate in terms of MS signals (or sensitivity) and chromatographic resolution
- Chrominfo: LC-MS compatible buffers
Ammonium acetate (pKa-9 2) Ammonia (NH4OH) (pKa-9 8) The buffer is more effective when used in ± 1 pH unit of its pKa, however adequate buffering from the pKa can provide the ± 2 pH unit
- format or acetate - Chromatography Forum
In general, you will be better off in MS applications to just use formic acid, instead of ammonium formate buffer, but this may create tailing peaks under many circumstances So the use of formic acid versus ammonium formate buffer is a trade-off of MS response versus good chromatography
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