I need to detect an unknown compound from a marine bacterial extract. I have done general spray tests to preliminary identify the compound and it was positive for alkaloid. In addition, is it compulsory to use of formic as eluent additive for LCMS for the alkaloid?
Thank you :-)
Hi Afifah,
Here's my thought,
Different "purified water" are required for LC-MS, depending on using HPLC or UHPLC with your MS. Depending on what technique you use for water deionization or distillation you will have different quality of water. The result is that deionized water is as pure as the distilled water or even purer. And it is always better to use ultrapurified water in HUPLC, if this is what you intent to use.
Regarding the choice of acid in your analysis, the most acids in LC-MS are formic and trifluoroacetic acid at 0.1% concentrations. The reasons mainly lies at the same time on the nature of your sample and the phase (column) and technique you use. In the LC part, and in particular in the column, ionized silanol groups interact through ion-exchange with ionized bases. You minimize this problem by adding acid to suppress the ionization of the silanol groups. Low pH improve peak shape for both acids and bases compounds, as well as improve retention for acids. In the case of your study, adding acid will may cause ionization of your alkaloids, since they are basic samples, causing a decrease of the retention times, but usually still sufficient
In the case of LC-MS, we commonly use formic acid mainly because it evaporates readily in the MS ionization interface. It also provides sufficient pH control compare to trifluoroacetic acid in the LC part.
In conclusion, formic acid may have an impact on the retention time of your alkaloids, but you will have a better peak shape. It would be better than TFA because of the MS analysis. The choice, to add or not acid in your experiment, is up to you, dependent of the nature of your alkaloids, you may want to know better the type of alkaloids you have by looking for marine bacteria related publications.
I hope I answered your questions, cheers,
Nicolas.
Hi,
It is the best if you use milliQ water, for example as this paper.
https://doi.org/10.1186/s12302-020-00405-7
You have an overview of the method recovery and matrix effect.
I hope this helps!
Hi
Yes, use ultapure water. This paper may helps
https://doi.org/10.1039/C9RA05301H
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