Dear to whom it may concern,
I would like to kindly ask you about the ionization of acidic and salty forms of a given compound in electrospray ionization.
To be more specific, when I successively infused the reference standard solutions of atorvastatin in both its acidic (atorvastatin with an exact mass of 558.25) and salty (atorvastatin calcium with an exact mass of 1154.45) forms into the ionization source (electrospray ionization known as ESI) of the mass spectrometer, I always obtained the same precursor ion (m/z 559.5 in positive mode) of its forms.
I do not understand the reason why the atorvastatin calcium could show the same precursor ion as that of the acidic form of atorvastatin.
May you please give me an explanation of how the salty form of atorvastatin is ionized in ESI, resulting in the same precursor ion as that of the acidic form of atorvastatin?
Thank you so much.
Best regards,
Hello
in solution salts tend to dissociate, so the calcium separates from the Atorvastatin molecule so you can obtain only the mass of the free Atorvastatin.
regards.
Hello Luca Narduzzi,
Thank you so much for your response.
As you said that in solution, the salty will dissociate to form cation Ca2+ and anion atorvastatin (not the neutral form of atorvastatin). Hence, I wonder how the anion form of atorvastatin can be converted into the neutral form of atorvastatin if the solution is not acidic aqueous solution but organic solvent such as acetonitrile.
To my understanding, acetonitrile, methanol, isopropoanol etc. act as electron donors in ESI conditions, enhancing ionization in ESI+. This is one of the reason why ionization in ESI+ is enhanced by solvents (the other is their faster vaporization than water in ESI conditions).
some solvents are better electron donors than others, and you may notice signal enhancement switching from one to another...
hope this helps...
- Badges
- Science topic
- Similar topics
- Phytochemistry
- Extracts