For the mass analysis of small organic molecules, especially bioactive compounds, which ionization technique is best in Liquid Chromatography Mass Spectrometry (LC-MS)? It is evident that most of the literature is dominated by ESI based LC-MS.
Hi, ESI is preferrable as MALDI is preferable for large molecular weight samples like proteins.
If hyphenating LC with MS something like ESI or APCI etc will be much easier as these can be directly coupled in an online mode.
While you *can* do LC-MALDI you would really have to want to... Spotting fractions of effluent onto MALDI plates, and the taking the plates to the MS is much more challenging than just running the outlet of your column directly into a MS. Many more chances for losses, errors, and a lot more work which is generally not worth it, though I am sure some here can give good examples of when you would want to do LC-MALDI.
Hello, It always depends on your downstream application. Why do you want to "pass" your sample through MS. Is it fragmentation and identification that you are after, is it just mass screening, do you opt for some kind of quantification? Is your sample too complicated that needs separation prior to MS detection?
To cut the long story...MALDI has been used to screen for small molecules and some efforts were pointing that way but most of them just for research purposes. The majority of practical applications is focused towards LC-ESI-MS and MS/MS.
Hope this helps
I recommend reading the attached file. A good alternative for those who do not have an ESI, but has a Maldi.
Hi! ESI source is definitively the best choice between the two, especially if you are interested in using also LC. As others have already explained the coupling LC-MALDI is extremely challenging. In addition MALDI is more suitable for larger molecules such as proteins and polymers, whereas in the case of small ones you likely have noise due to the matrix.
Hi. MALDI is essentially performed for protemics analysis. It's adapted for large molecules like proteins or polymers. For small molecules preferred ESI. Electrospray is the universal source for small molecules like pesticides, toxins, pharmaceuticals especially if LC is used for separation. And depends on your molecules you can also use APCI (atmospheric pressure chemical ionization). But it also depend on the material you have in your laboratory. I hope this answer help you in your analysis.
For qualitative work, Eeither should work but the MALDI suffers from the matrix effects. If you want to do quantitative analysis, ESI is a better choice.
"Hi! ESI source is definitively the best choice between the two, especially if you are interested in using also LC."
If you are not interested in HPLC/UHPLC (or if you don't really need separation), you can introduce your sample to ESI source by
direct injection using a syringe pump. Quick and easy!
Either will work, but MALDI is more forgiving if you are using lipids. But how small is small? Masses
I will likely offend some of you, and may come across as arrogant but so be it. Someone should try to keep the masses on track.
Many people make very good points in the debate of whether to use MALDI or LC-ESI here. However, the original question was which is better to couple to LC... Which makes many comments about MALDI meaningless in the context of the question.
Please read the poster's question and answer their question. If the question isn't clear, ask for more details. If you do not have a better answer than one that is already posted or something new to add, just vote the answers that you agree with up. This way you don't waste your time or anyone else's.
Hi james,
have you heard of an LC-MALDI? I use one routinely, but they are not cheap as a robotic spotter is required additional to the LC (nanoLC also) & MALDI. Then your results are preserved for off line investigation; and re-investigation.
Yup, my colleague downstairs has built these systems. It can be done, but you would have to have a good reason to do LC-MALDI because the hyphenation is not so simple (as you point out).
It is nice if you want to go back to your plates later on to analyze them again, providing that you can store the plates without losing the analytes.
Sincerely, ESI is more appropriated than MALDI. For example, you don´t need use any matrix by ESI. Depend on the kind of molecule you should use a specific matrix by MALDI.
for matrices like coffee you can use ESI source by
direct injection using a syringe pump. Quick and easy qualitative analises!
I have experience only in ESI and APCI. Both gave me good answers to my projects.
See Org. biomol. chem. 2013,11, 5069.
I have esperience with ESI and APCI. both gave me good anwers. See
Org. Biom. Chem. 2013, 11, 5069.
The optimum ionization method depends on the nature of the compunds to be detected. ESI is best for polar and charged compounds. APCI is generally better for small molecules, but APPI may be even better in some instances. LC/MALDI is a special case. You need to have a suitable analytical problem to use LC/MALDI as the method of choice.
For low molecular weight organic molecules, ESI-MS is more suitable than MALDI. Beacause in MALDI, matrix peaks will be dominated in low mass range. So it will be very difficult to identify the target compounds from the matrix peaks. The analysis also depends on the nature of the target molecules. If you are looking for polar molecules ESI teechnique is a better option and for non polar compounds APCI technique is a better option. Hope, this information will help you.
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