triethylamine (TEA) is usefull when you're handling conventional C18 column where the silica backbone contains free silanol group Si-OH. When this silanol ionized into Si-O(minus), it produces ionic retention mechanism where positive molecule species will be attracted and retain longer on the column bed (which is good basically). there some cases where the interaction of ionized silanol with some molecules especially pharmaceutical compound (they contain a lot of amine, NH2 group) is strong to an extent where this interaction produces a hideous tailing chromatogram peak. So, this is when the use of TEA is appropriate. TEA temporarily interact with ionized silanol group at higher affinity to so that other compound cannot interact with that silanols. In other word, it protects or deactivates the silanol from interacting with your compounds. to totally inhibit silanol activity, 10 mM of TEA would be enough but i recommend that you optimized the amount of TEA (just enough to prevent peak tailing) to add an extra ionic retention mechanism on your column (not just reversed phase mechanism). if you dont want any silanol activity, just purchase end capped HPLC column where it deactivates silanol group by adding a permanent covalent alkyl linkage with that silanol (Si-O-R). with these column, TEA will not be needed.

Hi Carlos,

triethylamin is a quaternary amine, which is positive charge. The "nonpolar" ethyl groups interacted with the nonpolar C18 groups of your colmn. Due to that the positive charged amine group, the surface of you nonpolar C18 column get more polar and your analyte can interact with his polar functionally groups.

Does that answer your question???

Regards Matthias

triethylamine (TEA) is usefull when you're handling conventional C18 column where the silica backbone contains free silanol group Si-OH. When this silanol ionized into Si-O(minus), it produces ionic retention mechanism where positive molecule species will be attracted and retain longer on the column bed (which is good basically). there some cases where the interaction of ionized silanol with some molecules especially pharmaceutical compound (they contain a lot of amine, NH2 group) is strong to an extent where this interaction produces a hideous tailing chromatogram peak. So, this is when the use of TEA is appropriate. TEA temporarily interact with ionized silanol group at higher affinity to so that other compound cannot interact with that silanols. In other word, it protects or deactivates the silanol from interacting with your compounds. to totally inhibit silanol activity, 10 mM of TEA would be enough but i recommend that you optimized the amount of TEA (just enough to prevent peak tailing) to add an extra ionic retention mechanism on your column (not just reversed phase mechanism). if you dont want any silanol activity, just purchase end capped HPLC column where it deactivates silanol group by adding a permanent covalent alkyl linkage with that silanol (Si-O-R). with these column, TEA will not be needed.

Ok. I think I understand the mechanism of action of TEA.

So, one more question. What happens with the tailing effect with an excess of TEA. The last day i was working and my colleagues make a mistake during Mobile phase preparation and an excees of TEA was added to the aqueous solution. The result of this was an increase of the retention time of the analyte and a very significative effect on the tailling...a very large tail appear after the elution of the compound. This sounds contradictory with the objective of the use of TEA for prevent tailling...

My speculation would be;

The excess amount of TEA changes the pH of your mobile phase.

As we know, TEA is a basic compound. at basic condition, TEA exist in its neutral form. neutral form of TEA will never interact with Si-O(minus). furthermore, at basic condition all silanol definitely will exist in its ionic form (all of them) which may cause longer peak retention on your case. Unless you adjust the pH of your mobile phase into acidic mobile phase after the addition of TEA, that's not going to be a problem.

If you already change the pH of your mobile phase after the addition of TEA and the problem still persist, there might be another problem.

maybe you can tell what is your analyte for your study.

Ok. So my analyte is CASPOFUNGIN. When I get advised about the mistake was made, I prepare the mobile phase with the right composition of components and reinject the same vial samples and the retention time and form of the peak was restored (I was worried about my column).

Mi mobil phase is composed by a 35% of Acetonitrile and 65% of acqueous solution with trifluoroacetic acid at 0.1% and alcalinized with TEA up to pH 3.0.

Thank you very much.

Amines are notorious for sticking to chromatography columns. This happens when they stick to charged sites on the column. If you sample is an amine then you might have that problem. TEA is also an amine so when you add it to your mobile phase it sticks to the charged sites in on the column and blocks you sample from sticking to most of them.

TEA is also a base, so it can be used to increase the pH of your mobile phase, and it is volatile, so most of it can be evaporated off after the separation.

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Triethylamine is used to mask free silanol groups on the HPLC column and therefore it improves peak shape of the analytes.

Moreover it can be used to increase/adjust the pH of the mobile phase and serve both the purpose of pH adjustment and peak shape improvement.

It is also known to increase the retention time in case of acidic analytes.