How Triethilamine works on a compound separation in a reversed phase column (C18)?

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.

• Anant Devki Yadav

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 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.

• H. Zulhilmi

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.

• Matthias Balsam

If there is excessive TEA in the mobile phase, it begins to dissolve the silica. When silica dissolves, the bonded functional groups also leave. 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.

• Anonymous

TEA is a basic compound. The excess amount of TEA changes the pH of the mobile phase. At basic condition, TEA exist in its neutral form. Neutral form of TEA will never interact with $SiO^-$. 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.

• H. Zulhilmi