You can use acid-base titration with HCl to determine the total amount of amines and piperazines in your sample mixture. Dissolve the sample in water, titrate with standardized HCl, and monitor the pH. The first equivalence point will indicate the neutralization of piperazine and tertiary amine groups, allowing you to calculate the total moles of these basic functional groups. Ensure the use of a standardized HCl solution and careful pH monitoring to achieve accurate results.

Abdelhak Maghchiche Thanks for your answer, Actually I did the same but so much acid was used about 400 ml. The first equivalent point is pH around 7. And it will be the total moles, is it possible to know only MDEA (Tertiary amine)?

The acid-base titration method using HCl cannot differentiate between tertiary amines and other basic functional groups like piperazines in a complex mixture, resulting in a large volume of HCl being consumed and the first equivalence point occurring around pH 7, representing the total moles of all basic groups; to determine the amount of a specific tertiary amine like MDEA alone, more selective analytical techniques are required, such as back-titration, chromatographic separation (HPLC or GC), or spectroscopic methods exploiting the unique UV absorption or NMR signal of MDEA, which can provide a quantitative assay for the target analyte.

Thanks for the answer, yes I think UV-VIS or Raman spectroscopy will be good. but I do not have these instruments now. Can you please guide me more on back tiration? thanks, Abdelhak Maghchiche

The back-titration technique involves the following steps:

1. Reaction with Excess Acid

Add a known excess amount of a strong acid, such as hydrochloric acid (HCl), to your sample containing the tertiary amine.

The tertiary amine will react with the excess acid, consuming a portion of the added acid.

2. Back-Titration of Unreacted Acid

Titrate the remaining unreacted acid in the solution with a standard base solution, such as sodium hydroxide (NaOH).

The volume of base required to neutralize the unreacted acid can be used to calculate the amount of tertiary amine present.

Calculation

Let's say the initial amount of HCl added was x moles and the amount of NaOH required to neutralize the unreacted acid was y moles.

The amount of HCl consumed by the tertiary amine = x - y moles

Since the reaction between the tertiary amine and HCl is a 1:1 stoichiometry, the amount of tertiary amine present = x - y moles.

This back-titration approach allows you to selectively quantify the tertiary amine of interest, even in a complex mixture, without interference from other basic functional groups.

This sounds good, I will give it a try. Thanks a lot for the information.