A study of the adsorption isotherms of Ion-pair reagents

Abstract: In this project, the optimization of obtaining adsorption isotherms for the ion pair reagent, tributylamine was tested. The goal was to have a better understanding of the chromatographic process when separating biomolecules, such as oligonucleotides. To do this one ion pair reagent was tested in different buffers with different compositions of acetonitrile. These solutions adsorbed into a C18 column at different temperatures and stripped into fractions of 35 mL. To analyze the results Liquid-liquid extraction was performed on the fractions and the organic phase was then injected into a gas chromatography. The results showed that at a temperature of 24°C the ion pair reagent adsorbed more to the column than at 37°C and 50°C. For the different compositions of acetonitrile buffers which were tested the one that stood out was the 50% acetonitrile buffert. At all temperature it showed to always be able to adsorb more to the column than the other buffers. To calculate the concentrations of the analytes, standard curves for both tributylamine and dibutylamine were made. For dibutylamine, four unknown samples were provided to test out if the methods could be used to determine the concentrations of dibutylamine in the samples. The methods for acquiring adsorption isotherms and analyzing samples with the gas chromatography showed good results and could be used for more studies. However, to validate the results of the 50% acetonitrile buffer, more work in the future is required.