Comparing the separation performance of poly(ethyleneimine) embedded butyric and octanoic acid based chromatographic stationary phases

Poly(ethyleneimine) (PEI) modified silica spheres were used to graft butyric acid and octanoic acid onto their surfaces, forming two stationary phases named Sil-PEI-BAD and Sil-PEI-CAD, respectively. Characterized methods including fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA) and thermogravimetric analysis (TGA) were utilized to determine the successful synthesis of these two stationary phase materials. The chromatographic performance of these two stationary phases was analyzed with hydrophobic and hydrophilic compounds as analytes. Compared with Sil-PEI-CAD column, Sil-PEI-BAD column was more effective in separating hydrophilic compounds including nucleosides, alkaloids and vitamins. Hydrophobic substances including polycyclic aromatic hydrocarbons (PAHs) and alkylbenzenes obtained excellent separation results on Sil-PEI-CAD column than Sil-PEI-BAD column. Additionally, according to the separation of phenols, Sil-PEI-CAD column can be used in HILIC/RPLC mixed-mode. The results showed that the properties and retention mechanisms of the prepared stationary phases depended on the length of the alkyl chains bonded on the silica surface.