Hyperbranched anion exchangers prepared from polyethylene polyamine modified polymeric substrates for ion chromatography

High hydrophilic anion stationary phases play a crucial role in the separation behavior of ion chromatography. Herein, we report novel polymeric anion exchangers grafted with polyethylene polyamines, including ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylene pentaamine, via a facile epoxy-amine polymerization method. The anion exchangers were characterized by scanning electron microscopy, thermogravimetry, Fourier transform infrared spectrometry and elemental analysis. The chromatographic performance of the stationary phases was evaluated with the separation of common inorganic anions, organic weak acids and highly polarizable anions. Seven common anions (F − , Cl − , NO 2 − , Br − , NO 3 − , SO 4 2− and HPO 4 2− ) can be separated within 18 min by using hydroxide eluent in isocratic mode. By adopting different polyethylene polyamines as hyperbranched units, the four types of new stationary phases displayed high efficiencies and good reproducibility. The columns exhibit large exchange capacities at 76.5–184.8 μmol•column −1 (4.6 × 150 mm, i.d.) with efficiency up to 20293 plate m −1 (Cl − ). The RSDs of the retention time were less than 0.27% and the RSDs of the efficiency were less than 1.95% by consecutive injections after working for two months. The self-fabricated column was successfully applied to determine the chloride content in exhaled breath condensate.