Covalently grafted anion exchangers with linear epoxy-amine functionalities for high-performance ion chromatography

Hybrid grafted and hyperbranched anion exchangers for ion chromatography

Novel grafted anion exchangers with covalently bonded hyperbranched functional layers were prepared and evaluated for the separation of monovalent standard inorganic anions and oxyhalides. Preparation of base coating included grafting highly polar N-vinylformamide to the ethylvinylbenzene-divinylbenzene (EVB-DVB) substrate surface in highly polar solvent (methanol) with subsequent hydrolysis of grafted amide polymer in basic media, which resulted in preparation of polymer chains with multiple primary amino groups. Those amino groups were used as attachment points for forming hyperbranched anion-exchange layers using 1,4-butanediol diglycidyl ether and primary mono- or diamine (methylamine or 1,3-diaminopropane, respectively). The effects of hyperbranching reaction cycles number on selectivity were evaluated which revealed that selectivity and capacity can be controlled independently for the covalently bonded stationary phases in contrast to electrostatically bonded phases. It was demonstrated that unlike for electrostatically bonded phases, the intentional increase of crosslink by using primary diamine instead of primary monoamine doesn't cause the shift of selectivity coefficients. It was also shown that crosslink distribution throughout the hyperbranched layer is an important factor determining selectivity of hyperbranched anion exchangers.

Polyelectrolyte-grafted anion exchangers with hydrophilic intermediate layers for ion chromatography

The hydrophobicity of polymer-based anion exchangers is a persistent problem in suppressed anionic chromatography (SAC) due to its adverse effect on chromatographic performance. Herein we describe polyelectrolyte-grafted anion exchangers with modified hydrophilic intermediate layers. The anion exchangers were functionalized by successively grafting a linear cationic condensation polymer (LCCP), a preprepared polyelectrolyte. The carboxylic/hydroxylic intermediate layers formed during thiol-radical-mediated polymerization exert distinct effects on the phase capacity and hydrophobicity. The separation of typical inorganic anions, polarizable anions, and organic acids shows that the anion exchangers display good performance in SAC mode.

Dendrimer-functionalized hydrothermal nanosized carbonaceous spheres as superior anion exchangers for ion chromatographic separation

Polyamidamine (PAMAM) dendrimer-functionalized hydrothermal nanosized carbonaceous spheres (HNCSs) were prepared and utilized as latexes for agglomerated anion exchange chromatography (AEC) stationary phase. The high-concentration and scalable production of monodisperse HNCSs (73-98 nm) was accomplished via the polyquaternium-7-assisted hydrothermal carbonization of fructose. The novel PAMAM-based quaternizations of HNCSs were designed by the amidation with PAMAM and epoxy-amine addition reaction with glycidol in aqueous solution. The mild functionalization condition leads to well-kept morphology of HNCSs, which forms one even latex layer on the sulfonated surface of polystyrene-divinylbenzene microbeads for the construction of AEC packing. Under isocratic elution, seven common inorganic anions and five organic acids were baseline separated in 9 min on prepared packing with efficiencies of 54,000-79,800 plates m^-1 and asymmetry factor (As) of 1.02-1.12. The obtained separation efficiency, peak symmetry, and analysis time were superior to reported or typical commercial counterparts. The quick separation of polarizable anions in 7 min and carbohydrates in 5 min could also be carried out with symmetrical peaks (As: 1.00-1.18) and high efficiencies (49,700-62,100 N/m). Favorable stability and reproducibility were proved by continuous flushing and injection. The constructed packings were further applied to the determination of thiosulfate and sulfate in water reducer, galacturonic acid in Angelica polysaccharide hydrolysate, and fluoride samples in 4 min.

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^-, NO₂^-, Br^-, NO₃^-, SO₄^2- and HPO₄^2-) 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.

A review of the design of packing materials for ion chromatography

The development of ion chromatography has made remarkable progress in the past few decades, and it is now widely used for the analysis of common ions and organic compounds. Ion chromatography has many advantages, such as fast, high sensitivity, good selectivity and support for simultaneous analysis of multiple ionic compounds. In order to meet the high requirements of material analysis, new packing materials for ion chromatography with higher sensitivity and selectivity have been developed. In this paper, a lot of knowledge of ion chromatography is reviewed, and the development of ion chromatographic packings in recent years, especially in the last five years, is summarized.