Preparation of poly(glycidylmethacrylate-divinylbenzene) weak acid cation exchange stationary phases with succinic anhydride, phthalic anhydride, and maleic anhydride for ion chromatography

Preparation and Application of Weak Cation Exchange Resin Based on Thiol Click Reaction

Using poly(styrene-divinylbenzene) microspheres as stationary phase matrix and mercaptosuccinic acid as a modifier, a new weak cation exchange resin was synthesized by thiol click reaction. The conditions for thiol-chlorine click reaction and thiol-alkene click reaction were optimized. The surface morphology and chemical composition of the modified microspheres were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and an elemental analyzer. The stationary phase can achieve the separation of six common cations within 25 min. A homemade weak cation chromatographic column was used to determine the impurities of Na+ and K+ and the content of tetramethylammonium ions in tetramethylammonium hydroxide samples. The method showed a good linear correlation in the range of 0.1-500.0 mg/L with correlation coefficients of 0.9998-0.9999, and the limits of detection (signal-to-noise ratio ≥ 3) were 0.01-0.20 mg/L. The intra-day relative standard deviations (RSDs) were in the range of 1.1%-4.4%, and the inter-day RSDs were in the range of 0.8%-14.8%. The spiked recoveries were in the range of 91.92%-119.86%. The results showed that the prepared stationary phase exhibited effective separation ability and good reproducibility, which was suitable for the analysis of the impurities of Na+, K+, and the content of tetramethylammonium in the tetramethylammonium reagents.

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.

Preparation of a polymer-based weak cation exchanger for ion chromatography via atom transfer radical polymerization

A novel polymer-based weak cation exchanger (WCX) for ion chromatography has been described. It was prepared by grafting tert-butyl acrylate and maleic anhydride onto the surface of poly(glycidyl methacrylate-divinylbenzene) microspheres via atom transfer radical polymerization, followed by hydrolytic treatment to produce acrylic and maleic acid groups. The obtained WCX showed better separation and higher selectivity for model cations relative to solely acrylic or maleic acid. Simultaneous separation of alkali and alkaline earth cations (including NH₄⁺) was achieved in a single isocratic run under suppressed mode, and ion exchange was found to dominate the separation process. Its utility was demonstrated for determination of several cations in a beer sample and the recovery was ranging from 98.4 to 109.9%.

Studies on Preparation, Characterization and Application of Porous Functionalized Glycidyl Methacrylate-Based Microspheres

A one-step swelling and polymerization technique was used in the synthesis of porous glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) monodisperse polymeric microspheres. The polystyrene (PS) seed obtained in the dispersion polymerization was used as a shape template. The presence of epoxide rings in the chemical structure of microspheres enables their post-polymerization chemical modifications involving: the Diels-Alder reaction with sodium cyclopentadienide and maleic anhydride, the reaction with 4,4′-(bismaleimido)diphenylmethane, and the thiol-Michael reaction with methacryloyl chloride and 2-mercaptopropionic acid. Changing the reaction mixture composition—the amounts of crosslinking monomer and PS seed as well as the type and concentration of porogen porous microspheres of different porous structures were obtained. Their porous structures were characterized in the dry and swollen states. The copolymers obtained from the equimolar monomers mixture modified in the above way were applied as the column packing materials and tested in the reverse-phase HPLC (High-Performance Liquid Chromatography). A few factors influencing morphology and porous structure of microspheres were studied.

Utilization of Anion-exchange Guard Column as an Ion Chromatographic Column of Anions Including Application to Simultaneous Separation of Anions and Cations

This study demonstrated that a guard column containing anion-exchange resin has the potential for use as a separation column for acid eluent. Specifically, a 1-cm long anion-exchange guard column with a 4.6-mm internal diameter provided good separation of monovalent inorganic anions, by elution of 8 mM tartaric acid or 4 mM malic acid. Using the guard column with acid eluent could be applied to evaluation of nitrite and nitrate ions in mountain and urban river water samples. When the guard column was connected in front of a cation-exchange separation column (15 cm long × 4.6 mm internal diameter) in a series, the system provided simultaneous separation of anions and cations in eluent of 8 mM tartaric acid and 0.5 mM 18-crown-6 ether by a single injection.

Recent developments in capillary and microchip electroseparations of peptides (2015-mid 2017)

The review brings a comprehensive overview of recent developments and applications of high performance capillary and microchip electroseparation methods (zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography) to analysis, microscale isolation, purification, and physicochemical and biochemical characterization of peptides in the years 2015, 2016, and ca. up to the middle of 2017. Advances in the investigation of electromigration properties of peptides and in the methodology of their analysis (sample preseparation, preconcentration and derivatization, adsorption suppression and EOF control, and detection) are described. New developments in particular CE and CEC methods are presented and several types of their applications to peptide analysis are reported: qualitative and quantitative analysis, determination in complex (bio)matrices, monitoring of chemical and enzymatical reactions and physical changes, amino acid, sequence and chiral analysis, and peptide mapping of proteins. Some micropreparative peptide separations are shown and capabilities of CE and CEC methods to provide important physicochemical characteristics of peptides are demonstrated.

Simple determination of betaine, l-carnitine and choline in human urine using self-packed column and column-switching ion chromatography with nonsuppressed conductivity detection

A sequential online extraction, clean-up and separation system for the determination of betaine, l-carnitine and choline in human urine using column-switching ion chromatography with nonsuppressed conductivity detection was developed in this work. A self-packed pretreatment column (50 × 4.6 mm, i.d.) was used for the extraction and clean-up of betaine, l-carnitine and choline. The separation was achieved using self-packed cationic exchange column (150 × 4.6 mm, i.d.), followed by nonsuppressed conductivity detection. Under optimized experimental conditions, the developed method presented good analytical performance, with excellent linearity in the range of 0.60-100 μg mL^-1 for betaine, 0.75-100 μg mL^-1 for l-carnitine and 0.50-100 μg mL^-1 for choline, with all correlation coefficients (R² ) >0.99 in urine. The limits of detection were 0.15 μg mL^-1 for betaine, 0.20 μg mL^-1 for l-carnitine and 0.09 μg mL^-1 for choline. The intra- and inter-day accuracy and precision for all quality controls were within ±10.32 and ±9.05%, respectively. Satisfactory recovery was observed between 92.8 and 102.0%. The validated method was successfully applied to the detection of urinary samples from 10 healthy people. The values detected in human urine using the proposed method showed good agreement with the measurement reported previously.