Ion chromatography using anion exchangers modified with heparin

Abstract

Abstract. Retention behavior of inorganic anions and cations on anion exchangers modified with heparin has been investigated. Retention of anions on the anion exchanger was remarkably reduced after the modification with heparin. The cations of the eluent affected the retention behavior of ions. The retention factor of anions decreased with decreasing eluent concentration when sodium sulfate and magnesium sulfate were used as the eluent, whereas it increased with decreasing eluent concentration when aluminium sulfate, copper sulfate and sulfuric acid were used as the eluent. When copper sulfate was used as the eluent, both anions and cations were retained on the modified stationary phase and simultaneous separation of both anions and cations were carried out. Cations as well as non-UV-absorbing anions were indirectly visualized by copper ions. Key words. Ion chromatography -heparin -simultaneous separation of anions and cations.Analusis, 1998, 26, 61-64 © EDP Sciences, Wiley-VCH * Correspondance and reprints. Received January 13, 1998; revised January 13, 1998; accepted January 16, 1998.Article available at http://analusis.edpsciences.org or http://dx.doi.org/10.1051/analusis:1998111 without any further treatment. Purified water was prepared in the laboratory by using a Mill-Q Plus system (Millipore, Molsheim, France). The eluents were prepared using the purified water. Modification with heparinThe IC Anion-SW column was first washed with water at a flow rate of 4.2 µL min -1 for 10 min and with 10 mM sodium sulfate at the same flow rate for 2 h. Aqueous solution of 1.0% heparin was then passed through the column at a flow rate of 4.2 µL min -1 for 2 h, followed by washing with water at the same flow rate for ca. 30 min. Results and discussion Modification with heparinThe expected structure of heparin is illustrated in figure 1. Since heparin has various anionic groups in its unit as in figure 1, it can be introduced into anion exchangers by electrostatic interaction. Since all of the anionic groups do not interact with the anion-exchange sites of the packing, a portion of anionic groups of heparin are remained free and they affect the retention of analyte ions. The repulsion of analyte anions from the modified surface may depend on the pH and the ionic strength of the eluent.The mass distribution of heparin employed in this work is illustrated in figure 2. From the size-exclusion chromatography data, the weight-average molecular weight of heparin employed was calculated to be 2.2 × 10 4 by using poly(ethyleneoxide) (PEO) as the standard, whereas the molecular weight of PEO completely excluded from the pore of the IC-Anion-SW packing is (5 -6) × 10 4 . From these estimations, it is presumed that heparin can enter the pore of the packing to some depth depending on the size and a portion of the inner part of the packing is remained unmodified. In other words, the modified packing possesses both negative charges due to free anionic groups of heparin and positive charges due to the original bare anion-exchange sites....

Capillary ion chromatography

“…They followed up this work with heparin-coated columns [53]. Like chondroitin, heparin contains an amidosulfonic acid group aside from carboxylate and sulfonate groups.…”

Separation of Inorganic Anions Using Methacrylate-Based Monolithic Column Modified with Trimethylamine in Ion Chromatography Capillary System

“…[2,3] developed bovine serum albumin as a stationary phase for the separation of inorganic anions. A few papers also have been reported for the simultaneous separation of anions and cations [4][5][6].…”

Ion chromatography using anion-exchangers modified with dextran sulfate

“…There is another modification method that controls the ion-exchange capacity, e. g., electrostatic modification. The authors found that silica-based anion-exchange columns could be modified by coating with anionic mucopolysaccharides such as chondroitin sulfate and heparin [5][6][7]. It was observed that the modified columns exhibited unusual retention behavior owing to the presence of free anionic groups of the modifier as well as residual anion-exchange sites of the substrate.…”

“…Strongly basic anion-exchangers modified with heparin retained both anions and cations, and simultaneous separations of anions and cations were demonstrated using copper sulfate as eluent [6]. It was suggested that the modifier size would strongly affect the ion-exchange properties of the modified phase.…”