Latexed Cation Exchangers

The separator column introduced as the Fast-Sep-Cation has similar physical properties. This column was developed primarily for the fast separation of alkali or alkaline-earth metals. In combination with a column switching technique, it is also suitable for the simultaneous analysis of the most important cations of both compound classes (see 

Section 3.4.4). The dimensions of the Fast-Sep-Cation column are 250 mm x 4 mm I.D. Compared to the CS3 column, the 13-pm particle diameter of the substrate is slightly higher. The sulfonated latex beads are crosslinked with 4% DVB and have a diameter of about 225 nm. 

250 nm and a degree of cross-linking of 5 %. In contemporary practice, such a 

The separator column introduced as the Fast-Sep Cation has similar physical properties. This column was developed primarily for the fast separation of alkali-or alkaline-earth metals. In combination with a column-switching technique, it is also suitable for the simultaneous analysis of mono- and di-valent cations (see Section 4.4). However, in terms of separation power and peak efficiencies, the separations obtained in this way are inferior to those obtained with carboxylate-based weak acid cation exchangers (described in Section 4.1.1). The dimensions of the Fast-Sep Cation column are 250 mm X 4 mm i.d. The 13-pm particle diameter of the substrate is slightly higher than that of the CS3 column. The sulfonated latex beads are cross-linked with 4% DVB and have a diameter of about 225 nm. 

The analysis of amines is an application area of great significance [8], As an important object of recent application developments, for example. Fig. 4-28 shows the isocratic elution of monovalent cations and ethanolamines on lonPac CSll, the microbore version of the lonPac CSIO with a slightly higher ion-exchange capacity. Under the chromatographic conditions used, a baseline-resolved separation of mono-, di-, and tri-ethanolamine as well as N-methyldietha-nolamine is achieved within 30 minutes. 

Another important application for the lonPac CSIO is the separation of biologically relevant amines such as choline and acetylcholine, which previously have been used to be separated by ion-pair chromatography (see Section 6.4). 

Cation exchange chromatography with a methanesulfonic acid eluant is a much simpler alternative. For optimizing peak efficiencies, 1 % (v/v) methanol is added to the mobile phase. As an alternative to the lonPac CSIO, an OmniPac PCX-100 (see Section 6.7) can also be used. The latter one has very similar separation properties, but it is characterized by a lower hydrophobicity of the cation exchange functionality, which improves peak efficiency for choline and its derivatives even more. 

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Fig. 3-132. Separation of alkali metals on a latex cation exchanger. - Separator column Fast-Sep Cation I chromatographic conditions see Fig. 3-129.

Fig. 3-140. Separation of monoethylamine, di-ethylamine, and triethylamine on a latex cation exchanger. - Separator column IonPac CS3 eluent 0.04 mol/L HC1 flow rate 1 mL/min detection suppressed conductivity injection volume 50 pL solute concentrations 20 ppm monoethylamine, 50 ppm diethylamine, and 100 ppm triethylamine.

Fig. 4-17. Separation of some early eluting amino adds on a latex cation exchanger such as AminoPac PC-1. — Eluent i 0.0002S mol/L HN03 flow rate 1 mL/min detection fluor-...

The eluents suitable for the separation of amino acids on latex cation exchangers do not comprise the classical citrate/borate buffers but mixtures of nitric acid and potassium oxalate. In comparison to buffers composed of sodium citrate and borate, these components may be obtained at much higher purity. The retention of the amino acids to be analyzed, however, is possibly affected by the sample pH due to the limited buffer capacity of the eluents that are based on nitric acid and potassium oxalate. Fig. 4-21 shows the separation of a calibration standard for collagen hydrolysates on an Amino Pac PA-1 latex cation exchanger at ambient temperature. The advantage is the short... 

Cation exchangers are usually made of organic polymers (styrene-divinylbenzene, ethylvinylbenzene-diviniylbenzene, polymethacrylate, and polyvinyl), however, a variety of other substrate materials are also available (e.g., latexed cation exchangers, sUica-based exchangers). 

Latex cation exchangers were introduced by Dionex Corp. 10 years later than latex-agglomerated anion exchangers. These types of cation exchangers consist of a weakly sulfonated PS-DVB substrate with latex beads with a very small diameter agglomerated on its surface by both electrostatic and van der Waals interactions. 

In contrast to surface-sulfonated phases, latex cation exchangers exhibit a significantly higher chromatographic efficiency. Examples of Dionex latex cation-exchange columns are given in Table 9. 

Table 9 Selected columns of latexed cation exchangers.

Fig. 4-24. Schematic representation of a latexed cation exchange particle.

Fig. 4-56. Separation of transition metals on the lonPac CS5A bifunctional latexed cation exchanger. - Eluant ...

Alternatively, uranyl cations can also be separated on an lonPac CS3 latexed cation exchanger utilizing a buffer mixture of ammonium sulfate and sulfuric acid as an eluant. Detection is performed as it is for transition metals, via derivatization with PAR. 

Fig. 4-59. Separation of aluminum on a latexed cation exchanger. -Separator column lonPac CS3 eluant 0.2 mol/L (NH4)2S04 + 0.01 mol/L H2SO4 flow rate 1 mL/mln detection photometry at 313 nm after derivatization with Tiron injection volume 50 jL solute concentration ...

The corresponding AminoPac PA-1 latexed anion exchanger, introduced at the same time as the AminoPac PC-1, has been replaced meanwhile by a more modern product, the AminoPac PA-10 (see Section 3.11). The baseline-resolved separation of 17 amino acids contained in a hydrolysate standard requires about 40 minutes, which is significantly longer than with a latex cation exchanger. 

Fig. 7-22. Pulse sequence for integrated amperometry of ethanolamines and their separation on a latexed cation exchanger. — Separator lonPac CSIO eluant ...

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