Strong cation exchange packings

Figure 4. Standards recovered from 10 mL of distilled-deionized water on a strong-cation-exchanger packed precolumn. Peak identities 4, 0.14 pg of caffeine 5,0.20 pg of pentachlorophenol 6y 0.42 pg of aniline 7,0.061 pg of m-nitroaniline 8, 0.15 pg of atrazine 9, 0.40 pg of quinoline 10, 0.26 pg of 2,6-dichloroaniline 11,0.14 pg of N-nitrosodiphenylamine and 12,0.055 pg of pyrene. Conditions for concentration, analytical separation, mobile-phase gradient, and detection were the same as in Figure 3. Reproduced with permission from reference 18.)...

Rodgers used a pellicular strong cation-exchange packing for the separation of some Rau-woifia alkaloids. An ammonium phosphate buffer (pH 7.0) containing methanol was used as eluent. An improved separation was obtained with gradient elution. 

Column. 15.0 cm x 4.6 mm, packed with a 5/on silica SCX (strong cation exchanger) bonded phase. 

The polyamines putrescine, cadaverine, spermidine, and spermine, which are seen at elevated levels in some victims of cancer, were separated on a Technicon (The Technicon Company Chauncey, NY) TSM Amino Acid Analyzer packed with an 8% divinylbenzene-co-polystyrene sulfonated resin with post-column ninhydrin detection.111 Amines such as ethanolamine, noradrenaline, hexamethylene diamine, methoxytryptamine, spermine, and spermidine were separated from amino acids on a DC-4A cation exchange resin.112 A similar approach, using a Beckman Model 121M amino acid analyzer equipped with an AA-20 column, was also successful.113 A Polyamin-pak strong cation exchange column (JASCO) was eluted with a citrate buffer for the detection of putrescene, spermine, cadaverine, and 1,5-diaminohex-ane from rat thymus.114 A post-column o-phthaldehyde detection system was used. 

The application of polymer monoliths in 2D separations, however, is very attractive in that polymer-based packing materials can provide a high performance, chemically stable stationary phase, and better recovery of biological molecules, namely proteins and peptides, even in comparison with C18 phases on silica particles with wide mesopores (Tanaka et al., 1990). Microchip fabrication for 2D HPLC has been disclosed in a recent patent, based on polymer monoliths (Corso et al., 2003). This separation system consists of stacked separation blocks, namely, the first block for ion exchange (strong cation exchange) and the second block for reversed-phase separation. This layered separation chip device also contains an electrospray interface microfabricated on chip (a polymer monolith/... 

Chromatographic System Use a liquid chromatograph equipped with a refractive index detector that is maintained at a constant temperature and a 9-mm x 30-cm column packed with a strong cation-exchange resin, about 9 pm in diameter, consisting of sulfonated cross-linked styrene-divinylbenzene copolymer in the calcium form (Aminex HPX-87c, or equivalent). Maintain the column temperature at 85° + 0.5°, and the flow rate of the Mobile Phase at about 0.5 mL/min. Chromatograph the Standard Preparation, and record the peak responses as directed under Procedure. Replicate injections show a relative standard deviation not greater than 2.0%. 

In recent years, a small number of new phases have become available that are more suited to CEC. Phase Separations (Deeside. UK) have produced a SCX stationary phase. This is a strong cation-exchange material which contains aminopropyl-derivatised silica that has sulphonic acid groups covalently attached to the amino end of a short alkyl chain. The sulphonic acid groups are effectively ionised at all working pHs due to their low p/faS. Fig. 4.5 shows the dependence of EOF on pH of the mobile phase for a capillary packed with Phase Separations SCX stationary phase. The EOF is almost the same over the whole range. It increases beyond pH 7, presumably due to the added ionisation of the surface silanols. 

As described in Section 6.2.5, a family of ion exchangers can be obtained from polysuccinimide silica poly(2-sulfoethyl aspartamide) is an aliphatic strong cation exchanger, and polyaspartic acid is a weak cation exchanger. The primary use of this family of products is in the area of protein and peptide separations. These packings exhibit a superior column efiiciency compared to th coimterparts based on organic polymers. 

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