Cation-exchange resin columns applications

Amino acids can be separated without prior derivatization on a cation-exchange resin column. The elution buffers are classically lithium citrate buffers with different pH values and salt concentrations, which are applied stepwise. There is usually a programmed increase in column temperature. Consequently, there are numerous variables affecting the separation of the individual amino acids [6]. For the detection of the amino acids, the column effluent is mixed with the ninhydrin reagent. Nowadays there are only very few manufacturers of AAAs left. The considerable cost of purchase and the operation costs are a potential threat to the widespread application of this technique, although it is still considered to be the definitive method for diagnosing disorders of amino acid metabolism. 

Yamamoto et al. (1982) developed a quantitative method for the determination of putrescine, cadaverine, spermidine, and spermine in foods. Separation of the amines from foods was achieved by eluting through a cation-exchange resin column and then converted to their (ethyloxy) carbonyl derivatives by the reaction with ethyl chloroformate in aqueous medium before application to the gas chromatograph with a flame ionization detector. They used 1,8-diaminooctane as an internal standard and performed the separation and determination of the resulting derivatives on a 1.5% SE-30/0.3% SP-1000 on Uniport HP column (0.5 m) under the temperature-programmed condition. Staruszkiewicz and Bond (1981) developed a GLC procedure for the quantitative determination of the diamines putrescine... 

Ing retention of "free" water in the resin. While the Ca -form resin retained even less "free" water, polyols and ribose were strongly retained due to complex formation. It was confirmed that the best separation of hexoses and pentoses is obtained with the Ca -form resin, while for sugar alcohols and polyols, the -form was best. Specific applications of cation-exchange resin columns include the determination of low levels of monosaccharides, alditols, and cyclltols in sheep plasma on a Ca -form column with u.v. detection at 190 nm, an extension of this involving collection... 

Another, relatively simple method, also applicable to plasma samples, is as follows. Bio-Rad AG 50W-x8, 100-200 mesh cation exchange resin (7,5 g) was packed into a 10-mL disposable glass pipette (0.85 x 16.5 cm) and conditioned with 0.5 M HCI (Tam et al., 1979). One millilitre of plasma, urine or arsenic reference solution was applied to the top of the column. Then, the column was eluted successively with 0.5 M HCI (As(lll) and As (V), deionized water (MMA). and first 5% (v/v). then 20% (v/v) ammonia (DMA). A modification of the elution procedure, using 0.5 M HCI, deionized water and 1.5 M perchloric acid, has been reported by Marafante et al. (1987). Arsenic may be detected by gamma counting for radioiabeiled arsenic or XRF or hydride AAS for nonradioactive arsenic compounds (Tam et al. 1979 Vahter, 1986). Separation of As(lll) and As(V) in the HCI fractions has been performed using a weakly basic resin (AG3-X4A, 100-200 mesh. Bio Rad) (Vahter and Envall, 1983). The HCI-fractions were neutralized with NaOH and applied to the column. As (III) was eluted with 0.01 M phosphate buffer, pH 6.9, and As(V) with 1 M HCI. 

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