Exchange Liquid Chromatography

EC = ion exchange chromatography IPC = ion pair chromatography LSC = liquid—solid chromatography... 

Swallow, K. W. and Low, N. H. (1994). Determination of honey authenticity by anion-exchange liquid chromatography. /. Assoc. Offic. Anal. Chem. 77, 695-702. 

Figure 4.27 Flow chart for coluwi selection based on sample type (m - molecular weight). PLC precipitation-liquid chromatography SEC = size-exclusion chromatography lEC - ion-exchange chromatography HIC hydrophobic interaction chromatography LSC liquid-solid chromatography RPC - reversed-phase liquid chromatography BPC (polar) bonded-phase chromatography and IPC - ion-pair chromatography.

Law, B. and Weir, S., Quantitative structure-retention relationships for secondary interactions in cation-exchange liquid chromatography, ]. Chromatogr. A, 657, 17, 1993. 

Alonso, ]., Nogues, M. V., and Cuchillo, C. M. Separation of RNA derivatives by high-performance anion-exchange liquid chromatography, J. Liq. Chromatogr., 8, 299, 1985. 

Anacardio, R., Cantalini, M.G., De Angelis, F., and Gentile, M., Quantification of S-carboxymethyl-(R)-cysteine in human plasma by high-performance ion-exchange liquid chromatography/atmospheric pressure ionization mass spectrometry, /. Mass Spectrom., 32, 388, 1997. 

Hanai, T., Miyazaki, R., and Kinoshita, T., Quantitative analysis of human serum albumin-drug interactions using reversed phase and ion-exchange liquid chromatography, Anal. Chim. Acta, 378, 77, 1999. 

Simpson, R. C. Fenselau, C. Hardy, M. R. Townsend, R. R. Lee, Y. C. Cotter, R. J. Adaptation of a thermospray liquid chromatography/mass spectrometry interface for use with alkaline exchange liquid chromatography of carbohydrates. Anal. Chem. 1990, 62, 248-252. 

The separation of mono-, di-, and tributyltin species in seawater by isocratic ion exchange liquid chromatography coupled to hydride generation AAS has been reported by Schulze and Lehmann [107]. Reported detection limits are 31,40, and 27 mol/1, respectively. 

Spherical porous silica gel is the easiest stationary phase material to handle however, although it is physically strong it is chemically unstable. Surface modification can expand its capability for different modes of chromatography, such as normal-phase, reversed-phase, size-exclusion, and ion-exchange liquid chromatography. These stable modifications are performed by chemical deriva-tization of the surface silanol groups. 

Figure 4.8 Cation-exchange liquid chromatography of basic proteins. Column, Asahipak ES502C eluent, 20 min linear gradient of sodium chloride from 0 to 500 mM in 50 mM sodium phosphate buffer pH 7.0 flow rate, 1 ml min-1 temperature, 30 °C detection, UV 280 nm. Peaks 1, myoglobin from horse skeletal muscle (Mr 17 500, pi 6.8-7.3) 2, ribonuclease from bovine pancreas (Mr 13 700, pi 9.5-9.6) 3, a-chymotrypsinogen A from bovine pancreas (Mr 257 000, pi 9.5) and 4, lysozyme from egg white (Mr 14 300, pi 11.0-11.4). (Reproduced by permission from Asahikasei data)...

The selection of the counter-ion and its concentration are important for the separation of ionic compounds in reversed-phase and ion-exchange liquid chromatography. The addition of hydrophobic ions is an especially powerful method and several surfactants can be used as hydrophobic counter-ions. The theoretical column efficiency of ion-pair liquid chromatography is much better than that of an ion-exchange column, and the regeneration of a column is much faster. Thus, if we can control ion-pair liquid chromatography, we can solve a separation problem. (The important background sources in this area are listed at the end of the chapter.)... 

Ion-pair liquid chromatography can be applied to compounds separated by ion-exchange liquid chromatography, and mixtures of ionic and non-ionic compounds are easily separated. The latter separation is difficult by ion-exchange liquid chromatography. Anions can be separated by reversed-phase ion-pair liquid chromatography (Figure 4.18). 

SEC is a useful tool for monitoring enzyme reactions, as seen in Figure 4.21, where the speed of decomposition of /Mactoglobulin by a-chymotrypsin is shown. SEC is widely used for purification of proteins, but the separation is due only to the difference in molecular mass. Therefore, ion-exchange liquid chromatography is combined with SEC to improve the selectivity. 

To increase Vs, the chromatographer can increase the surface area of the stationary phase materials in normal-phase liquid chromatography, increase the stationary phase volume in reversed-phase or partition liquid chromatography, or increase the ion-exchange capacity in ion-exchange liquid chromatography. In general, if the internal diameter of a column is constant, the retention time... 

Boyle et al. [47] have described a method for determining cobalt in non saline waters using cation exchange liquid chromatography. Cobalt was determined directly in 500pL fresh water samples with a detection limit of 20pM per kg. 

Other methods to detect adulteration include anion-exchange liquid chromatography in combination with pulsed amperometric detection (Stuckel and Low, 1995) and FTIR, FT-Ramen, and NIR Spectroscopy (Paradkar et al., 2002, 2003). 

Stuckel, J. G. and Low, N. H. (1995). Maple syrup authenticity analysis by anion-exchange liquid chromatography with pulsed amperometric detection. J. Agric. Food Chem. 43, 3046-3051. 

Figure 10 Cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS) of arsenic species spiked in (a) aqueous solution and (b) urine diluted (1 + 3). Amount of each species injected 0.44 ng. Peaks (1) DMA (2) As (III) (3) MM A (4) As (V) (5) AsB (6) TMAO (7) AsC (8) TMAs. (From Ref. 69.)...

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