Affinity chromatography aqueous phase

The aqueous or organic extract obtained at this step of analysis may be a very dilute solution of the analyte(s) of interest. It may also contain coextractives, which, if allowed in the final extract, will increase the background noise of the detector, making it impossible to determine trace level concentrations of the analyte(s). To reduce interferences and concentrate the analyte(s), the primary sample extracts are subjected to some kind of cleanup including liquid-liquid partitioning, solid-phase extraction, matrix solid-phase dispersion, online trace enrichment, affinity chromatography, immunoaffinity chromatography, and ultrafiltration. In many instances, more than one of these procedures may be used in combination to increase extract purification. 

Desalting can be achieved by precipitation with ethanolic atmnonium acetate [4], solid-phase extraction (SPE), microdialysis [13], Fe " -loaded immobilized metal affinity chromatography (IMAC) [14], cation-exchange coluttms (SCX) [15-16], or combinations thereof [17-18]. The SCX procedure can be applied on-hne with direct infusion of the effluent into ESl-MS [15-16]. The mobile phase applied is similar to the one applied in LC-MS, i.e., 50% acetonitrile in 10 mmol/1 aqueous TEA. 

The compatibility of all these PEG-based resins with aqueous buffers allows their use for biochemical applications such as on-resin screening of chemical libraries and in the development of affinity chromatography [58-61]. All these families of PEG-based resins, except POEPS, are free of aromatic rings. This feature makes these solid supports highly suitable for a broad range of applications where such rings can react with reagents or/and jeopardize the solid-phase NMR control of the reactions [62]. 

The principles of affinity chromatography can be combined with other operations of purification to improve them (Labrou and Clonis 1994). Affinity partition combines the selectivity of affinity ligation with aqueous two-phase extraction (Kamihira et al. 1992 Kohler et al. 1991) and has been successfully employed in enzyme recovery and purification (Johansson and Tjerneld 1989 Schustolla et al. 1992) obtaining impressive increases in the partition coefficient (Eq. 2.16) and therefore in yield of enzyme recovery (Eq. 2.17). Affinity partition has also been combined with membrane separation (affinity ultrafiltration), where a soluble... 

---