**2.6. Boronate affinity chromatography**

In case of use boronic acid or boronates as ligand of the affinity chromatography, this type of methods are called boronate affinity chromatography. Most of the boronate derivatives are known to bind compounds with cis-diol groups covalently at a pH above 8. Separation of glycoproteins from non glucoprotein structures is possible by boronate affinity method due to cis-diol groups of the sugars. For instance, this method may successfully performed to seperate glucohemoglabin and normal hemoglobin or to determine different types of glyco‐ proteins in a sample [1].

There are many other chromatographic methods which are closely related to traditional affinity chromatography. For example **Analytical Affinity Chromatography** (**Quantitative Affinity Chromatography** or **Biointeraction Chromatography**) which is used as a tool for determination of solute-ligand interactions [21]. It is possible to investigate several biological systems, such as lectin/sugar, enzyme/inhibitor, protein/protein, DNA/protein interactions as well as binding of drugs or hormones to serum proteins with this technique. Thus competition of drugs with other drugs or endogenous compounds for protein binding sites may success‐ fully be detected by this method. Either immobilized drugs or immobilized proteins may be used in the studies about drug-protein and hormone-protein binding, although protein-based columns which may be use for multiple experiments are more common [1,29]. The competition between two solutes for binding sites can also be examined by this method and this technique is known as **Frontal Affinity Chromatography** [21]. **Hydrophobic Interaction Chromatogra‐ phy** and **Thiophilic Adsorption** methods also related to affinity chromatography. Immobi‐ lized thiol groups are used as ligands in **Thiophilic Adsorption** (**Covalent/Chemisorption Chromatography**) in order to separation of sulfhydryl-containing peptides or proteins and mercurated polynucleotides. In **Hydrophobic Interaction Chromatography** short non-polar chain, such as those that were originally used as spacer arms on affinity supports provide binding with proteins, peptides and nucleic acids. **Chiral Liquid Chromatography** methods can be also considered as affinity based techniques [21]. These techniques are widely utilized in pharmaceutical industry and clinical chemistry for the separation of individual chiral forms of the drugs and the quantification of different chiral forms of drugs or their metabolites. Since most of the ligands used in affinity chromatography are chiral, they may be preffered as stationary phases for chiral seperations. Protein-based and carbohydrate-based ligands may be used as the stationary phases in the analysis of chiral compounds via HPLC [1]. Orosomu‐ coid (α<sup>1</sup> -acid glycoprotein), bovine serum albumine and ovomucoid (a glucoprotein of egg whites) are some examples of protein-based stationary phases, while cyclodextrins (especially β-cyclodextrin) are of carbohydrate-based stationary phases [1,29].
