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Chiral mobile phase additives are widely used in high performance liquid chromatography (HPLC), which is used for separation of enantiomers. When chiral mobile phase additives are added to the mobile phase, diastereoisomerism complexes can be formed between the chiral mobile phase additives and the enantiomer solute through hydrogen bonds, ionic bonds, coordination bonds, or hole inclusion, so as to achieve the purpose of separation. Chiral mobile phase additives can be divided into several categories.
Cyclodextrin chiral mobile phase additives: Cyclodextrin (CD) is a cyclic oligosaccharide homologue. The cavity interior of cyclodextrin is hydrophobic due to the presence of -CH and -O-. The outer cavity of cyclodextrin is hydrophilic due to the presence of hydroxyl groups. The hydrophobic cavity part of the cyclodextrin molecule can be co-operated with the hydrophobicity part of the enantiomer molecule, while the hydroxyl group at the edge of the cavity can interact with the polar groups in the enantiomer molecule (such as -OH, -NH2) through hydrogen bond and other polar interactions. Therefore, chiral separation can be achieved. The size and type of the inclusion molecules vary with the inner diameter of the cyclodextrin cavity. It can only be separated if the guest molecule is just the right size to allow the nonpolar part to enter the cyclodextrin cavity. At present, β-cyclodextrin with medium size is widely used in the separation of enantiomers. It can be used for good separation of substances with naphthalene rings, double rings and poly-substituted benzene rings.
Vancomycin chiral mobile phase additives: Vancomycin is a glycopeptide antibiotic with basket structure, which contains eighteen asymmetric centers, nine hydroxyl groups, two amine groups and three condensed rings. Therefore, the separated compounds can be included in the basket structure. The rim of the basket structure contains a carboxyl group and a secondary amine group, which can be recognized by electrostatic interaction, hydrogen bonding, stereoscopic recognition, and π-π reaction. Therefore, vancomycin is a highly efficient chiral mobile phase additives.
Others: In addition to the above mentioned, there are other types of chiral mobile phase additives. For example, when chiral metal complexes are introduced into HPLC mobile phase, diastereotopic ternary complexes can be formed, and the separation of enantiomers can be achieved. In addition, the tartaric acid derivatives chiral mobile phase additives are commonly used in the separation of basic compounds.
Separation of methocarbamol enantiomers: Methocarbamol, commonly used as a supplementary treatment for muscle sprains, psoas strain, sciatica, and other diseases, has a chiral carbon atom in the molecular structure. Using carboxymethyl-β-cyclodextrin as a chiral mobile phase additives, the enantiomers of methocarbamol can be separated by HPLC.
Separation of dansyl amino acid enantiomers: Vancomycin chiral mobile phase additives can be applied to separate dansyl amino acid enantiomers. The carboxyl anion in the dansyl amino acid molecule and the protonated amine group in the vancomycin molecule will generate electrostatic interaction. In addition, there is also electrostatic interaction between the protonated tertiary amine group in dansyl amino acid molecular structure and the carboxyl anion in the ancomycin molecule. Using these two effects, the separation of dansyl amino acid enantiomers can be realized.
Others: Many other enantiomers can be separated by chiral mobile phase additives, including mandelic acid, lansoprazole, pantoprazole and the others.
Alfa Chemistry is one of the largest providers of chiral mobile phase additives in the world and the quality assurance is of prime importance to Alfa Chemistry. The solvent from Alfa Chemistry in the world is synonymous with reliability and excellent quality. Because of the exacting nature of our business and the regulatory demands placed upon our industry, Alfa Chemistry continues to be at the forefront in terms of compliance, accreditations and certifications.