Daicel has introduced specific Chiral Stationary Phases to increase the potential for enantiomer separation in a number of special applications.
Zwitterionic Chiral Stationary Phases
Chiral Technologies expanded its extensive portfolio of immobilized stationary phases to include two novel zwitterionic chiral stationary phases, CHIRALPAK® ZWIX(+) and CHIRALPAK ZWIX(-). The CHIRALPAK ZWIX selectors were developed for separation of a great variety of zwitterionic molecules, bearing wide functional diversity, and specifically, for separation of underivatized amino acids.
The ZWIX selectors are zwitterionic molecules that incorporate both anion- and cation-exchange functional groups. These novel ZWIX selectors exhibit exceptional enantioseparation capabilities toward zwitterionic molecules such as amino acids and peptides.
To learn more, click here.
Anion Exchange Chiral Stationary Phases
CHIRALPAK QN-AX and CHIRALPAK QD-AX are weak anion-exchange (AX) chiral selectors. They were developed by Prof. W. Lindner’s group in Vienna and are designed specifically for enantioselective HPLC of chiral acids and possess exceptional enantiomer separation capabilities for acidic chiral compounds containing carboxylic, phosphonic, phosphinic, phosphoric or sulfonic groups. Weakly acidic compounds such as phenols can also be separated.
These two phases are based on two complementary stereoisomeric quinine (QN) and quinidine (QD) derivatives. The O-9 (tert-butylcarbamoyl) quinidine and O-9 (tert-butylcarbamoyl) quinine selectors are immobilized on a 5-µm silica support. Due to their pseudo enantiomeric character they usually reveal reversed elution order for opposite enantiomers.
They can be used in reversed-phase (RP) mode or in polar organic mode (non-aqueous, polar organic solvents containing organic acids and bases as buffer constituents). In addition, the separation of chiral basic and neutral compounds may also be possible, but usually under normal-phase (NP) conditions. In this mobile phase mode, CHIRALPAK QD-AX and CHIRALPAK QN-AX behave like a standard Pirkle-type Chiral Stationary Phase.
They are compatible with all common HPLC solvents (e.g. methanol, acetonitrile, tetrahydrofuran, 1,4-dioxane or chloroform) as well as in a wide pH range spanning from pH 2 to 8. Typical buffers used in hydro-organic mode are acetate, formate, citrate and phosphate.
Applications of QD-AX and QN-AX selectors for separation of chiral compounds can be found in our Technical Library.
Crown Ether Chiral Stationary Phases
CROWNPAK® CR(+) & CR(-) contain a chiral crown ether as a chiral selector, which is coated onto a 5-µm silica support. CROWNPAK selectors are mainly used to separate chiral amino acids and other small molecules with primary amine groups. The elution order of the enantiomers can be reversed when necessary.
Acidic mobile phases such as perchloric acid (pH 1 to 2), are used to operate these columns under standard conditions. To shorten the retention time of hydrophobic samples, the addition of methanol (15% maximum v/v) has been shown to be effective for CROWNPAK CR(+) & CR(-).
CROWNPAK CR-I(+) & CR-I(-) stationary phases and columns are the newest addition to this family of chiral selectors. The crown ether selectors are immobilized on 5-µm silica support. Immobilization extends the range of solvents used for mobile phases such as acetonitrile and ethanol, thereby enhancing enantioselective resolution of chiral compounds. Use of the immobilized CROWNPAK CR-I(+) & CR-I(-) selectors also provides longer column life time.
Ligand Exchange Chiral Stationary Phases
CHIRALPAK WH & MA(+) contain amino acids and their derivatives as chiral selectors. These columns are ligand-exchange type columns and employed with an aqueous solution of copper sulfate (0.1 to 2mM). The columns can tolerate use of organic modifiers such as methanol and acetonitrile to affect the separation.