RESOLUTION OF RACEMIC DRUGS ON A NEW CHIRAL COLUMN BASED ON SILICA-IMMOBILIZED CELLOBIOHYDROLASE - CHARACTERIZATION OF THE BASIC PROPERTIES OF THE COLUMN

The basic properties of a new chiral column based on silica-immobilized cellobiohydrolase 1 (CBH 1) were studied using 32 different drugs and endogenous compounds as model compounds. All the compounds were resolved with high separation factors and high resolution. The stability of the CBH 1 column was studied by pumping two different mobile phases through the column, one of pH 6 and the other of pH 7. A 34-1 volume of mobile phase, corresponding to about 38 000 column volumes, was pumped through the column. The enantioselectivity, the resolution, the separation efficiency and the retention of the test compounds were unchanged after the passage of 38 000 column volumes of mobile phase. The most important tool for affecting the enantioselectivity, resolution and retention is the pH of the mobile phase. Uncharged modifiers such as acetonitrile and 1- and 2-propanol were also used. Unique effects were obtained for a series of drugs and endogenous compounds, related to epinephrine, by increasing the 2-propanol concentration in the mobile phase from 0 to 20%. The capacity factor for the most retained enantiomer could be selectively increased by increasing the 2-propanol concentration in the mobile phase, resulting in a substantial improvement in the enantioselectivity. For one compound, octopamine, the capacity factor of the most retained enantiomer increased by almost 100%, resulting in a very large increase in the separation factor from 1.9 to 3.3. The resolution increased from 4.8 to 7.8. The relationship between the molecular structure and the enantioselectivity was also studied. The data indicate that the steric bulk on a basic nitrogen influences the enantioselectivity to a large extent, in addition to the degree of ring substitution. Further, the Chiral-CBH column seems to be very well suited for the resolution of preferentially basic drugs of different character.