EFFECT OF SULFOBUTYL ETHER BETA-CYCLODEXTRIN MODIFIER ON SELECTIVITY OF REVERSED PHASE HPLC SEPARATIONS

Abstract

Selectivity changes imparted by sulfobutyl ether beta-cyclodextrin (SBECD) modifier were evaluated in reversed phase HPLC separations. The mixed mode capabilities of SBECD, including cation exchange and an orthogonal hydrophobic interaction (i.e., via inclusion complex), altered the typical retention properties of a C18 column. This enabled several racemates (fenoterol, idazoxan hydrolyzate, orciprenaline, terbutaline, tranylcypromine, and imazalil) to be resolved. The selectivity of SBECD is distinct, as the related sulfated beta-cyclodextrin (SCD) modifier separated different racemates (1-aminoindane, fenoterol, both idazoxan and its hydrolyzate, nefopam, terbutaline, and tranylcypromine). The SBECD modifier also improved main peak resolution or altered impurity profiles for the fermentation-derived drug substances A40926, ramoplanin, teicoplanin, and vancomycin. Selectivity changes from SBECD were shown to be beneficial for chiral and chemical purity separations. Moreover, cyclodextrin modifier may enable a combined chiral and overall chemical purity method to be developed, which is not feasible by only using current chiral or reversed phase C18 columns alone. This study demonstrated that cyclodextrins and their derivatives are underutilized for HPLC and warrant consideration as a viable alternative to commercially available chiral or mixed mode columns.

Keywords:

• beta-agonist
• chiral
• cyclodextrin
• high performance liquid chromatography
• mixed mode
• pharmaceutical

ACKNOWLEDGMENT

The authors thank Dr. Vincent Antle of Cydex Pharmaceuticals, Inc. for gifts of SBECD with lesser average substitution; Dr. Ying Liu, Dr. Kelly Zhang and Dr. Michael Dong for useful suggestions; and Christopher Goretski for general assistance.

Notes

Note: Analytes eluted within a linear portion of the HPLC gradient [95:5 A:B at 0.0 min to 5:95 A:B at 30.0 min, where mobile phase A = H₂O:formic acid (100:0.05 v/v) containing SBECD (2.3 g/L) and mobile phase B = acetonitrile:formic acid (100:0.05 v/v)].

^a Analyte observed as split pea.k.

^b Analyte non-retained.

^c Results from extraction at 240 nm to account for interference in trial using SBECD modifier (all other results obtained at 205 nm).

^a Mobile phase B is 100% acetonitrile for all separations, except standard conditions (0.05% formic acid in acetonitrile).

^b Standard analysis conditions: 2.3 g/L SBECD (Average Substitution = 7.0) in 0.05% formic acid (mobile phase A).

^a Determined as peak area of main component divided by total peak area (main component and impurities).