Enantioseparation of Citalopram by RP-HPLC, Using Sulfobutyl Ether-β-Cyclodextrin as a Chiral Mobile Phase Additive

Abstract

Enantiomeric separation of citalopram (CIT) was developed using a reversed phase HPLC (RP-HPLC) with sulfobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive. The effects of the pH value of aqueous buffer, concentration of chiral additive, composition of mobile phase, and column temperature on the enantioseparation of CIT were investigated on the Hedera ODS-2 C18 column (250 mm × 4.6 mm × 5.0 um). A satisfactory resolution was achieved at 25°C using a mobile phase consisting of a mixture of aqueous buffer (pH of 2.5, 5 mM sodium dihydrogen phosphate, and 12 mM SBE-β-CD), methanol, and acetonitrile with a volumetric ratio of 21 : 3 : 1 and flow rate of 1.0 mL/min. This analytical method was evaluated by examining the precision (lower than 3.0%), linearity (regression coefficients close to 1), limit of detection (0.070 µg/mL for (R)-CIT and 0.076 µg/mL for (S)-CIT), and limit of quantitation (0.235 µg/mL for (R)-CIT and 0.254 µg/mL for (S)-CIT).

Figure 1

Structure of (R, S)-citalopram.

Figure 2

Structure of SBE-β-CD.

Figure 3

Effect of the pH of aqueous buffer. Mobile phase: aqueous buffer/methanol/acetonitrile of 21 : 3 : 1 (v/v/v); 5 mM sodium dihydrogen phosphate, 12 mM SBE-β-CD, flow rate of 1.0 mL/min, detection wavelength of 240 nm, and temperature of 25°C. K _R and K _S, retention factors of (R)-CIT and (S)-CIT, respectively; R, resolution.

Figure 4

Effect of the concentration of sodium dihydrogen phosphate. Mobile phase: aqueous buffer/methanol/acetonitrile of 21 : 3 : 1 (v/v/v), C_NaH2PO4, concentration of sodium dihydrogen phosphate in aqueous buffer of 0, 5, 8, and 12 mM, 12 mM SBE-β-CD, pH of 2.5, flow rate of 1.0 mL/min, detection wavelength of 240 nm, temperature of 25°C, K _R and K _S, and retention factors of (R)-CIT and (S)-CIT, respectively; R, resolution.

Figure 5

Typical chromatogram of CIT enantiomers. Mobile phase: aqueous buffer/methanol/acetonitrile of 21 : 3 : 1 (v/v/v), 5 mM sodium dihydrogen phosphate, 12 mM SBE-β-CD, pH of 2.5, flow rate of 1.0 mL/min, detection wavelength of 240 nm, temperature of 25°C, and injection of 10 μL and 0.22 mM of racemic CIT.