Enantiomeric purity determination of tamsulosin by capillary electrophoresis using cyclodextrins and a polyacrylamide-coated capillary

Abstract

The chiral separation of racemic tamsulosin hydrochloride (TH) was carried out using cyclodextrin (CD)-mediated capillary electrophoresis (CE) with DAD at 200 nm. The best separation of enantiomers of the studied compound was achieved at 20 kV with 30 cm × 50 μm I.D. polyacrylamide (PAA)-coated fused-silica capillary (effective length 20 cm) and running buffer with sulfated-β-CD (S-β-CD) as chiral selector. Other selected native or derivatized CDs were also tested: β-CD (5, 15 mmol l⁻¹), carboxymethyl-β-CD (5, 30 mmol l⁻¹), dimethyl-β-CD (15 mmol l⁻¹) and hydroxypropyl-β-CD (5, 30 mmol l⁻¹). Several parameters such as capillary pretreatment, buffer type and concentration, pH of background electrolyte, methanol content, separation temperature and voltage, were optimized. The excellent baseline separation of chiral TH was successfully achieved within 12 min using 100 mmol l⁻¹ phosphate buffer with pH 2.5 containing 1.7 mmol l⁻¹ S-β-CD. Rectilinear calibration range was 50.0–500.0 μmol l⁻¹ of each enantiomer (r = 0.9993–0.9996).

The method was applied to the assay of R-TH in Omnic, capsules (nominal content 0.4 mg per capsule) with R.S.D. 2.75% (n = 6), recovery 99.3–101.7% and it was suitable for the chiral purity control of the active enantiomer in the pharmaceutical.