To establish a supercritical fluid chromatography (SFC) method for the determination of chiral purity of palonosetron hydrochloride using two columns in series, and to determine the isomers in palonosetron hydrochloride bulk drug and injections.

Two columns, DAICEL CHIRALPAK AD-3 (150 mm×3.0 mm, SFC, 3 μm) and DAICEL CHIRALPAK IG-3 (150 mm×3.0 mm, SFC, 3 μm), were in series. The column temperature was at 37 ℃, the mobile phase was composed of CO₂ and a mixture of anhydrous ethanol, acetonitrile, and diethylamine at a ratio of 55∶45, the back pressure was at 12 MPa, the flow rate was 1.2 mL·min^-1, the injection volume was 20 μL, and the detection wavelength was at 240 nm.

The R,S isomer, R,R enantiomer, S,R isomer, and palonosetron were eluted sequentially within 10 min with resolutions of 1.7, 2.3, and 1.5, respectively. All four compounds exhibited good linearity between peak area and concentration in the range from 0.20 to 10.0 μg·mL^-1, with r all greater than 0.999 5. The detection limits (S/N=3) of the three isomers were all 0.10 μg·mL^-1; and the quantitation limits (S/N=10) were all 0.20 μg·mL^-1. The average recoveries of the three isomers in the bulk drug and injections ranged from 97.8% to 101.3%, with relative standard deviations (RSDs) ranged from 0.3% to 1.5% (n=9). Except for one batch of bulk drug in which no chiral impurity was detected, the R,S isomer was detected in all the other five batches, with contents ranging from 0.03% to 0.12%.

The developed SFC method can separate palonosetron and its three isomers in a short analysis time, and the use of two columns in series improves the separation efficiency, especially the resolution between the S,R isomer and palonosetron. The method is accurate, reliable, and can be used as an effective means for chiral purity determination and quality control of palonosetron hydrochloride bulk drug and related preparations.