Limit of β-cyclodextrin (betadex) in betadex sulfobutyl ether sodium

Significance of the topic

Cyclodextrins are cyclic oligosaccharides widely used in pharmaceutical formulations as complexing agents to enhance solubility, stability, and bioavailability of poorly soluble drugs. Controlling residual β-cyclodextrin impurity in Betadex sulfobutyl ether sodium is essential to meet USP standards and ensure product safety and efficacy.

Objectives and scope

This study evaluated the USP monograph limit test for β-cyclodextrin in Betadex sulfobutyl ether sodium. It compared the official 3-potential pulsed amperometric detection method with two alternative 4-potential waveforms and assessed performance using a disposable gold working electrode for carbohydrate detection by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD).

Methodology and Instrumentation

• Instrumentation
  • Thermo Scientific Dionex ICS-5000+ HPIC system with DP dual pump, DC detector chamber and electrochemical detector
  • Dionex IonPac AS11 analytical column (4×250 mm) with AG11 guard column (4×50 mm)
  • Pulsed amperometric detection (PAD) using gold conventional and disposable working electrodes and an Ag/AgCl reference electrode
  • Dionex AS-AP autosampler and sample filtration units
• Eluent composition
  • Eluent A: 25 mM sodium hydroxide
  • Eluent B: 250 mM sodium hydroxide with 1 M potassium nitrate
• Sample preparation
  • Stock and calibration standards prepared at 2 000 mg/L and diluted to 0.4–3.5 mg/L
  • Sample solutions at 2 000 mg/L; spiked recoveries at 0.5 and 1.0 ppm
• Chromatographic conditions
  • Isocratic elution with 25 mM NaOH for 4 min, followed by 250 mM NaOH/1 M KNO₃ for column cleanup
  • Flow rate 1 mL/min, column temperature 50 °C, injection volume 20 µL, run time 20 min
  • Pulsed amperometric waveforms: USP 3-potential and two 4-potential cycles (0.5 s and 0.33 s)

Main results and discussion

• System suitability: RSD for retention time <0.2 %, area <0.8 % for all waveforms, meeting USP ≤5 % criteria.
• Sensitivity: LOD/LOQ of 0.015/0.052 mg/L with 3-potential waveform; 4-potential waveforms yielded LOD 0.042–0.066 mg/L.
• Linearity: calibration curves from 0.4 to 3.5 mg/L showed r² >0.999.
• Sample analysis: two commercial batches contained <0.1 % β-cyclodextrin (one undetectable, one at 0.066 %).
• Accuracy: spike recoveries ranged from 92 % to 108 %.
• Waveform comparison: 3-potential provided higher initial signal; 4-potential gave stable long-term response and more data points for early eluting cyclodextrin peaks.
• Disposable electrode performance: comparable signal-to-noise ratio, stable response over four weeks, reduced maintenance requirements.

Benefits and practical applications

• Fully compliant with USP Betadex sulfobutyl ether sodium monograph for β-cyclodextrin limit testing.
• High sensitivity detection of trace β-cyclodextrin impurity.
• Method flexibility supports choice of waveform and electrode type to suit laboratory throughput and maintenance needs.
• Disposable electrode option streamlines routine operation and reduces downtime.

Future trends and applications

Ongoing adoption of 4-potential waveforms and disposable electrode technology will enhance method robustness, reproducibility, and throughput. The approach may be extended to quantification of other cyclodextrin derivatives, excipient profiling, and in-process quality control throughout pharmaceutical manufacturing.

Conclusion

The validated HPAE-PAD method meets or exceeds USP requirements for β-cyclodextrin limit testing in Betadex sulfobutyl ether sodium. It offers reliable sensitivity, excellent precision, and operational flexibility. Negative potential waveforms and disposable gold electrodes further improve long-term reproducibility and ease of maintenance.

References

1. Vyas A, Saraf S, Saraf S. Cyclodextrin based novel drug delivery systems. J Incl Phenom Macrocycl Chem. 2008;62:23–42.
2. Challa T, Ahuja A, Ali J, Khar RK. Cyclodextrins in drug delivery: an updated review. AAPS PharmSciTech. 2005;6:E329–E357.
3. Brewster ME, Loftsson T. Cyclodextrins as pharmaceutical solubilizers. Adv Drug Deliv Rev. 2007;59:645–666.
4. United States Pharmacopeia 41–NF 36. Betadex Sulfobutyl Ether Sodium. USP. Rockville, MD; 2018:5224.
5. Kinalekar MS, Kulkarni SR, Vavia PR. Simultaneous determination of alpha, beta, and gamma cyclodextrins by LC. J Pharm Biomed Anal. 2000;22:661–666.
6. White G, Katona T, Zodda JP, Eakins MN. Determination of the impurity profile of γ-cyclodextrin by HPLC. J Chromatogr. 1992;625:157–163.
7. Agüeros M, Campanero MA, Irache JM. Simultaneous quantification of different cyclodextrins and Gantrez by HPLC-ELSD. J Pharm Biomed Anal. 2005;39:495–502.
8. Hammes W, Bourscheidt C, Büchsler U, Stodt G, Bökens H. Quantitative determination of α-cyclodextrin in human plasma by LC-ESI-MS. J Mass Spectrom. 2000;35:378–383.
9. Blum W, Aichholz R, Ramstein P, Fetz A, Raschdorf F. Determination of 2-hydroxypropyl-γ-cyclodextrin in plasma by GC-MS. J Chromatogr B. 1998;720:171–177.
10. Fukuda M, Kubota Y, Ikuta A, Hasegawa K, Koizumi K. Microanalyses of β-Cyclodextrin and Glucosyl-β-cyclodextrin in biological matrices by HPLC-PAD. Anal Biochem. 1993;212:289–297.
11. Haginaka J, Nishimura Y, Wakai J, Yasuda H, Koizumi K, Nomura T. Determination of cyclodextrins by RP-HPLC with PAD and a membrane reactor. Anal Biochem. 1989;179:336–344.
12. Koizumi K, Kubota Y, Tanimoto T, Okada Y. Determination of cyclic glucans by anion-exchange chromatography with PAD. J Chromatogr. 1988;454:303–310.
13. Thermo Scientific. Technical Note 71: Eluent Preparation for HPAE-PAD. 2013.
14. Thermo Scientific. Dionex ICS-5000 Ion Chromatography System Installation Instructions. Doc. 065343 Rev. 05. Dec 2011.
15. Thermo Scientific. Electrochemical Detection User’s Compendium P/N 065340-02. Apr 2013.
16. United States Pharmacopeia. Pharmacopeial Forum 36(2) In-Process Revision: Betadex Sulfobutyl Ether Sodium.
17. Thermo Scientific. Technical Note 21: Optimal Settings for PAD of Carbohydrates Using Dionex ED40. 2013.