Implementation of a Walk-Up High- Pressure Capillary Ion Chromatograph for the Fast Separation of Pharmaceutical Relevant Inorganic Anions and Cations

Importance of the Topic

Ion chromatography is a cornerstone analytical technique for monitoring inorganic ions in the pharmaceutical industry. The introduction of high-pressure capillary formats enhances separation speed, reduces eluent consumption, and enables continuous “walk-up” operation, addressing the need for rapid, reliable QC and R&D workflows.

Objectives and Study Overview

This work documents the design and performance evaluation of a walk-up high-pressure capillary ion chromatograph (HPIC) for ultrafast separation of inorganic anions and cations common in pharmaceutical formulations. The study aims to demonstrate system stability, reproducibility, and throughput improvements under Always On, Always Ready conditions.

Methodology and Instrumentation

The capillary IC method uses suppressed conductivity detection and electrolytic suppressors for both anions and cations. Sample tablets (e.g., Metformin HCl, Fexofenadine HCl, Naproxen sodium, Atorvastatin calcium) were ground, dissolved in water at 45 °C, filtered through OnGuard RP and 0.5 µm IC filters, and diluted 1:10. Instrumentation comprised:

• Thermo Scientific™ Dionex™ ICS-5000 Reagent-Free™ Capillary IC system
• DP Dual isocratic capillary pump
• DC Detector and Chromatography Module
• IC Cube capillary module compartment
• CD Capillary Conductivity Detector for Anions and Cations
• EG Eluent Generator with capillary EGC cartridge (up to 200 mM eluent at 5000 psi)
• AS-AP Autosampler with diverter valve
• Chromeleon™ Chromatography Data System

Key Results and Discussion

The IC system operated continuously for over 80 days with negligible drift. Peak-to-peak baseline noise remained low, and anion retention time reproducibility stayed under 0.15% over 90 days. Linearity for cations and anions exceeded r2 = 0.999. Flow-rate increases from 10 to 18 µL/min for anions halved analysis time for 19-ion mixes; cation runs dropped from 18 min to under 6 min at 30 µL/min. Counterion determinations in commercial tablets achieved sensitive, selective quantification of fluoride, chloride, sodium, calcium, and other species, illustrating method robustness in real samples.

Benefits and Practical Applications

The Always On, Always Ready workflow eliminates manual eluent prep, shortens equilibration, and reduces downtime. Capillary IC consumes only ≈15 mL DI water per day, lowering operating costs. High-pressure capabilities enable high throughput, increased resolution with small-particle resins, and simple walk-up usage requiring minimal operator training.

Future Trends and Possibilities

Advances may include integration with mass spectrometry for ion speciation, automated sample handling for higher sample loads, development of new capillary stationary phases for challenging analytes, and networked remote monitoring to support decentralized QC environments.

Conclusion

High-pressure capillary IC with reagent-free operation redefines ion chromatography in pharmaceutical analysis by delivering ultrafast, reproducible separations in a user-friendly, always-on format. It offers significant time and cost savings, robust multiuser operation, and the potential for further enhancements in speed and resolution.

References

• Thermo Fisher Scientific. Dionex Application Note 106, Ion Chromatography in the Pharmaceutical Industry.
• Thermo Fisher Scientific. Dionex Application Note 164, Assay for Citrate and Phosphate in Pharmaceutical Formulations Using Ion Chromatography.