Analysis of Zolmitriptan and Related Compounds Using the Agilent 7100 Capillary Electrophoresis System

Importance of the Topic

The accurate determination of zolmitriptan and its related impurities is essential for quality control in pharmaceutical development and manufacturing. Capillary electrophoresis (CE) provides high efficiency, fast separations, and minimal solvent consumption, making it an attractive complement or alternative to traditional liquid chromatography methods for routine API and impurity profiling.

Objectives and Study Overview

This study aimed to replicate and validate the United States Pharmacopeia (USP) method for zolmitriptan analysis using the Agilent 7100 CE system. The focus was on comparing separation performance, resolution, and repeatability against established USP criteria when analyzing zolmitriptan API and its related compounds.

Methodology and Instrumentation

Samples and Reagents:

• Zolmitriptan reference standard and related impurity standards (compounds F, G, and the R-isomer).
• Internal standard: tryptamine hydrochloride at 0.2 mg/mL.
• Sodium borate decahydrate buffer (19.1 g/L, adjusted to pH 2.1) and hydroxypropyl cyclodextrin (50 mg/mL).
• Diluent: 0.02 M hydrochloric acid.

Instrument and Software:

• Agilent 7100 Capillary Electrophoresis system.
• Agilent OpenLab CDS ChemStation (Rev. C.01.07 [27]).

Operational Parameters:

• Capillary: uncoated fused silica, 75 µm inner diameter, 56 cm total length.
• Voltage: optimized at 20 kV for best resolution of zolmitriptan and impurities.
• Temperature: 25 °C.
• Injection: 50 mbar for 5 s.
• Detection: UV at 200 nm.

Capillary Conditioning:

1. Flush inlet with 1 N NaOH (10 min), 0.1 N NaOH (5 min), and water (5 min).
2. Flush outlet with Milli-Q water.
3. Equilibrate with running buffer (inlet 4 min, outlet collected).

Main Results and Discussion

Voltage Optimization:
A range of 15–22 kV was tested. At 15 kV, one impurity (compound F) co-eluted with zolmitriptan; 20 kV provided baseline resolution for all peaks.

System Suitability:

• All critical resolution values exceeded the USP criterion of 1.5.
• Relative migration times matched USP values within acceptable deviation.
• %RSD for replicate injections was 2.4%, well below the 5% limit.

Electropherogram Analysis:
Distinct peaks for the internal standard, zolmitriptan, related compounds F and G, and the R-isomer were observed with clear separation and reproducible migration times.

Benefits and Practical Applications

• Green analytical technique: minimal solvent usage and waste generation.
• High efficiency and selectivity for challenging separations.
• Versatility: a single CE instrument can perform multiple separation modes.
• Compliance with pharmacopeial requirements for impurity profiling in quality control labs.

Future Trends and Opportunities

Integration of CE with mass spectrometry for enhanced sensitivity and structural confirmation.
Development of automated sample preparation workflows to increase throughput.
Expansion of CE methods for other small-molecule APIs and complex biologics.
Advances in microfluidic CE formats for point-of-care and portable analysis.

Conclusion

The Agilent 7100 CE system successfully replicated the USP method for zolmitriptan and its impurities, achieving required resolution and precision. This work demonstrates CE as a robust, green alternative to LC for routine pharmaceutical analysis.

References

• Agilent Technologies, Inc. Application Note 5994-0205EN, September 2018. Analysis of Zolmitriptan and Related Compounds Using the Agilent 7100 Capillary Electrophoresis System.