Limit of choline in succinyl- choline on a Metrosep C Supp 1 - 150/4.0 closely following USP

Significance of the Topic

Accurate determination of choline as an impurity in succinylcholine is critical for ensuring drug safety and meeting pharmacopeial requirements.
Succinylcholine is used for short-term muscle relaxation in clinical settings, and residual choline content must comply with USP limits to avoid adverse effects.

Objectives and Study Overview

The primary purpose of this application note is to adapt and validate an ion chromatography (IC) method for quantifying choline in succinylcholine solutions.
The study examines whether a Metrosep C Supp 1 - 150/4.0 column with modified eluent performs comparably to the official USP procedure.

Methodology

Sample Preparation:

• Succinylcholine solution at 50 mg/mL was diluted 1:20 with ultrapure water.

Chromatographic Conditions:

• Column: Metrosep C Supp 1 - 150/4.0 with Metrosep C Supp 1 Guard/4.0.
• Eluent: 4.0 mmol/L HNO3, 50 µg/L Rb+, 4.8% acetonitrile.
• Suppressor: Sequential suppression using 70 mmol/L sodium carbonate and sodium hydrogen carbonate with 30% acetonitrile regenerant.
• Flow rate: 1.0 mL/min; injection volume: 5 µL; column temperature: 40 °C; sample temperature: 4 °C.
• Runtime: 18 minutes; Pmax: 15 MPa.

Used Instrumentation

The analysis employed Metrohm Compact IC Flex series instruments:

• 930 Compact IC Flex Oven/SeS/Deg.
• IC Conductivity Detector.
• 889 IC Sample Center cooled autosampler.
• 800 Dosino for suppressor regeneration with MSM-HC Rotor C.

Main Results and Discussion

Only choline was detected among monitored cations; sodium, potassium and calcium were below the quantification limit.
Measured choline concentration was 465 mg/L, corresponding to 0.93% relative to the succinylcholine sample.
System suitability tests showed RSD of 0.5% (n=3) and 0.5% (n=8), with resolution between K+ and choline of 6.79, meeting USP criteria.
Despite using a slightly different eluent composition, the method produced precise and well-resolved choline peaks.
The measured impurity level exceeded USP limits, indicating non-compliance of the tested sample.

Benefits and Practical Applications

This modified IC approach provides a robust alternative to the USP method while using readily available columns and eluents.
High resolution and low RSD enable reliable routine screening of choline in paralyzing agents for quality control laboratories.

Future Trends and Applications

Further developments may include:

• Integration of mass spectrometric detection for enhanced selectivity.
• Automation of sample preparation to increase throughput.
• Extension of the method to other quaternary ammonium impurities in pharmaceutical formulations.

Conclusion

The application note demonstrates that Metrosep C Supp 1 columns with a tailored eluent achieve USP-compliant performance for choline determination.
This method allows pharmaceutical labs to verify choline impurity levels efficiently, although the tested sample failed to meet specification.

Reference

No external literature references were provided in the source document.