Bromide and Organic Acids in Cough Syrup Using a Thermo Scientific™ Acclaim™ Organic Acid (OA) Column

Importance of Topic

Pharmaceutical formulations frequently include anionic species either as active-counterion pairs or inactive excipients. Accurate quantification of these anions is critical for quality control, regulatory compliance and ensuring dosage consistency. Traditional reversed-phase separations often struggle with small inorganic and organic anions, creating demand for specialized columns capable of reliable, high-resolution analysis.

Objectives and Study Overview

This application note demonstrates a method for simultaneous determination of bromide (originating from dextromethorphan hydrobromide) and two organic acids (citrate and succinate) in a commercial cough syrup (NyQuil®). The goal is to showcase the performance of the Thermo Scientific™ Acclaim™ Organic Acid (OA) column in separating and quantifying these anions under pharmaceutical quality control conditions.

Methodology

The separation was achieved using a 4 × 250 mm, 5 µm Acclaim OA column with an aqueous mobile phase (0.1 M Na₂SO₄, pH 2.68 adjusted with methanesulfonic acid). The column temperature was maintained at 30 °C and the flow rate set to 0.6 mL/min. UV detection at 210 nm provided adequate sensitivity for targeted anions. Sample preparation involved passing NyQuil syrup through an OnGuard II P cartridge to remove potential interferences prior to injection (5 µL volume).

Used Instrumentation

• HPLC system equipped with UV detector at 210 nm
• Thermo Scientific™ Acclaim™ OA column, 4 × 250 mm, 5 µm
• OnGuard II P cartridge for sample cleanup

Main Results and Discussion

The chromatogram exhibited three well-resolved peaks within a 15-minute runtime: bromide (from dextromethorphan HBr), citrate (inactive ingredient) and succinate (from doxylamine succinate). Baseline separation was achieved with retention times approximately at 3–5 min (bromide), 8–10 min (citrate) and 12–14 min (succinate). Peak shapes were symmetrical and system suitability criteria (resolution, repeatability) met typical pharmaceutical QC standards.

Benefits and Practical Applications

• Rapid, isocratic separation simplifies method development and reduces solvent consumption.
• High selectivity for small inorganic and organic anions ensures robust quantification in complex matrices.
• Standard sample cleanup with OnGuard II P cartridges minimizes matrix effects from viscous syrup formulations.

Future Trends and Potential Applications

Advancements in column chemistries and detection technologies may allow even faster run times and lower detection limits for trace anionic impurities. Coupling with mass spectrometry could expand the range of detectable anions, while automated sample preparation platforms promise higher throughput in pharmaceutical QC laboratories.

Conclusion

The Thermo Scientific Acclaim OA column provides a reliable, high-resolution solution for simultaneous analysis of bromide and organic acids in cough syrup formulations. Its compatibility with common sample cleanup techniques and standard HPLC systems makes it an accessible tool for routine pharmaceutical quality control.

Reference

Thermo Fisher Scientific Application Note 20025, 2009