Polyacrylic Acid Using Acclaim SEC-1000 with Charged Aerosol versus UV Detection

Importance of the Topic

The analysis of polyacrylic acid (PAA) and cetylpyridinium salts in mouthwash formulations is essential for quality control and ensuring product safety. PAA serves as an antibacterial agent and scale suppressor, while cetylpyridinium provides antimicrobial benefits. Accurate quantification at low concentrations is required to meet regulatory standards and to monitor efficacy.

Objectives and Study Overview

This application note evaluates an ion exclusion chromatography method using the Acclaim SEC-1000 column with surfactant plus chemistry. The goal is to separate high-molecular-weight PAA from low-molecular-weight cationic species like cetylpyridinium with improved peak shape and sensitivity. Detection techniques compared include corona charged aerosol, suppressed conductivity, and UV at 220 nm.

Methodology and Instrumentation

• Chromatographic System: Thermo Scientific ICS-3000 IC system with UltiMate 3000 pump and Dionex modules
• Columns: Acclaim SEC-1000 (7 µm, 7.8 × 150 mm) and Acclaim Surfactant Plus (3 µm, 3.0 × 150 mm)
• Mobile Phase (Gradient): Solvent A – 10% acetonitrile/90% water; Solvent B – 100 mM acetonitrile/formic acid; Solvent C – water; flow rate 1.0 mL/min
• Gradient Profile: 0–12 min: 20% B, 80% C; 12–40 min: 40% B, 60% C
• Sample Injection: 5 µL; concentration range: 0.016–0.400 µg/mL for PAA and cetylpyridinium
• Detectors: Corona charged aerosol (2 Hz, 0.5 mL/min nebulizer); suppressed conductivity with CSRS 300 suppressor; UV diode array at 200–220 nm

Main Results and Discussion

• Unbuffered mobile phase eliminated strong electrostatic interactions, improving resolution between PAA and small cations compared to buffered systems
• PAA displayed a weak UV chromophore; charged aerosol detection yielded LOQ around 0.015 µg/mL, outperforming UV (LOQ >0.05 µg/mL)
• Cetylpyridinium quantified below 50 ppb with sharp, symmetrical peaks using the surfactant plus column
• Conductivity detection provided complementary quantification of ionic species but with higher noise than CAD for PAA

Benefits and Practical Applications

• High sensitivity and low detection limits ensure reliable monitoring of PAA and cetylpyridinium in consumer products
• Separation of polymers from small ions in a single run reduces analysis time and sample preparation complexity
• Unbuffered mobile phases simplify method development and minimize buffer-related maintenance

Future Trends and Potential Applications

• Coupling with mass spectrometry for structural confirmation and enhanced selectivity of PAA oligomers
• Miniaturized systems and on-line sample preconcentration to further lower detection limits
• Extension of this approach to other polymeric additives and surfactants in pharmaceutical and environmental analysis

Conclusion

The described ion exclusion chromatography method using Acclaim SEC-1000 with surfactant plus and charged aerosol detection offers a robust, interference-free approach for simultaneous quantification of polyacrylic acid and cetylpyridinium in mouthwash. The unbuffered gradient enhances separation, while corona CAD ensures superior sensitivity for weak chromophores.

Reference

1. Thermo Fisher Scientific Inc. Application Notes PB20627_E (2012) and PB20745_E (2013)