Analysis of Anionic Surfactants by Prominence-i and RF-20Axs Fluorescence Detector

Significance of the Topic

Monitoring anionic surfactants in water is essential for environmental protection and compliance with regulatory standards. Fluorescence detection combined with high-performance liquid chromatography (HPLC) offers sensitive, selective analysis of these compounds at trace levels.

Objectives and Study Overview

This application note evaluates the performance of the Shimadzu Prominence-i integrated HPLC system paired with the RF-20Axs high-sensitivity fluorescence detector. The focus is on quantitative analysis of five branched-chain anionic surfactants (C10–C14) in accordance with Japanese water quality inspection methods.

Methodology and Instrumentation

The separation of surfactant homologues was tested using two columns:

• Shim-pack VP-ODS (250 × 4.6 mm, 5 µm) at 1.0 mL/min
• Wakosil AS-Aqua (250 × 4.6 mm, 5 µm) at 0.7 mL/min

Mobile phase consisted of water (A) and acetonitrile with 0.1 M sodium perchlorate (B, 65 % B). Column temperature was maintained at 40 °C. Detection wavelengths were Ex 221 nm and Em 284 nm.

Key Results and Discussion

Chromatograms obtained with the VP-ODS column resolved branched isomers, while the AS-Aqua column delivered a faster analysis with one peak per carbon number. Repeatability tests (n=6) at 1 mg/L and 5 mg/L showed peak area %RSD ≤ 0.6 % on both columns. Direct injection of tap water spiked at 0.04 mg/L each yielded signal-to-noise ratios ≥ 6 for the weakest C14 isomer.

Benefits and Practical Applications

The integrated Prominence-i system with RF-20Axs provides:

• High sensitivity and low detection limits for anionic surfactants
• Robust repeatability suitable for routine QA/QC
• Direct injection capability of untreated water samples
• Efficient separation using selectable column chemistries

Future Trends and Opportunities

Advances may include online monitoring of surfactant levels, miniaturized HPLC modules for field use, greener mobile phase formulations, and integration with automated sample preparation for higher throughput.

Conclusion

The Prominence-i HPLC coupled with the RF-20Axs detector meets regulatory requirements for anionic surfactant analysis, delivering reliable, sensitive, and user-friendly operation for environmental laboratories.

Reference

Ordinance No. 101 and No. 261 of Japan’s Ministry of Health, Labour and Welfare (2003, revised 2011/2012). Shimadzu Application News L477, November 2014.