Analysis of Isopropyl methylphenol(IPMP)

Significance of the Topic

Isopropyl methylphenol (IPMP) is a common antibacterial agent employed in medical and personal care soaps to inhibit microbial growth. Regulatory bodies such as the European Chemicals Agency (ECHA) and the U.S. Food and Drug Administration (FDA) increasingly require sensitive, reliable assays for active ingredients in consumer products. A fast, robust chromatographic method supports quality control in manufacturing, compliance with safety standards and protection of end users.

Objectives and Study Overview

This application note presents the development and comparison of two reversed-phase HPLC protocols for the determination of IPMP at 5 mg/L in soap formulations. The study contrasts a conventional 5 µm column with a high-speed 2 µm format to evaluate throughput, resolution and method performance under regulatory-style conditions.

Methodology and Equipment

Two analytical schemes were optimized using Shimadzu’s reversed-phase Shim-pack GIST C18 column:

• Conventional Mode: 250 × 4.6 mm, 5 µm particle, 1.0 mL/min flow, 50:50 water:acetonitrile, 40 °C, 10 µL injection.
• High-Speed Mode: 150 × 3.0 mm, 2 µm particle, 0.8 mL/min flow, 50:50 water:acetonitrile, 40 °C, 4 µL injection.

Detection combined photodiode array (PDA) at 278 nm and fluorescence (Em 280 nm/Ex 305 nm) to ensure specificity and sensitivity. A mixer (MR 180 µL II) and LabTotal™ vials were employed for consistent mobile phase blending and sample handling.

Used Instrumentation

• Nexera™ lite HPLC system (conventional method)
• Nexera™ XR UHPLC system (high-speed method)
• Shim-pack™ GIST C18 columns (5 µm & 2 µm)
• SPD-M40 PDA detector
• RF-20AXS fluorescence detector

Main Results and Discussion

Both methods achieved baseline separation of IPMP with sharp, symmetric peaks. The high-speed protocol reduced analysis time by approximately 40% while preserving resolution. Peak shape and reproducibility met typical QA/QC acceptance criteria. Dual detection modes facilitated confirmation of analyte identity and improved detection limits.

Benefits and Practical Applications

The described HPLC approaches offer:

• Flexible throughput options for routine or high-throughput laboratories
• Robust performance across column formats
• Simple isocratic mobile phase for ease of use
• Enhanced sensitivity via dual PDA and fluorescence detection

These features support regulatory compliance testing of soaps, cosmetics and related consumer products.

Future Trends and Opportunities

Advancements may include coupling with mass spectrometry for trace-level profiling, adoption of sub-2 µm and core-shell columns for ultra-fast separations, and automated on-line sample preparation. Such innovations will further streamline quality control workflows in the personal care industry.

Conclusion

The developed reversed-phase HPLC methods reliably quantify IPMP in soap matrices. The high-speed variant offers significant time savings without compromising separation quality, making both protocols suitable for regulatory and production environments.

Reference

Application News L586, Shimadzu Corporation, December 2021