Simultaneous Analysis of DNPH-Derivatized Aldehydes Using Prominence™-i Plus and Shim-pack Scepter™ PFPP-120

Importance of the Topic

This study addresses the need for reliable measurement of six aldehydes designated under Japan’s Offensive Odor Control Law. Accurate monitoring of acetaldehyde, propionaldehyde, n-butyraldehyde, iso-butyraldehyde, n-valeraldehyde and iso-valeraldehyde at emission points is essential for environmental compliance and public health protection. Derivatization with 2,4-dinitrophenylhydrazine (DNPH) combined with high-performance liquid chromatography (HPLC) provides the sensitivity and selectivity required for low-level odor-intensity determination.

Goals and Overview of the Study

The primary objective was to demonstrate a simultaneous HPLC method for quantitative separation of DNPH-derivatized aldehydes using Shimadzu’s Prominence-i Plus integrated HPLC and the Shim-pack Scepter PFPP-120 column. Key aims included:

• Achieving baseline separation of six DNPH derivatives, including structural isomers.
• Establishing linear calibration curves across relevant concentration ranges.
• Validating limits of detection (LOD), limits of quantitation (LOQ) and repeatability.

Methodology and Instrumentation

DNPH-derivatized aldehyde standards were prepared in acetonitrile. Chromatographic separation was performed under gradient elution with water (A) and methanol/acetonitrile 8:2 (B), using a 150 × 4.6 mm, 3 µm PFPP column at 35 °C. The gradient program increased B from 20 % to 60 % over 25 min, then returned to initial conditions. Injection volume was 20 µL, flow rate 1.0 mL/min, and detection at 360 nm (D₂ lamp).

Used Instrumentation

• Prominence-i Plus integrated HPLC system (Shimadzu)
• Shim-pack Scepter PFPP-120 column (150 mm × 4.6 mm I.D., 3 µm)
• UV detector at 360 nm

Main Results and Discussion

Simultaneous analysis yielded clear peaks for all six DNPH derivatives with resolution values of 1.40–2.00 for structural isomers. Calibration curves over 0.05–10 µg/mL returned correlation coefficients (R²) ≥ 0.9999. For the lowest-standard analyte (iso-valeraldehyde), the LOQ was 0.0052 µg/mL and the LOD 0.0017 µg/mL. Relative errors at LOQ were within ±5 % and repeatability (%RSD, n=6) under 1 % for all analytes. Results were consistent when using either the low-pressure gradient integrated system or a high-pressure modular gradient HPLC.

Benefits and Practical Applications

This method enables simultaneous quantitation of six odor-regulated aldehydes in a single run, reducing analysis time and labor. High sensitivity and reproducibility meet regulatory requirements for odor intensity monitoring. The robust PFPP column chemistry offers enhanced isomer separation, valuable for environmental laboratories, process monitoring and regulatory compliance.

Future Trends and Possibilities

Emerging improvements may include ultrahigh-pressure LC with sub-2 µm PFPP phases for faster separations, on-site and portable HPLC platforms for real-time odor assessment, and advanced derivatization reagents to broaden analyte scope. Integration with automated sampling and data analytics will further streamline environmental monitoring and quality control.

Conclusion

The study confirms that the Prominence-i Plus integrated HPLC coupled with a PFPP-120 column reliably separates and quantifies six DNPH-derivatized aldehydes at regulatory levels. High linearity, low detection limits and excellent repeatability support routine application in odor-intensity compliance assays under Japan’s Offensive Odor Control Law.

Reference

Notification of partial revision of the measurement method for Specified Offensive Odor Substances (September 2018, Ministry of the Environment Notification No. 78)