Rapidly Analyzing Carbonyl Compounds Using HPLC

University of Strasbourg researchers in Strasbourg, France developed a new system for rapidly analyzing 13 carbonyl compounds hydrazones. Their findings were published in the Journal of Chromatography Open (1).

Main building of the university of Strasbourg, France | Image Credit: © dudlajzov - stock.adobe.com

Aldehydes and ketones are organic compounds that incorporate a carbonyl functional group, C=O (2). These compounds are naturally present in fruits and other foods, in soil residues as decomposition products, and can also be formed through reactions between terpenes emitted by foliage with ozone and OH or NO₃ radicals in the atmosphere. Combustion processes from cars create a wide range of molecules, including aldehydes. Traffic is one of the main contributors to ambient air aldehydes. Formaldehyde, widely used as a biocide is used in fields like the health and food industries. Other aldehydes and ketones, such as acetone and butanone, can serve as solvents and chemical intermediates in various manufacturing processes. Formaldehyde has been classified as a carcinogen, with acetaldehyde and acrolein being speculated to be carcinogens as well. There are guidelines and procedures for monitoring these substances, but they can suffer from interference, the researchers wrote (3).

In this study, a new method was proposed for simultaneously analyzing 13 carbonyl compounds, which was adapted for a novel transportable high-performance liquid chromatograph (HPLC) system. With this system, two goals were in mind: i) to develop a robust, transportable HPLC for future on-site analysis of carbonyl compounds in air sampled on DNPH tubes; ii) to develop and validate an ISO 16,000–3-compliant method for quantifying derivatives of 13 carbonyl compounds (including formaldehyde) after reaction with DNPH. The developed method, to the best of the scientists’ knowledge, was the only isocratic method in the literature achieving the separation of 11 of the 13 hydrazones with UV detection in less than 20 min, and with a detection limit below 1 mg L^–1 for formaldehyde-2,4-dinitrophenylhydrazone (FA-DNPH).

The transportable HPLC system was made of a reinforced analytical suitcase and a computer suitcase, both of which came with spring systems to fortify them against impact. The system also features a straightforward isocratic pump, ensuring reliability and ease of operation, while sample delivery is managed by a piston pump coupled to a multiplexing valve. Derived carbonyl compounds with 2,4-dinitrophenylhydrazine were separated in isocratic mode using water and acetonitrile. Using a reverse-phase column, the process was completed in less than 20 minutes. Out of the 13 hydrazones, only 2-butanone-2,4-DNPH (BO-DNPH) and butanal-2,4-DNPH (BA-DNPH) were fully coeluted, and separation of the other critical pairs containing 3 and 4 carbons was achieved. Afterwards, the method was applied to the transportable HPLC system equipped with an ultraviolet (UV) or light-emitting diode (LED) detector. These findings were then compared with the results obtained on two benchtop laboratory HPLCs equipped with a diode array detector (DAD).

The limit of detection (LOD) for the carbonyl compounds’ hydrazones ranged from 0.12 to 0.38 mg L^–1 with the UV detector and 0.45 to 1.04 mg L^–1 with the LED detector. Precision was determined from consecutive injections of the analytes to yield RSD < 11.5% (UV) and RSD < 14.1% (LED). The performances were close to those of the laboratory HPLCs, either in sensitivity, resolution, or repeatability with overall more accurate and robust results with the UV than with the LED detector. In spite of the LED system not fully meeting standard method requirements with linearities correlation coefficients lower than 0.999, both systems and methods were validated for the isocratic analysis of hydrazones for aldehyde and ketone quantification. Further, additional comparisons were made with the literature regarding the isocratic method developed and the transportable system.

While the LED detector is not optically complex, it can be considered more robust than the UV detectors. Improvements can be made to make the system achieve similar performances to other HPLCs. The scientists admit their system may be comparatively heavy in contrast to miniaturized counterparts weighing a few kilograms, the new format enhances portability, robustness in challenging conditions of transportation and fast set-up. Future work will involve modifying the sample delivery system to perform automatic elution.

References

(1) Grandjean, A.; Becker, A.; Mascles, M.; et al. Development of a Transportable High-Performance Liquid Chromatograph with Ultraviolet Detection and a Method for the Rapid Analysis of 13 Carbonyl Compounds Hydrazones. J. Chromatogr. Open 2025, 7, 100201. DOI: 10.1016/j.jcoa.2024.100201

(2) Aldehydes and Ketones. Michigan State University 2013. https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/aldket1.htm (accessed 2025-4-18)

(3) Bunkoed, O.; Davis, F.; Kanatharana, P.; et al. Sol–Gel Based Sensor for Selective Formaldehyde Determination. Anal. Chim. Acta 2010, 659 (1–2), 251–257. DOI: 10.1016/j.aca.2009.11.034