A fast and efficient method for the analysis of α-dicarbonyl compounds in aqueous solutions: development and application

authors

• Brun Nicolas
• González-Sánchez Juan Miguel
• Demelas Carine
• Clément Jean-Louis
• Monod Anne

keywords

• Analytical chemistry
• Atmospheric chemistry
• Fogs and clouds chemistry
• Α-dicarbonyls
• High-Performance Ion Chromatography
• MS Mass Spectrometry ECD Electron Capture Detector GC Gas Chromatography FID Flame Ionisation Detector UV UV
• MS Mass Spectrometry
• ECD Electron Capture Detector
• GC Gas Chromatography
• FID Flame Ionisation Detector
• UV UV

document type

abstract

Among the highly oxygenated species formed in situ in the atmosphere, α-dicarbonyl compounds are the most reactive species, 13 thus contributing to the formation of secondary organic aerosols that affect both air quality and climate. They are ubiquitous 14 in the atmosphere and are easily transferred to the atmospheric aqueous phase due to their high solubility. In addition, α-15 dicarbonyl compounds are toxic compounds found in food in biochemistry studies as they can be produced endogenously 16 through various pathways and exogenously through the Maillard reaction. In this work, we take advantage of the high reactivity 17 of α-dicarbonyl compounds in alkaline solutions (intramolecular Cannizzaro reaction) to develop an analytical method based 18 on high performance ion chromatography. This fast and efficient method is suitable for glyoxal, methylglyoxal and 19 phenylglyoxal which are detected as glycolate, lactate and mandelate anions respectively, with 100% conversion at pH > 12 20 and room temperature for exposure times to hydroxide ranging from 5 minutes to 4 h. Diacetyl is detected as 2,4-dihydroxy-21 2,4-dimethyl-5-oxohexanoate due to a base catalysed aldol reaction that occurs before the Cannizzaro reaction. The analytical 22 method is successfully applied to monitor glyoxal consumption during aqueous phase HO∙ oxidation, an atmospherically 23 relevant reaction using concentrations that can be observed in fog and cloud water. The method also reveals potential analytical 24 artifacts that can occur in the use of ion chromatography for α-hydroxy carboxylates measurements in complex matrices due 25 to α-dicarbonyl conversion during the analysis time. An estimation of the artifact is given for each of the studied α-hydroxy 26 carboxylates. Other polyfunctional and pH-sensitive compounds that are potentially present in environmental samples (such 27 as nitrooxycarbonyls) can also be converted into α-hydroxy carboxylates and/or nitrite ions within the HPIC run. This shows 28 the need for complementary analytical measurements when complex matrices are studied.

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