Aix Marseille Univ, CNRS, LCE, Marseille, France; Aix Marseille Univ, CNRS, ICR, Marseille, France.
Aix Marseille Univ, CNRS, LCE, Marseille, France; Aix Marseille Univ, CNRS, ICR, Marseille, France; Aix Marseille Univ, CNRS, MIO, Marseille, France.
Chemosphere. 2023 Apr;319:137977. doi: 10.1016/j.chemosphere.2023.137977. Epub 2023 Feb 1.
Among the highly oxygenated species formed in situ in the atmosphere, α-dicarbonyl compounds are the most reactive species, thus contributing to the formation of secondary organic aerosols that affect both air quality and climate. They are ubiquitous in the atmosphere and are easily transferred to the atmospheric aqueous phase due to their high solubility. In addition, α-dicarbonyl compounds are toxic compounds found in food in biochemistry studies as they can be produced endogenously through various pathways and exogenously through the Maillard reaction. In this work, we take advantage of the high reactivity of α-dicarbonyl compounds in alkaline solutions (intramolecular Cannizzaro reaction) to develop an analytical method based on high performance ion chromatography. This fast and efficient method is suitable for glyoxal, methylglyoxal and phenylglyoxal which are detected as glycolate, lactate and mandelate anions respectively, with 100% conversion at pH > 12 and room temperature for exposure times to hydroxide ranging from 5 min to 4 h. Diacetyl is detected as 2,4-dihydroxy-2,4-dimethyl-5-oxohexanoate due to a base-catalysed aldol reaction that occurs before the Cannizzaro reaction. The analytical method is successfully applied to monitor glyoxal consumption during aqueous phase HO∙-oxidation, an atmospherically relevant reaction using concentrations that can be observed in fog and cloud water. The method also reveals potential analytical artifacts that can occur in the use of ion chromatography for α-hydroxy carboxylates measurements in complex matrices due to α-dicarbonyl conversion during the analysis time. An estimation of the artifact is given for each of the studied α-hydroxy carboxylates. Other polyfunctional and pH-sensitive compounds that are potentially present in environmental samples (such as nitrooxycarbonyls) can also be converted into α-hydroxy carboxylates and/or nitrite ions within the HPIC run. This shows the need for complementary analytical measurements when complex matrices are studied.
在大气中就地形成的高度含氧物种中，α-二羰基化合物是最具反应性的物种，因此有助于形成影响空气质量和气候的二次有机气溶胶。它们在大气中无处不在，由于其高溶解度，很容易转移到大气水相。此外，α-二羰基化合物是生物化学研究中食品中的有毒化合物，因为它们可以通过各种途径内源性产生，也可以通过美拉德反应外源性产生。在这项工作中，我们利用α-二羰基化合物在碱性溶液中的高反应性（分子内 Cannizzaro 反应），开发了一种基于高效离子色谱的分析方法。这种快速有效的方法适用于乙二醛、甲基乙二醛和苯乙二醛，它们分别被检测为甘醇酸盐、乳酸盐和扁桃酸盐阴离子，在 pH>12 和室温下，100%转化率，暴露于氢氧化物的时间从 5 分钟到 4 小时不等。二乙酰基被检测为 2,4-二羟基-2,4-二甲基-5-氧代己酸酯，因为在 Cannizzaro 反应之前发生了碱催化的醛醇缩合反应。该分析方法成功应用于监测水相中 HO·-氧化过程中乙二醛的消耗，HO·-氧化是一种与大气相关的反应，使用的浓度可以在雾和云水中观察到。该方法还揭示了在使用离子色谱法分析复杂基质中的α-羟基羧酸时可能出现的潜在分析假象，因为在分析过程中α-二羰基化合物会发生转化。对所研究的α-羟基羧酸酯中的每一种都给出了分析假象的估计。其他多官能团和 pH 敏感的化合物，如亚硝酰基，也可能在 HPIC 运行过程中转化为α-羟基羧酸酯和/或亚硝酸盐离子。这表明在研究复杂基质时需要进行补充分析测量。
