Department of Chemistry, University of North Dakota, 151 Cornell Street, Grand Forks, ND 58202, USA; Restek, 110 Benner Circle, Bellefonte, PA 16823, USA.
Department of Chemistry, University of North Dakota, 151 Cornell Street, Grand Forks, ND 58202, USA; Spectrum Health, 25 Ottawa Ave SW, Grand Rapids MI 49503, USA.
J Chromatogr A. 2018 Apr 6;1544:49-61. doi: 10.1016/j.chroma.2018.02.026. Epub 2018 Feb 18.
Carboxylic acids and aldehydes are present in ambient air particulate matter (PM) originating from both primary emission and secondary production in air and may, due to their polarity have, an impact on formation of cloud condensation nuclei. Their simultaneous determination may provide improved understanding of atmospheric processes. We developed a new analytical method allowing for a single step determination of majority of carboxylic acids and aldehydes (+95 compounds). This sample preparation employed O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA·HCl) in methanol to yield oximes (for aldehydes) and methyl esters (for majority of acids); with the limits of detection of 0.02-1 ng per injection, corresponding to approximately 0.4-20 μg/g. Subsequent trimethylsilylation with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) was employed only for aromatic acids, which were not completely esterified, and for hydroxyl groups. Our method, in contrast to previous primarily qualitative studies, based on derivatization with an aqueous PFBHA followed by BSTFA derivatization, is less labor-intesive and reduces sample losses caused by an evaporation. The method was tested with a broad range of functionalized compounds (95), including monocarboxylic, dicarboxylic and aromatic acids, ketoacids, hydroxyacids and aldehydes. The developed protocol was applied to wood smoke (WS) and urban air standard reference material 1648b (UA) PM. The observed concentrations of aldehydes were 10-3000 μg/g in WS PM and 10-900 μg/g in UA PM, while those of acids were 20-1800 μg/g in WS PM and 15-1200 μg/g in UA PM. The most prominent aldehydes were syringaldehyde and vanillin in WS PM and glyoxal in UA PM. The most abundant acids in both PM samples were short-chain dicarboxylic acids (≤C). WS PM had a high abundance of hydroxyacids (vanillic and malic acids) as well as ketoacids (glutaric and oxalacetic) while UA PM also featured a high abundance of long-chain monocarboxylic acids (≥C).
羧酸和醛存在于大气颗粒物（PM）中，这些颗粒物来源于初级排放和空气中的二次生成，由于其极性，可能会影响云凝结核的形成。同时测定它们可以更好地了解大气过程。我们开发了一种新的分析方法，可以一步测定大多数羧酸和醛（+95 种化合物）。这种样品制备方法使用甲醇中的 O-(2,3,4,5,6-五氟苄基)羟胺（PFBHA·HCl）生成肟（用于醛）和甲酯（用于大多数酸）；检测限为 0.02-1ng/注射，相当于约 0.4-20μg/g。随后仅对未完全酯化的芳族酸和羟基进行 N,O-双（三甲基硅基）三氟乙酰胺（BSTFA）的三甲基硅烷化。与以前主要基于衍生化的定性研究不同，我们的方法使用与水合 PFBHA 衍生化后与 BSTFA 衍生化的方法相比，劳动强度较低，并且减少了由于蒸发而导致的样品损失。该方法用广泛的功能化化合物（95 种）进行了测试，包括单羧酸、二羧酸和芳香酸、酮酸、羟基酸和醛。所开发的方案应用于木烟（WS）和城市空气标准参考物质 1648b（UA）PM。在 WS PM 中观察到的醛浓度为 10-3000μg/g，在 UA PM 中为 10-900μg/g，而在 WS PM 中观察到的酸浓度为 20-1800μg/g，在 UA PM 中为 15-1200μg/g。在 WS PM 中最突出的醛是丁香醛和香草醛，在 UA PM 中是乙二醛。在这两种 PM 样品中含量最丰富的酸都是短链二羧酸（≤C）。WS PM 中羟基酸（香草酸和苹果酸）和酮酸（戊二酸和草酰乙酸）含量很高，而 UA PM 中长链单羧酸（≥C）含量也很高。
