Measurement of atmospheric hydroxyacetone, glycolaldehyde, and formaldehyde.
Measurement of atmospheric hydroxyacetone, glycolaldehyde, and formaldehyde.
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DOI：
10.1021/es803025g
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发表时间：
2009-03
影响因子：
11.4
通讯作者：
Xianliang Zhou;Gu Huang;K. Civerolo;J. Schwab
中科院分区：
文献类型：
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作者：
Xianliang Zhou;Gu Huang;K. Civerolo;J. Schwab
基于使用盘管进样器进行水洗，然后进行 DNPH 衍生化和 HPLC 分析，对羟基丙酮以及甲醛和乙醇醛的测量方法进行了修改和优化。研究了衍生化平衡和动力学以优化羟基丙酮-DNPH 衍生物的产率。研究发现，该方法对羟基丙酮的灵敏度较低是由于羟基丙酮-DNPH衍生反应的平衡常数相对较小，因此可以通过增加DNPH试剂浓度来改善。在含有 500 µM DNPH 和 50 mM HCl 的介质中，衍生化在 30 分钟内达到平衡。使用 DNPH 饱和 Sep-Pak C-18 柱的在线试剂纯化程序有效去除了 DNPH 试剂溶液中的腙杂质，使用 C-18 保护柱的样品预浓缩程序大大提高了灵敏度并降低了检测限。在优化条件下，系统对羟基丙酮、乙醇醛和甲醛的检测下限分别为 30、9 和 36 pptv，采样/分析周期时间为 30 分钟。该方法已于 1998 年夏天在纽约州艾迪生 Pinnacle 州立公园的一个乡村地点成功部署了 5 周。羟基丙酮、乙醇醛和甲醛的环境浓度平均值（中位数）分别为 372 (332)、301 (323) 和 2040 (2030) pptv。所有三种羰基化合物的日浓度分布均观察到下午晚些时候的最大值和清晨的最小值。三种羰基化合物之间良好的相关性表明它们源自共同来源，即生物碳氢化合物的光化学氧化。甲醛光解约占自由基光产生总量的 23%，而羟基丙酮和乙醇醛光解的贡献微不足道，因为这些化合物的光解速度慢得多且浓度较低。
A method has been modified and optimized for the measurements of hydroxyacetone as well as formaldehyde and glycolaldehyde, based on aqueous scrubbing using a coil sampler followed by DNPH derivatization and HPLC analysis. Derivatization equilibrium and kinetics were studied to optimize the hydroxyacetone-DNPH derivative yield. It was found that the low sensitivity of hydroxyacetone by this method is due to a relatively small equilibrium constant for the hydroxyacetone-DNPH derivatization reaction, and thus it can be improved by increasing DNPH reagent concentration. In a medium containing 500 microM DNPH and 50 mM HCl, the derivatization reaches equilibrium within 30 min. An online reagent purification procedure using a DNPH-saturated Sep-Pak C-18 cartridge effectively removed hydrazone impurities in the DNPH reagent solution, and a sample preconcentration procedure using a C-18 guard column greatly enhanced the sensitivity and lowered the detection limits. The lower detection limits of the system under optimized conditions are 30, 9, and 36 pptv for hydroxyacetone, glycolaldehyde, and formaldehyde, respectively, with a sampling/analysis cycle time of 30 min. The method has been successfully deployed at a rural site in Pinnacle State Park in Addison, NY, for a 5 week period during the summer of 1998. The ambient concentration means (medians) were 372 (332), 301 (323), and 2040 (2030) pptv for hydroxyacetone, glycolaldehyde, and formaldehyde, respectively. A late-afternoon maximum and an early morning minimum were observed in the diurnal concentration distributions of all three carbonyl compounds. Good correlations among the three carbonyl compounds suggest that they originated from a common source, i.e., photochemical oxidation of biogenic hydrocarbons. Formaldehyde photolysis accounted for about 23% of the total radical photoproduction, whereas contributionsfrom hydroxyacetone and glycolaldehyde photolysis were insignificant because of the much slower photolysis and lower concentrations of these compounds.