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Nitrophenols (NPs), having effects to human health, are produced in atmosphere via several pathways. However behavior details of atmospheric NPs are not well understood. In this work, daily variations of NPs were investigated by repeating 2-h collection using silica gel columns followed by HPLC/MS analysis. Collection method was optimized and large volume injection and in-line preconcentration was automated for the HPLC analysis. Quantification limits by atmospheric pressure chemical ionization mass analysis for each atmospheric NP ranged between 0.08 and 0.67 ng m–3 with time resolution of 2 h. Clear daily variations were obtained by this method. Whereas NP concentrations were high around noon in summer, they were maxima before midnight in winter. This was likely due to difference of main mechanism for NP formations: mainly OH radical and NO3 radical initiated the formation reaction in summer and winter, respectively. In winter, total NP concentration was higher than in summer especially 2-nitrophenol which accounted for a half of all NPs measured. On the contrary, formation of dinitrophenol from mononitrophenol seemed to proceed abundantly in summer. Also seasonal variation was obtained from rain water analysis and filter sampling. Concentrations and partition of NPs were different with difference of polarity and reactivity. It was considered that NP concentrations changed dynamically in atmosphere via secondary production and reactions to disappear.ニトロフェノール類NPsは健康リスクのある化合物として知られておりまた大気中で様々な経路により生成するがその実態はあまり知られていない本研究ではシリカゲル充填チューブに2時間ごとに捕集したNPsを高速液体クロマトグラフィー/質量分析法HPLC/MSにて分析を行い日内変動の解析を試みた捕集法の検討やHPLCへの大容量注入濃縮の自動化をはかり各種NPの分析が可能になった検出には大気圧イオン化質量分析を用いた2時間捕集による大気中各種NPの定量下限は0.080.67 ng m3の範囲であった本法により日内変動を調べたところ夏は日中に濃度が高くなりまた冬は夜半前に高濃度になり季節で異なった日内変動パターンが得られたこれは季節により支配的となる二次的生成機構が異なったためと考えられるすなわち夏季はOHラジカル冬季はNO3ラジカルに起因する反応に依存していると考えられるまた冬季のNP総濃度は夏より高濃度となり特に2-nitorophenolが約半分を占めた逆に夏はモノニトロフェノールのジニトロ化の進行が示唆された雨水に含まれるNPsやフィルターに捕集されたNPsについても分析を行ったところ大気中NO2の増減と同じような季節変動を示した一連の分析結果から各種NPの存在状態は極性や反応性によってそれぞれ異なっておりまた大気中で二次的な生成や消失を繰り返しながら大きく濃度変動していることが示された

Investigation of Daily Variation of Atmospheric Nitrophenols by Means of Inline Preconcentration-HPLC/MS Analysis with Large Volume Injection