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Gregory L. Kok, Scott E. McLaren, and Thomas A. Stafflbach

Abstract

A high-performance liquid chromatographic analytical technique has been developed for the separation of hydrogen peroxide and low molecular weight organic hydroperoxides. A total of 10 C1–C3 organic hydroperoxides have been separated. The detection system is based on postcolumn derivatization using an enzymatic reaction with p-hydroxyphenylacelic acid to form a fluorescent dimer. The detection limit for the technique is 9 × 10−8 M for hydrogen peroxide and 2 × 10−8 M for other hydroperoxides. This paper details the optimization of the analytical technique, examining column characteristics and the chemistry of the analytical reaction.

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Cynthia H. Twohy, Paul J. DeMott, Kerri A. Pratt, R. Subramanian, Gregory L. Kok, Shane M. Murphy, Traci Lersch, Andrew J. Heymsfield, Zhien Wang, Kim A. Prather, and John H. Seinfeld

Abstract

Ice concentrations in orographic wave clouds at temperatures between −24° and −29°C were shown to be related to aerosol characteristics in nearby clear air during five research flights over the Rocky Mountains. When clouds with influence from colder temperatures were excluded from the dataset, mean ice nuclei and cloud ice number concentrations were very low, on the order of 1–5 L−1. In this environment, ice number concentrations were found to be significantly correlated with the number concentration of larger particles, those larger than both 0.1- and 0.5-μm diameter. A variety of complementary techniques was used to measure aerosol size distributions and chemical composition. Strong correlations were also observed between ice concentrations and the number concentrations of soot and biomass-burning aerosols. Ice nuclei concentrations directly measured in biomass-burning plumes were the highest detected during the project. Taken together, this evidence indicates a potential role for biomass-burning aerosols in ice formation, particularly in regions with relatively low concentrations of other ice nucleating aerosols.

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