Measurement of ambient hydroperoxides using an automated HPLC system and various factors which affect variations of...

An HPLC system was automated for the measurement of gaseous hydroperoxides in the ambient air. In this system, samples collected using a glass coil without a long sampling tube are injected automatically into HPLC. The analytical system is based on the post-column derivatization, which is a reaction of hydroperoxides with p-hydroxyphenyl acetic acid to produce a fluorescent dimer in the presence of horseradish peroxidase as an enzyme catalyst. The detection limits of hydrogen peroxide (H(2)O(2)) were from 0.018 to 0.042 ppbv. The gaseous hydroperoxides were measured in Gwangju during March, May and October 2002, and in Seoul during June 2002. H(2)O(2) concentrations were remarkably low and almost at the detection limit during a period of the yellow sand (Asian dust). These results might be strongly ascribed to the effect of Asian dust particles for heterogeneous loss of peroxides and partly loss of samples due to the storage of sample and analysis. Methyl hydroperoxide (CH(3)OOH) was identified and quantified only in Seoul. The highest concentrations of H(2)O(2) were 0.24, 2.84, and 0.89 ppbv during March, May, October, respectively in Gwangju, and 5.19 ppbv in Seoul. The concentration of CH(3)OOH was as high as 1.1 ppbv and sometimes its concentration was higher than that of H(2)O(2) in the early morning or in the late night. The variability of CH(3)OOH was lower than that of H(2)O(2). H(2)O(2) showed a positive relationship with O(3) (r = 0.54, P < 0.01 level; two-tailed), solar radiation (r = 0.61, P < 0.01 level; two-tailed), temperature (r = 0.66, P < 0.01 level; two-tailed), and a negative relationship with NO( x ) (r = -0.20, P < 0.05 level; two-tailed), and relative humidity (r = -0.58, P < 0.01 level; two-tailed) in Seoul. Thus, photochemical activity is considered an important factor in gaseous H(2)O(2) and CH(3)OOH distribution.