Rot

Time (EDT)

FIGURE 11.8 Ambient H202 concentrations measured by TDLS (•) and the continuous scrubbing enzyme fluorometric technique (□) during the period June 24-26 at Research Triangle Park, North Carolina (adapted from Schiff et al, 1994a, 1994b).

Time (EDT)

FIGURE 11.8 Ambient H202 concentrations measured by TDLS (•) and the continuous scrubbing enzyme fluorometric technique (□) during the period June 24-26 at Research Triangle Park, North Carolina (adapted from Schiff et al, 1994a, 1994b).

transition. The low temperature of the matrix, lack of diffusion in the matrix, and the isolation of trapped molecules also help to minimize decomposition and other reactions of labile species.

This approach has also been used in the analysis of air by infrared spectroscopy (e.g., see Griffith, f 994). As discussed later, matrix isolation has also been used in conjunction with electron spin resonance (ESR) to measure free radical species, including N02, N03, H02, and ROz.

In the matrix-FTIR studies, about 10-80 L of air is typically trapped using either a liquid nitrogen or liquid argon trap. At these temperatures, N2, 02, H2, CH4, and CO are not trapped, but C02 and trace gases are. The C02 in air acts as the inert matrix material when the sample is condensed on the infrared sample stage

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