Interference from HONO in the measurement of ambient air NO via photolytic conversion and quantification of NO.

The reference method to quantify mixing ratios of the criteria air pollutant nitrogen dioxide (NO) is NO-O chemiluminescence (CL), in which mixing ratios of nitric oxide (NO) are measured by sampling ambient air directly, and mixing ratios of NO (= sum of NO and NO) are measured by converting NO to NO using, for example, heated molybdenum catalyst or, more selectively, photolytic conversion (P-CL). In this work, the nitrous acid (HONO) interference in the measurement of NO by P-CL was investigated. Results with two photolytic NO converters are presented.

Potential interferences in photolytic nitrogen dioxide converters for ambient air monitoring: Evaluation of a prototype.

Unlabelled: Mixing ratios of the criteria air contaminant nitrogen dioxide (NO) are commonly quantified by reduction to nitric oxide (NO) using a photolytic converter followed by NO-O chemiluminescence (CL). In this work, the performance of a photolytic NO converter prototype originally designed for continuous emission monitoring and emitting light at 395 nm was evaluated. Mixing ratios of NO and NO (= NO + NO) entering and exiting the converter were monitored by blue diode laser cavity ring-down spectroscopy (CRDS).

A compact diode laser cavity ring-down spectrometer for atmospheric measurements of NO3 and N2O5 with automated zeroing and calibration.

A compact rack-mounted cavity ring-down spectrometer (CRDS) for simultaneous measurements of the nocturnal nitrogen oxides NO(3) and N(2)O(5) in ambient air is described. The instrument uses a red diode laser to quantify mixing ratios of NO(3) (at its absorption maximum at 662 nm) and of N(2)O(5) following its thermal dissociation to NO(3) in a second detection channel. The spectrometer is equipped with an automated zeroing and calibration setup to determine effective NO(3) absorption cross-sections and NO(3) and N(2)O(5) inlet transmission efficiencies.