Uncertainty models and influence of the calibration span on ambient air measurements of NO2 by chemiluminescenceElectronic supplementary information (ESI) available. See DOI: 10.1039/c2em30395g

• Main Authors: Miñarro, Marta Doval, Ballesta, Pascual Pérez, Rico, Jonathan Barberá, Ferradás, Enrique González
• Format: Journal Article
• Language: English
• Published: 30.01.2013
• DOI: 10.1039/c2em30395g
• ISSN: 2050-7887

An assessment of uncertainty in the hourly and annual limit values of NO 2 measurements by molybdenum NO 2 -to-NO conversion followed by chemiluminescence detection was carried out at 3 different span concentrations (100, 300 and 700 nmol mol −1 ). The uncertainty of the linearity term was calculated for each span concentration by considering (i) a zero-and-span calibration and (ii) a multipoint calibration. Two uncertainty models were applied for the overall uncertainty estimation: (i) the Standard EN 14211 and (ii) a mechanistic model that considers the NO 2 reduction in the converter. The main difference between these models stems from considering or not the possible covariances derived from interactions between NO x and NO concentrations and the converter's efficiency. For both models, the span determined whether or not it was possible to meet the quality objective requested by the EU Air Quality Directives in the annual limit value when no linearity corrections were performed in environments with NO z /NO 2 ratios ≤ 0.04. In environments with significant amounts of NO z species (NO z /NO 2 ≥ 0.12), the expanded uncertainty can easily be higher than the data quality objective if bias' corrections are not or cannot be applied. Uncertainty assessment of NO 2 chemiluminescence measurements via two uncertainty models with three different span concentrations in two different types of environments.