Evaluation of the Performance of DNPH-Coated Silica Gel and C18 Cartridges in the Measurement of Formaldehyde in the Presence and Absence of Ozone

Abstract

Formaldehyde (HCHO) is an important photochemical product generated during the oxidation of volatile organic compounds in the troposphere. Accurate HCHO concentrations are essential for developing a quantitative basis for ozone formation and represent a primary monitoring objective for the Photochemical Assessment and Monitoring Stations (PAMS). In the PAMS network, measurements of HCHO are conducted by a derivatization method using cartridges coated with 2,4-dinitrophenylhydrazine (DNPH). In this study, a manifold system has been designed to evaluate the performance, accuracy, and importance of interfer ences of DNPH-coated silica gel and C18 cartridges using gas-phase calibration standards. Compared to the independent gas-phase calibration values, HCHO values from silica gel cartridges were typically 5% lower than the reference values over the range of 2−25 ppbv; C18 cartridge values were systematically lower by 20%. These results were found to be independent of the level of humidity in the system. The ...