Negative interference of Teflon sampling devices in the determination of nitric acid and particulate nitrate.
A laboratory study was performed to evaluate the transmission of nitric acid through different materials. Copper, stainless steel, sodium glass and chromium-plated stainless steel proved to be poor choices for the construction of size classifiers, transfer lines and filter holder plates of air sampling devices, as they adsorb significant amounts of nitric acid. Tubes made of Teflon or pyrex exhibited good HNO3 transmission but, unexpectedly, devices machined from Teflon rods (cyclones, manifolds) showed a noticeable sorption capacity. Moreover, the Teflon of different manufacturers behaved differently. The features of a sampling unit capable of accurate measurements of nitric acid and ammonium nitrate in the atmosphere are discussed.
De Santis
F
F
Istituto sull'Inquinamento Atmosferico, C.N.R., Area della Ricerca di Roma, Monterotondo Stazione, Italy.
Febo
A
A
Perrino
C
C
D008722:Methods; D009566:Nitrates / Q000032:analysis*; D017942:Nitric Acid; D011138:Polytetrafluoroethylene
D009566:Nitrates; D017942:Nitric Acid; D011138:Polytetrafluoroethylene