Cell coatings to minimize sample (NH_3 and N_2H_4) adsorption for low-level photoacoustic detection

Abstract

A photoacoustic signal rise time technique is used to evaluate the suitability of several surface materials for minimizing sample adsorption loss in a trace level toxic vapor monitor. Four materials, 304 stainless steel, gold, paraffin wax, and Teflon, are tested using ammonia as a sample. Teflon is also tested using hydrazine. Results show that both metals interact strongly with the sample. Teflon coating is found to provide the resonant photoacoustic cell with accurate real time response for both hydrazine and ammonia sample flows.