National Institute for Occupational Safety and Health, NIOSH Manual of Analytical Methods… (1994)
“ During the development of the passive monitor method for ammonia (6701) , sulfuric acid-treated silica gel tubes were used as one of the reference methods [5] . The silica gel samples with IC analysis showed good agreement with the other reference methods, bubbler collection with colorimetric analysis using Nessler’s Reagent, and bubbler collection with IC analysis. A storage stability study compared the sulfuric acid-treated silica gel tube and sulfuric acid-treated carbon beads used in OSHA Method ID-188. ”
