Surface analysis of particulates from laboratory hood exhaust manifold

摘要

Particulate samples collected from a laboratory ventilation manifold during routine maintenance were analyzed to determine if particulate composition had changed as a result of changes in the laboratory's atmosphere. This ventilation manifold exhausts more than 100 fume hoods. The particulate samples were analyzed using static secondary ion mass spectrometry (SIMS). The negative SIMS spectra showed abundant Cl-, NO3-, and HSO4-, consistent with the use of mineral acids in the laboratory. Cluster anions containing primarily Zn (but also other transition metals) were detected, which signaled corrosion of the manifold's galvanized steel by the volatilized acids. The most abundant ions in the cation SIMS spectra were derived from cyclohexylamine (CHA), which had been used as an antiscaling agent in the facility's boiler. Steam from the boiler, which contained CHA, was used to humidify the building air, this practice stopped in 1997. The abundances of the CHA-derived ions were significantly lower in the samples collected in 2004 and 2006 than in the 1992 samples, indicating that the CHA is being slowly depleted. Changes in the relative abundances suggest exponential depletion from the manifold with rate constants that are on the order of 0.01 to 0.04 month(-1). Published in 2007 by John Wiley &. Sons, Ltd.