Surface analysis of particulates from laboratory hood exhaust manifold

Abstract

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 − , NO 3 − , and HSO 4 − , 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

Atomic spectrometry update. Atomic mass spectrometry

“…The fundamental requirement for double spiking is to have a spike that is very different in isotopic composition to the samples being analysed. Whereas highly enriched 204 Pb and 207 Pb spikes are normally used for the analysis of common lead, the NIST common lead SRM 981 and 982 have been used as spikes for the analysis of highly radiogenic samples such as zircons. 254 Although the method had the advantage of using well-characterized SRM and was considered to be viable, it was not universally applicable and did not provide better performance than established procedures.…”

“…In contrast to ns-LA, this fs-LA system produced unfractionated U:Th and Pb:U elemental ratios and Fe-isotope measurements free of mass bias other than that produced by the MC-ICP-MS instrument itself. The precisions for 207 Pb: 206 Pb and 206 Pb: 238 U were 0.03 and 0.2% (2 RSD), respectively. The precision obtained for the d 56 Fe was 0.1& (2 SD), which was close to that obtainable by solution MC-ICP-MS. Elemental fractionation was absent even when using different LA protocols such as comparing spots versus raster lines.…”

“…Monoatomic and polyatomic projectiles have been compared for the speciation and quantification of particulate samples collected from a laboratory ventilation manifold. 207 Specifically, 12 keV Ga + and 5.35 keV polyatomic ReO 4…”

“…A dry aerosol of NIST SRM 981 was introduced at the same time as a xylene blank and then a blank dry aerosol was introduced with the crude oil sample. Replicate measurements (n ¼ 10) of organic samples containing 10 ng g À1 Pb gave precisions better than 0.2% for Pb: 207 Pb, 208 Pb: 206 Pb, 206 Pb: 207 Pb, and 0.5% for 206 Pb: 204 Pb, 207 Pb: 204 Pb, 208 Pb: 204 Pb. Isotope ratios measured by this method for two different crude oils were in good agreement with results from samples that had been digested prior to aqueous analysis.…”

“…A 207 Pb- 204 Pb double-spike MC-ICP-MS technique for Pb isotope analysis without Tl addition overcame inherent problems of differing mass bias correction factors for Pb and Tl and variable oxidation of Tl during desolvation. 157 The precisions for measurement of the 206 Pb: 204 Pb, 207 Pb: 204 Pb and 208 Pb: 204 Pb ratios in a 50 ng ml À1 solution of NIST SRM 981 (equivalent to consumption of 11 ng Pb) were in the range 0.002-0.003% (RSD, n ¼ 35) and consistent with previous TIMS and MC-ICP-MS studies. Use of lower Pb consumptions (4 ng and 20 pg) resulted in poorer precisions of 0.007-0.009 and 0.3-0.7%, respectively.…”