title: Reference materials at emission levels of NH3 and HCl.
abstract: Due to instability in static mixtures, in the past only dynamic preparation techniques for mixtures of NH3 and HCl were maintained; however, recent developments of new passivation techniques for cylinder treatment and commercially available nitrogen with a very low content of impurities have opened up the possibility of preparing stable mixtures in cylinders by gravimetry. Mixtures of NH3 (300 microL/L and 30 microL/L) and HCI (300 microL/L) were prepared in nitrogen in cylinders with different passivation treatments. The mixtures were compared with dynamically prepared mixtures using Photo Acoustic detection (PAS) and FT-IR. The uncertainty is about 3.5% with PAS analysis for NH3 at the 300 microL/L level. For the analysis of HCI with FT-IR the initial uncertainty in the 300 microL/L mixtures is about 7%. Two of the HCI mixtures show significant instability; for the other three mixtures the uncertainty in the measurement is too large to discriminate between stability and instability. The NH3/N2 mixtures are stable within 3.5% for a one-year period. The stability of the 30 microL/L mixtures of NH3 cannot be underpinned by measurement results, but a systematic effect in the measurement procedure seems more likely than instability. Improvement in the measurement procedure should clarify this point.
authors.affiliation: Nederlands Meetinstituut, Delft, The Netherlands. JvanWijk@NMi.nl
authors.forename: J I
authors.initials: JI
authors.lastname: van Wijk
authors.forename: G
authors.initials: G
authors.lastname: Nieuwenkamp
authors.forename: T L
authors.initials: TL
authors.lastname: Hafkenscheid
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000592:standards; D000641:Ammonia / Q000032:analysis / Q000592:standards*; D004784:Environmental Monitoring / Q000379:methods / Q000592:standards*; D006851:Hydrochloric Acid / Q000032:analysis / Q000592:standards*; D012015:Reference Standards
chemical_list: D000393:Air Pollutants; D000641:Ammonia; D006851:Hydrochloric Acid