Temperature dependence of Hg vapour mass concentration at saturation in air: New SI traceable results between 15 and 30°C

There is a need internationally for an agreement on reference values for the calibration of mercury vapour concentration measurements. These reference values are obtained from the relationship between Hg vapour mass concentrations at saturation in air (ɣHg, in ng cm−3) and temperature (T, in K). This relationship was re-evaluated by fitting replicated (n = 3,4) SI traceable measurement results obtained for mL size mercury-saturated air samples at temperatures of around 288.4, 293.3, 298.2 and 303.1 K (2.4%, 0.20%, 0.51% and 1.6% relative standard errors of the means, respectively). It gave ɣHg =C/T*10(−B/T) with B = 3282.92 K and C = 6.73257 × 1014 K ng cm−3, at an estimated relative expanded (combined) uncertainty of 5.9% (k = 2). The measurement procedure was based on temperature controlled automated sampling of the gaseous mercury, isotope dilution of the mercury following trapping into the liquid phase under closed circuit conditions, and inductively coupled plasma mass spectrometry for the signal acquisition.