Vapor Pressures of Acetonitrile Determined by Comparative Ebulliometry

Abstract

The vapor pressures of acetonitrile have been measured over the temperature and pressure range of 278 K and 4.3 kPa to 540 K and 4455 kPa. The upper limit exceeds the temperature at which decomposition of acetonitrile begins (about 536 K) so we were able to assess the effect of pyrolysis on the vapor pressures. Acetonitrile is strongly hygroscopic, and a comparison of results obtained with “wet” and “dry” samples allowed us to investigate in a similar way the effect of water as an impurity. The results have been correlated using generalized Wagner equations, a key feature of which is the use of the reversed reduced temperature τ = 1 − T/T c where T c is the critical temperature. The standard form with terms in τ, τ 1.5, τ 2.5, and τ 5 produced unacceptable systematic deviations; but the equation ln(p/p c) = (T c/T)(c 1τ + c 1.5τ1.5 + c 2τ2 + c 2.5τ2.5 + c 5.5τ5.5), where p c is the critical pressure, fits our results from 291 K to 535 K with a standard deviation of 63 × 10-6 in ln p and significantly extends the range of correlation, toward both the triple and critical points, compared with work already in the literature. By extrapolation to T c = 545.46 K, we obtain 4835 kPa for the critical pressure p c and 167 Pa for the triple-point pressure at T s+l+g = 229.35 K. An Antoine equation that describes the results below a pressure of 125 kPa with a standard deviation of 1.5 mK in the condensation temperature has also been obtained.

Rapid Online Non-Enzymatic Protein Digestion Analysis with High Pressure Superheated ESI-MS

“…The reported temperatures that correspond to a vapor pressure of 27atm for methanol and acetonitrile are~180°C and 230°C, respectively [38,39]; thus, in principle, the superheated electrospray should be compatible with conventional or even superheated water eluent capillary liquid chromatography [27,28]. Owing to the large i.d.…”

Vapour pressures of n-hexane determined by comparative ebulliometry

“…At the time, we only measured the vapour pressures of n-hexane down to 41 kPa, although with this same equipment we have since measured vapour pressures as low as 5 kPa and obtained measurements that are of comparable quality to those measured in glass ebulliometers [5][6][7]21]. We have extended the low pressure region down to 13.8 kPa by selecting the vapour pressures measured by Rossini [22] using glass ebulliometers in the comparative mode; we have converted all RossiniÕs temperatures to ITS-90.…”

“…Triple distilled water was used as the reference fluid and helium as the buffer gas. The details of the apparatus have been published before and the reader is referred to the previous articles for a description [5][6][7].…”

“…The great majority of vapour pressures measured by the ebulliometric method have been restricted to pressures below 200 kPa through the use of glass boilers, but work with stainless steel vessels in different laboratories has extended the pressure range considerably in the last decade [4][5][6][7][8][9][10][11]. We report 54 vapour pressures of nhexane over the temperature and pressure range from (315.7 K, 41.1 kPa) to (504.0 K, 2876.8 kPa), which is about 3 K and 150 kPa below the critical point.…”

When API Mass Spectrometry Meets Super Atmospheric Pressure Ion Sources

“…180°C 49) and ca. 230°C, 50) respectively, thus, in principle, HP-ESI is applicable to most LC eluent.…”