4,5-bis(hydroxymethyl)-2-phenyl-1H-imidazole

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 27 January 2022 to 21 March 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Version / remarks:

2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

effusion method: Knudsen cell

Specific details on test material used for the study:

Actual storage conditions: Stored in original plastic bag in a ventilated closed cupboard at normal laboratory temperature.

Temp.:

82.6 °C

Vapour pressure:

< 0.47 Pa

Key result

Temp.:

20 °C

Vapour pressure:

< 0.47 Pa

First Temperature program

Mass loss (mg)	Mass loss duration (s)	Vapour pressure (Pa)	Temperature (K)	1/T (1/K)	Log10 (p)
0.074	600	0.6367	296.85	3.369 x10^-3	-0.1961
0.053	600	0.4586	300.15	3.332 x10^-3	-0.3386
0.044	600	0.3850	307.05	3.257 x10^-3	-0.4145
0.010	600	0.0885	314.15	3.183 x10^-3	-1.0530
0.020	600	0.1791	321.65	3.109 x10^-3	-0.7468

New temperature program (NP)

Mass loss (mg)	Mass loss duration (s)	Vapour pressure (Pa)	Temperature (K)	1/T (1/K)	Log10 (p)
0.018	600	0.1607	319.65	3.128 x10^-3	-0.7939
0.030	600	0.2692	322.85	3.097 x10^-3	-0.5699
0.012	600	0.1096	334.55	2.989 x10^-3	-0.9601
0.014	600	0.1299	344.95	2.899 x10^-3	-0.8866
0.011	600	0.1036	355.75	2.811 x10^-3	-0.9846

Other calculation attempts

Considering the default calculations presented above were not reliable, due to mass losses lower than the accuracy of the balance, and baseline drift, other attempts were made to derive more reliable results:
Calculations without baseline correction led to even lower mass losses for the first program (baseline drift in mass gain), still no trend, and VP ranging between 0.02 and 0.19 Pa. For the NP program, mass losses were still < 50 μg, and VP ranged between 0.29 and 0.36 Pa.

Another try was made using the total mass loss over the whole program (18000 or 18600 s duration), and the lower temperature as the worst-case (actual mass loss higher than if the whole experiment had been performed at the lower temperature, i.e. leading to higher VP) in the equation. This time mass losses were significant. Results were 0.36 and 0.13 Pa at 23.6°C, and 0.17 or 0.31 Pa at 46.4°C, respectively with and without baseline correction.

All results obtained were quite consistent (0.02 to 0.64 Pa) considering the measuring scale of vapour pressure (10^-10 to 10⁺⁵ Pa), but it was not possible to determine an accurate value, due to apparatus and test conditions limitations. The effect of an impurity can’t be excluded either.
Therefore, it was finally decided to calculate a limit value, from the minimum significant mass loss (i.e. 50 μg, accuracy of the balance) that was not achieved even at the higher test temperature for the 10 min isotherm. This gives a vapour pressure of less than 0.47 Pa at 82.6°C.

Executive summary:

The vapour pressure of the test substance was measured according OECD 104 / EU A4 guideline, effusion method with Knudsen cell, and under GLP .
A first experiment was performed between 23.7 and 48.5°C, but the mass losses recorded were not significant compared to baseline. A second program between 46.5 and 82.6°C was tried, but the mass loss observed was still of the same order of magnitude as the baseline mass variation. Moreover the observed mass loss did not correlate with temperature. Attempts for other exploitations did not allow to determine a more accurate vapour pressure either.

Due to technical limitations (degradation of test item at higher temperatures) a limit value was derived, as a worst-case:

Using the Hertz-Knudsen formula with the highest temperature (82.6°C) and a mass-loss corresponding to the precision of the balance (0.05 mg, minimum significant mass loss not attained) gives a vapour pressure of 0.47 Pa. The pressures calculated from the thermograms are thus of the same order of magnitude as the pressure obtained using the precision of the balance.

In conclusion, the vapour pressure of the test item is below 0.47 Pa at 82.6°C, and therefore the vapour pressure at 20°C and 25°C is also below 0.47 Pa.

Description of key information

Could not be measured due to technical limitations. Estimated < 0.47 Pa at 82.6°C, and therefore also < 0.47 Pa at 20°C. (OECD 104, effusion with Knudsen cell, GLP; Noel Y., 2022)