Reaction mass of 2-ethylhexyl (6-isocyanatohexyl)-carbamate and bis(2-ethylhexyl) 1,6-hexan-1,6-diylbiscarbamate

Hydrolysis

Description of key information

The tests were performed based on OECD Guidelines for Testing of Chemicals, Section 1 – Physical-Chemical Properties, OECD 111, Council Regulation (EC) No 440/2008, Guideline Part C – Methods for the Determination of Ecotoxicity, C.7. “Abiotic Degradation: Hydrolysis as a Function of pH”.

As the test item was expected to undergo fast hydrolysis in aqueous media the hydrolysis behaviour was investigated at 20 °C in demineralized water up to a degradation of >90 %. The stability was monitored by HPLC analysis with MS/MS-detection.

The concentration of the substance in the hydrolysis test solutions was determined by HPLC-MS/MS at defined time intervals after derivatization of the NCO function with dibutylamine.

Analytical result:

For the test item abiotic degradation >90 % was observed within 120 min at 20 °C in demineralized water.

Overall hydrolysis at 20 °C

2-ethylhexyl N-(6-isocyanatohexyl)carbamate first determination				2-ethylhexyl N-(6-isocyanatohexyl)carbamate second determination
Hydrolysis time	pH-value	Conc.	Recovery of the initial concentration	Hydrolysis time	pH-value	Conc.	Recovery of the initial concentration
		[µg/L]	[%]			[µg/L]	[%]
0 min	6.4	67.44	100.0	0 min	7.3	62.20	100.0
15 min	6.6	43.34	64.3	15 min	6.7	43.92	70.6
29 min	6.8	27.20	40.3	30 min	6.8	27.26	43.8
60 min	7.3	13.05	19.3	60 min	5.6	10.80	17.4
120 min	7.4	2.81	4.2	120 min	7.6	1.15	1.9
Half life time at 20 °C	t1/2= 0.44 hours			Half life time at 20 °C	t1/2= 0.34 hours
Hydrolysis rate constant	k = 4.36 x 10^-4s^-1			Hydrolysis rate constant	k = 5.60 x 10^-4s^-1

Remark: pH-values could not be determined precisely with the pH meter due to lack of ions in the hydrolysis test solutions

The concentration of the test item after 120 min is determined to be <5 % of the initial value.

The test item is therefore considered to be hydrolytically unstable in demineralized water at 20 °C.

According to OECD 111 Guideline a sterility test was conducted at the end of >90 % hydrolysis. No microbes (colonies) were found. Therefore biotic degradation can be excluded.

The following half-life time and hydrolysis rate were calculated for 20 °C:

Half-life time: 0.4 hours (mean of two determinations)

Hydrolysis rate constant: k = 4.98 x 10^-4s^-1 (mean of two determinations)

Key value for chemical safety assessment

Half-life for hydrolysis:

0.4 h

at the temperature of:

20 °C

Additional information

Due to the observed rapid degradation of the test item within minutes, an exact determination of half-life time or hydrolysis rate was not possible. Therefore the calculated halt-life times of the substance are estimated values related to the initial value at 0 min, which was set to 100 %.

Due to the poor water solubility of the test item, a test concentration of 100 μg/L (including 1 % acetonitrile as organic solvent additive) had to be applied for adequate dissolution. The low substance concentration in the hydrolysis test solutions did not allow the identification of hydrolysis products with the applied analytical method which has to be used to follow the degradation of the parent substance. Polymeric or oligomeric ureas as potential hydrolysis products of the substance could not be determined as they are assumed to be insoluble in water.