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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
6-27 March 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
In-house study. PFW Aroma Chemicals has a long history of monitoring AHTN in waste water of various pH that needs to be submitted to the local authorities for the purpose of maintaining the license to produce. A validated protocol has been developed and laboratory staff has been trained and is very experienced.
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
Tier 1
Deviations:
yes
Remarks:
see method
Principles of method if other than guideline:
A water sample was spiked with AHTN and the temperature of the sample is maintained at 50 ± 0.5°C for a period of 5 days. The AHTN content has been analysed once the Tonalid has been dissolved completely and 5 days later by Gas Chromatography.
GLP compliance:
no
Radiolabelling:
no
Analytical monitoring:
not required
Duration:
5 d
pH:
4
Initial conc. measured:
495 µg/L
Duration:
5 d
pH:
7
Initial conc. measured:
257 µg/L
Duration:
5 d
pH:
9
Initial conc. measured:
>= 497 - <= 512 µg/L
Transformation products:
no
% Recovery:
ca. 99
pH:
4
Temp.:
50 °C
Duration:
5 d
% Recovery:
> 99
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
>= 94 - <= 96
pH:
9
Temp.:
50 °C
Duration:
5 d
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
0 d-1
Type:
not specified
pH:
7
Temp.:
50 °C
Hydrolysis rate constant:
0 d-1
Type:
not specified
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
0 d-1
Type:
not specified

pH4

The area counts of the peaks in the chromatogram for both the Tonalid and the 12 -OHD are all similar for the duplo measurements, indicating no major changes in test system due to loss of material. The Tonalid:Phantolid ratio has also been calculated as an additional check in the verification of the results. It seems that the ratio based on the measurements remained fixed at 0.84. The pH remained stable during the test.

pH=7

No Phantolid was used in the test since the stability of 12-OHD in water has been checked. The theoretical concentration of Tonalid in water was 259μg/l. The average initial measured concentration was 257μg/l, which is a recovery of >99%. The concentration after 5 days was 242μg/l corresponding to 94% of the initial measured concentration. The pH remained stable during the test.

pH=9

Measured concentrations could not be determined on the basis of the internal standard 12-OHD. Tonalid: Phantolid ratios remained stable, but the 12-OHD peak disappeared during the test. Hence, the ratio Tonalid:Phantolid has been used. The Tonalid: Phantolid ratios based on measurements are similar to the ratios for the sample at pH=4. The counts in the Chromatogram are also similar. Therefore, Phantolid can also be used as an internal standard. Even when taking the Phantolid initial recovery of 97% at pH=4 into account, the initial recovery is 94-96%. The pH remained stable during the test. The final recovery is based on the measured counts of the Tonalid and Phantolid peaks.

Validity criteria fulfilled:
yes
Remarks:
See overall remarks.
Conclusions:
Less than 10 % of hydrolysis is observed after 5 days, therefore Tonalid (AHTN) is considered hydrolytically stable. No additional testing or a higher tier assessment on hydrolysis is required.
Executive summary:

Water samples were spiked with AHTN and each sample was stirred for 24 hours to ensure proper dissolution. The pH of the solution was set to 4, 7 and 9 with 0.5M NaOH 0.5M HCl in water. The samples were divided into two parts. One part was used to determine the initial concentration, while the other part was stored in a glass bottle at 50 ± 0.5°C for a period of 5 days. After 5 days, AHTN was extracted from the sample with Solid Phase Extraction and anaysed by Gas Chromatography equipped with a Flame Ionisation Detector (FID).

No hydrolysis was observed for all the samples and hence no degradation product could be identified.AHTN remained stable in acidic, neutral and alkaline solution.

Description of key information

A water sample was spiked with the test item and the temperature of the sample is maintained at 50 ± 0.5°C for a period of 5 days at pH 4, 7 and 9, in line with OECD TG 111. The test item content was analysed once the the test item was dissolved completely and 5 days later by Gas Chromatography. As less than 10% disappeared, the half-life time at 25 ºC is considered to be > 1 year.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

Inhouse experience with the test iem suggests that the test item is very stable in acidic and alkaline media. It does not discolour in soaps, toiletries, cold-wave preparations or chlorinated detergents. During the development of the EU risk assessment report of the test item, expert judgement also concluded that it would not hydrolyse based on the absence of chemical groups that could spontaneously degrade in acidic and alkaline aqueous media.

 

It has been demonstrated that the test item is stable in aqueous media at acidic, neutral and alkaline media at elevated temperatures (50°C) for several days. According to the hydrolysis testing guidelines of the Organisation for Economic Co-operation and Development, if less than 10% of hydrolysis is observed (corresponding to a half life time of more than one year), the test substance is considered hydrolytically stable. For the test item, this is clearly the case since no hydrolysis was observed.