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Environmental fate & pathways

Hydrolysis

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Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Experimental phase: 23 February 2011 to 21 April 2011. Report issued 12 July 2011.
Reliability:
1 (reliable without restriction)
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The read-across is based on the hypothesis that the Source and Target substances will have similar toxicological and ecotoxicological properties, due to their extremely close physico-chemical properties and structural similarities. For example, both the Source and Target substances are mono-constituents which share structural similarities and contain the same functional groups.
The Source substance has a comprehensive data set generated for a REACH Annex VII registration and this along with its similarity to the Target substance are considered sufficient to consider the read-across an appropriate adaptation to the standard information requirements of Annex VII of the REACH regulation for the Target substance in accordance with the provisions of Annex XI, 1.5 of the REACH regulation.
The Source substance and the Target substance are structurally identical the difference lies in the salt form i.e. the counter ion. In the case of the Source substance the counter ion is a potassium ion whereas in the Target substance the counter ion is a hydrogen .



Both the Source and Target substances have similar molecular weights of 1073 and 921 respectively. The difference in molecular weight is due to the counter ions. The Source substance is the potassium salt of the Target substance.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

The Source and Target substance have similar purity profiles. Water is the main impurity in both substances. Both substances contain impurities that are analogues of the Source molecule. Neither substance contains purposely added diluents or additives.
The Source and Target are manufactured using the same chemical synthetic route. The difference in salt form is the difference between the two substances.

3. ANALOGUE APPROACH JUSTIFICATION
The Target substance is the free acid salt of the Source substance, hence the Target contains all the same functional groups as the Source substance. It is anticipated that the physicochemical results of the Target and the Source substance will be very similar.
It is expected that the water solubility of the Target Substance will be slightly lower than the Source substance, although environmental conditions will impact on the degree of solubility. Even though the water solubility values are differ , both the Source and Target substance are extremely water soluble and neither will have a tendency to partition into lipids or body fats. The potential for systemic absorption is considered to be low for both substances as their bioavailability is expected to be low due to the high molecular weights of the molecules and low lipophilicity, which precludes easy passage across biological membranes.
For the full read across assessment dossier see the attached Read-across assessment framework report


4. DATA MATRIX
See Read-Across Assessment Framework Report

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2011
Report Date:
2011

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Study design

Analytical monitoring:
yes
Buffers:
Preparation of Buffer Solutions
pH 4.0 Buffer Solution
164ml of 0.2M acetic acid solution was added to 36ml of 0.2M sodium acetate and diluted to
1 litre with distilled / deionised water. The solution was degassed with helium.

pH 7.0 Buffer Solution
296ml of 0.1M sodium hydroxide solution was added to 500ml of 0.1M monopotassium
phosphate solution and diluted to 1 litre with distilled / deionised water. The solution was
degassed with helium.

pH 9.0 Buffer Solution
213ml of 0.1M sodium hydroxide solution was added to 500ml of 0.1M boric acid in 0.1M
potassium chloride and diluted to 1 litre with distilled / deionised water. The solution was
degassed with helium.
The pH of each buffer solution was measured prior to use.
Details on test conditions:
Preparation of Test Solutions
The tests were prepared in duplicate and the pH of each stable solution was measured prior
to storage at 50 ±1ºC. Analysis of the tests (by HPLC), was carried out initially and at
intervals over 5 days. Samples were weighed into 50ml volumetric flasks and buffer was
added
Duration of testopen allclose all
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
6.44 g/L
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
5.936 g/L
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
6.089 g/L
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
6.54 g/L
Number of replicates:
2
Positive controls:
no
Negative controls:
no
Statistical methods:
None

Results and discussion

Preliminary study:
At pH 7 and 9 there was less than 10% hydrolysis after 5 days at 50ºC. The substance was not soluble at pH 4. The test substance is considered to be hydrolytically stable.
Transformation products:
not measured
Total recovery of test substance (in %)open allclose all
% Recovery:
100.3
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
100.9
pH:
9
Temp.:
50 °C
Duration:
5 d
% Recovery:
103.1
pH:
9
Temp.:
50 °C
Duration:
5 d
Dissipation half-life of parent compoundopen allclose all
Key result
pH:
7
Temp.:
25 °C
Half-life:
> 1 yr
Key result
pH:
9
Temp.:
25 °C
Half-life:
> 1 yr

Any other information on results incl. tables

 Test  Concentration g/L  Initial result g/L  Result after 5 days g/L  Recovery after 5 days %  % loss
 pH7 (1)  6.342  6.440  6.457  100.3  -0.3
 pH7 (2)  5.854  5.936  5.953  100.3  -0.3
 pH9 (1)  6.008  6.089  6.141  100.9  -0.9
 pH9 (2)  6.476  6.540  6.742  103.1  -3.1

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
At pH 7 and 9 there was less than 10% hydrolysis after 5 days at 50ºC. The substance was not soluble at pH 4.
Executive summary:

Introduction

Hydrolysis as a function of pH was determined for the test item using a method designed to be compliant with Method C7-preliminary test

Method

Hydrolysis was intended to be measured at pH 4.0, pH 7.0 and pH 9.0 using a preliminary test. The test substance was not soluble at pH 4.0 and therefore hydrolysis was not assessed at this pH. As no significant hydroysis was observed in the preliminary test further testing was not required.

 Results and Conclusion

At pH 7 and 9 there was less than 10% hydrolysis after 5 days at 50ºC. The substance was not soluble at pH 4.