Registration Dossier

Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Testing was conducted between 23 December 2009 and 03 March 2010.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

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 (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Radiolabelling:
no

Study design

Analytical monitoring:
yes
Details on sampling:
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 0.500 g/l in the three buffer solutions. A 1% co-solvent of acetonitrile was used to aid solubility.

The test solutions were split into individual vessels for each data point.

The solutions were shielded from light whilst maintained at the test temperature.

Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5°C for a period of 120 hours.
Buffers:
Buffer Solution (pH 4)
Components: Potassium hydrogen phthalte
Concentration (mMol dm-3): 10

Buffer Solution (pH 7)
Components: Disodium hydrogen orthophosphate (anhydrous), Potassium dihydrogen orthophosphate, Sodium chloride
Concentration (mMol dm-3): 6, 4 and 4 respectively

Buffer Solution (pH 9)
Components: Disodium tetraborate, Sodium chloride
Concentration (mMol dm-3): 2 and 4 respectively

The buffer solutions were filtered through a 0.2 µm membrane filter to ensure they were sterile before commencement of the test. Also these solutions were subjected to ultrasonication and degassing with nitrogen to minimise dissolved oxygen content.
Details on test conditions:
Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5°C for a period of 120 hours.
Duration of testopen allclose all
Duration:
120 h
pH:
4
Initial conc. measured:
0.169 g/L
Duration:
120
pH:
7
Initial conc. measured:
0.168 g/L
Duration:
120
pH:
9
Initial conc. measured:
0.189 g/L
Number of replicates:
Duplicate aliquots (A and B) of sample solution were diluted by a factor of 5 using methanol at each timepoint.
Positive controls:
no
Negative controls:
no

Results and discussion

Preliminary study:
All pH's: Apparent hydrolysis attributed to a cumulative reduction in the concentration of a number of less significant dissolved components present, the quantification of which was beyond the scope of the method guideline. Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C when considering the isopropyl ether content only/specifically.
Test performance:
Equivalent test material concentrations based on the isopropyl ether peak areas only were also determined at each timepoint as this component was identified as the dominant soluble component at lower, more environmentally relevant concentrations.
Transformation products:
not specified
Dissipation DT50 of parent compoundopen allclose all
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Type:
other:
Remarks on result:
other: Conclusion based on the isopropyl ether content of the test material.
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Type:
other:
Remarks on result:
other: Conclusion based on the isopropyl ether content of the test material.
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Type:
other:
Remarks on result:
other: Conclusion based on the isopropyl ether content of the test material.
Details on results:
At pH4, 7 and 9 there was less than 10% hydrolysis after 120 hours at 50°C when monitoring the isopropyl ether content of the test material, equivalent to a half-life greater than 1 year at 25°C.

Any other information on results incl. tables

The mean total peak areas and the mean isopropyl ether peak areas relating to the standard and sample solutions are shown in the following table:

Solution

Mean Total Peak Area

Mean Isopropyl Ether Peak Area

Standard 100 mg/l

1.474 x 103

584.320

Standard 105 mg/l

1.537 x 103

620.122

pH 4 Matrix Blank

68.193

50.920

Initial Sample A, pH 4

503.524

284.340

Initial Sample B, pH 4

492.150

279.594

Standard 103 mg/l

1.472 x 103

596.057

Standard 112 mg/l

1.630 x 103

649.095

pH 4 Matrix Blank

84.645

52.027

24 Hour Sample A, pH 4

525.636

289.728

24 Hour Sample B, pH 4

556.744

317.130

Standard 114 mg/l

2.222 x 103[1]

675.269

Standard 103 mg/l

1.538 x 103

616.006

pH 4 Matrix Blank

98.537

57.451

48 Hour Sample A, pH 4

513.625

286.438

48 Hour Sample B, pH 4

501.418

286.584

Standard 131 mg/l

2.112 x 103

865.974

Standard 112 mg/l

1.785 x 103

735.324

pH 4 Matrix Blank

90.576

57.865

120 Hour Sample A, pH 4

487.010

302.295

120 Hour Sample B, pH 4

474.933

300.682

Standard 100 mg/l

1.502 x 103

600.682

Standard 105 mg/l

1.536 x 103

621.155

pH 7 Matrix Blank

89.080

35.596

Initial Sample A, pH 7

491.139

281.784

Initial Sample B, pH 7

500.157

287.075

 

Continued

Solution

Area

Area

Standard 103 mg/l

1.499 x 103

598.852

Standard 112 mg/l

1.615 x 103

644.665

pH 7 Matrix Blank

113.049

40.548

24 Hour Sample A, pH 7

485.461

267.149

24 Hour Sample B, pH 7

488.150

267.199

Standard 114 mg/l

1.740 x 103

681.418

Standard 103 mg/l

1.502 x 103

605.732

pH 7 Matrix Blank

117.266

42.351

48 Hour Sample A, pH 7

470.307

259.845

48 Hour Sample B, pH 7

471.027

263.348

Standard 131 mg/l

2.161 x 103

902.908

Standard 112 mg/l

1.739 x 103

741.967

pH 7 Matrix Blank

112.761

41.781

120 Hour Sample A, pH 7

448.903

308.943

120 Hour Sample B, pH 7

442.877

308.642

Standard 100 mg/l

1.499 x 103

593.891

Standard 105 mg/l

1.587 x 103

600.655

pH 9 Matrix Blank

106.432

28.662

Initial Sample A, pH 9

564.083

336.907

Initial Sample B, pH 9

571.878

344.326

Standard 103 mg/l

1.535 x 103

611.721

Standard 112 mg/l

1.617 x 103

648.048

pH 9 Matrix Blank

115.773

32.058

24 Hour Sample A, pH 9

511.531

294.623

24 Hour Sample B, pH 9

537.620

316.402

Standard 114 mg/l

1.688 x 103

667.474

Standard 103 mg/l

1.487 x 103

600.004

pH 9 Matrix Blank

129.055

34.065

48 Hour Sample A, pH 9

472.903

280.380

48 Hour Sample B, pH 9

474.622

284.704

Standard 131 mg/l

2.134 x 103

887.767

Standard 112 mg/l

1.787 x 103

753.387

pH 9 Matrix Blank

117.111

35.649

120 Hour Sample A, pH 9

490.241

344.995

120 Hour Sample B, pH 9

515.736

359.867

 


The equivalent test material concentrations based on the total peak areas at the given time points are shown in the following tables:

pH 4 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

Concentration (g/l)

0.171

0.167

0.182

0.193

% of mean initial concentration

101

98.9

108

114

pH 4 at 50.0 ± 0.5ºC continued

 

Time (Hours)

48 (A)

 48 (B)

120 (A)

120 (B)

Concentration (g/l)

0.172

0.168

0.152

0.148

% of mean initial concentration

101

98.9

89.7

87.5

Result: Apparent hydrolysis attributed to a cumulative reduction in the concentration of a number of less significant dissolved components present, the quantification of which was beyond the scope of the method guideline.

pH 7 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

Concentration (g/l)

0.166

0.169

0.168

0.169

% of mean initial concentration

99.1

101

100

101

 pH 7 at 50.0 ± 0.5ºC continued 

 

Time (Hours)

48 (A)

 48 (B)

120 (A)

120 (B)

Concentration (g/l)

0.157

0.158

0.140

0.138

% of mean initial concentration

94.2

94.4

83.9

82.8

Result: Apparent hydrolysis attributed to a cumulative reduction in the concentration of a number of less significant dissolved components present, the quantification of which was beyond the scope of the method guideline.


pH 9 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

Concentration (g/l)

0.187

0.190

0.174

0.183

% of mean initial concentration

99.3

101

92.5

97.2

  pH 9 at 50.0 ± 0.5ºC continued

 

Time (Hours)

48 (A)

 48 (B)

120 (A)

120 (B)

Concentration (g/l)

0.162

0.162

0.152

0.157

% of mean initial concentration

85.7

86.0

80.6

83.2

Result: Apparent hydrolysis attributed to a cumulative reduction in the concentration of a number of less significant dissolved components present, the quantification of which was beyond the scope of the method guideline.

The equivalent test material concentrations based on the isopropyl ether peak areas only at the given time points are shown in the following tables:

pH 4 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

Concentration (g/l)

0.242

0.238

0.250

0.274

% of mean initial concentration

101

99.2

104

114

pH 4 at 50.0 ± 0.5ºC continued

 

Time (Hours)

48 (A)

 48 (B)

120 (A)

120 (B)

Concentration (g/l)

0.240

0.241

0.229

0.228

% of mean initial concentration

100

100

95.7

95.1

Result:         Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.

pH 7 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

Concentration (g/l)

0.236

0.241

0.231

0.231

% of mean initial concentration

99.1

101

96.9

96.9

pH 7 at 50.0 ± 0.5ºC continued

 

Time (Hours)

48 (A)

 48 (B)

120 (A)

120 (B)

Concentration (g/l)

0.219

0.222

0.229

0.228

% of mean initial concentration

91.8

93.0

95.9

95.8

Result:         Less than 10% hydrolysis after 5 days at 50°C, equivalent to a half-life greater than 1 year at 25°C.

pH 9 at 50.0 ± 0.5ºC

 

Time (Hours)

Initial (A)

Initial (B)

24 (A)

24 (B)

Concentration (g/l)

0.282

0.288

0.251

0.270

% of mean initial concentration

98.9

101

88.2

94.7

pH 9 at 50.0 ± 0.5ºC continued

 

Time (Hours)

48 (A)

 48 (B)

120 (A)

120 (B)

Concentration (g/l)

0.240

0.244

0.256

0.267

% of mean initial concentration

84.1

85.4

89.6

93.5

Result:         Less than 10% hydrolysis after 5 days at 50°C, based on mean concentration, equivalent to a half-life greater than 1 year at 25°C.


[1] Excluded from calculations due to suspected contamination/inconsistent peak profile.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The estimated half-life at 25°C of the test material is shown in the following table:

pH Estimated half-life at 25°C
4 >1 year
7 >1 year
9 >1 year

Assessment of hydrolytic stability was based on the isopropyl ether component of the test material only, as this was determined to be the dominate dissolved component in aqueous solutions originating from lower, more environmentally relevant nominal saturation concentrations of 1.0 g/l and 10 g/l during the water solubility testing. In addition the 2-methylpentane component contained no hydrolysable functional groups. When monitoring the sample solutions as equivalent test material concentration using the total peak area of all dissolved components, slightly greater than 10% apparent hydrolysis was observed after 120 hours incubation at 50°C (percentages remaining of 88.6%, 83.3% and 81.9% for pH 4, pH 7 and pH 9 respectively). However, this was concluded to originate from a cumulative reduction in the concentration of a number of less significant dissolved components present, the quantification of which was beyond the scope of the method guideline.
Executive summary:

Assessnt of hydrolytic stability was carried out using Method C7 Abiotic Degradation, Hydrolysis as a Function of pH, Commission Regulation (EC) No 440/2008 of 30 May 2008. The results are as follows:

pH

Estimated half-life at 25°C

4

>1 year

7

>1 year

9

>1 year

--

Assessment of hydrolytic stability was based on the isopropyl ether component of the test material only, as this was determined to be the dominate dissolved component in aqueous solutions originating from lower, more environmentally relevant nominal saturation concentrations of 1.0 g/l and 10 g/l during the water solubility testing. In addition the 2-methylpentane component contained no hydrolysable functional groups. When monitoring the sample solutions as equivalent test material concentration using the total peak area of all dissolved components, slightly greater than 10% apparent hydrolysis was observed after 120 hours incubation at 50°C (percentages remaining of 88.6%, 83.3% and 81.9% for pH 4, pH 7 and pH 9 respectively). However, this was concluded to originate from a cumulative reduction in the concentration of a number of less significant dissolved components present, the quantification of which was beyond the scope of the method guideline.