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Physical & Chemical properties

Water solubility

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Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
07 October 2019 - 20 March 2020
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Mean recovery (147%) and coefficient of variation (27%) of accuracy samples at low concentration level (0.2µg/L) did not meet validity criteria (70-110% and ≤ 20%, respectively). Mean recovery of accuracy samples at the high concentration level (1000µg/L) was 69%, thus slightly lower than the criteria range (70-110%). However, it was stated that this was due to the SPE treatment of aqueous samples and it was therefore appropriate to use a mean value from all analyses as the water solubility value.
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Version / remarks:
04 March 2016
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Version / remarks:
27 July 1995
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7840 (Water Solubility)
Version / remarks:
March 1998
Qualifier:
according to guideline
Guideline:
other: Method validation conducted based on EC SANCO/3029/99 rev. 4.
Version / remarks:
Revision 4: Guidance for Generating and Reporting Methods of Analysis in Support of Pre-Registration Data Requirements for Annex II (Part A, Section 4) and Annex III (Part A, Section 5) of Directive 91/313.11/07/00
GLP compliance:
yes
Other quality assurance:
other: This study report was inspected by the test facility quality assurance unit according to the standard operating procedures.
Type of method:
flask method
Water solubility:
0 g/L
Conc. based on:
test mat. (dissolved fraction)
Loading of aqueous phase:
10 other: µL/L
Incubation duration:
72 h
Temp.:
20 °C
pH:
6.7
Remarks on result:
other: Estimated value calculated from mean of all analysed concentrations taken in duplicate at 24, 48 and 72h. Analysed concentrations were estimated by extrapolation of the calibration curve.
Details on results:
Preliminary test: Content of the test item dissolved in the water sample was 8.0 E-8 g/L
Main study: A high spread of results was observed in method validation. Therefore, it was decided to report the water solubility of the test item as an estimated value of the mean of all analyzed concentrations. A significant response at the retention tie of the test item was detected in the chromatogram of the pretreated sample from the blank water mixture. Therefore, it was decided to repeat the determination of the blank. In the repeated test, no test item was detected in the pretreated sample from the blank water mixture.

The study did not meet the validity critera for mean recovery (70-110%) and coefficient of variation (≤20%) of accuracy samples in the lowest concentration level (0.2µg/L) which were 147% and 27% respectively. Also, mean recovery of accuracy samples at the highest concentration level (1000µg/L) was 69%, which was slightly outside of the valid range. However, it was stated that this was due to the SPE treatment of aqueous samples and the water solubility value (calculated as a mean of all solubility values in the test) is reliable.

Table 1. Water solubility of TNPS

Stirring time

[hours]

Analyzed concentration1
[g/L]

Mean2

[g/L]

pH

24

6.0 x 10-8

6.3 x 10-8

6.7

5.0 x 10-8

48

3.9 x 10-8

6.7

4.2 x 10-8

72

1.36 x 10-7

6.7

5.1 x 10-8

1 - Estimated value, calculated by extrapolation of the calibration curve

2 - Estimated value.

Method validation attempt 1:

Specificity: A small response at the retention time of the test item was detected in the chromatogram of the blank QC sample. The contribution of the response to the LOQ level was 0.83%. Since this value was < 30%, the specificity requirements were met and the analytical method was found to be specific for the test item.

Calibration curve: The calibration curve was constructed using all data points. There was a linear relationship between response and test item concentration in the range of 0.0400 – 30.0 µg/L (in end solution). Since the coefficient of correlation (r) was > 0.99 and the back calculated accuracies of the remaining data points were in the range 85-115% the calibration line was accepted.

Accuracy and repeatability: The mean accuracy at low concentration levelwas did not met the criteria of 70-110% and coefficient of variation of≤20% (Table 2).

Table 2 - Repeatability of method validation attempt 1

Concentration
[µg/L]

Accuracy
[%]

Coefficient of variation
[%]

Target

Nominal

Analyzed

Individual

Mean

0.1

0.100

0.0431

43

69

35

 

0.100

0.0531

53

 

 

 

0.100

0.0872

87

 

 

 

0.100

0.100

100

 

 

 

0.100

0.0591

59

 

 

1000

1000

841

84

86

3.4

 

1000

823

82

 

 

 

1000

850

85

 

 

 

1000

899

90

 

 

 

1000

871

87

 

 

Stability of analytical system and end solutions: Since the coefficient of variation only at high concentration level was ≤ 20% the analytical system and end solutions were not stable over at least a 5.45 hour time interval.

Stability of stock solutions: The coefficient of variation on the response factors of the calibration solutions prepared with fresh and stored stock solutions was 5.8%. Since the value was ≤ 10% the stock solutions were stable when stored at room temperature for at least 7 days.

Storage stability of samples: The test item was stored in afreezer(≤ -15°C). The mean accuracy of the frozen QC samples fell in the criterion 70-110%, but results could not be accepted because the analytical system was not stable.

Conclusion: Because the analytical system was not stable during method validation, the validation was repeated. During method validation attempt II, the responses were too low during this validation and therefore no calculations were performed. It was decided to continue with method development to achieve a more robust method.

 

The study report did not present the findings from method validation attempt 2

 

Method validation attempt 3:

Specificity: The chromatogram of the blank QC sample showed no peak at the retention time of the test item. Since no interferences were detected, the specificity requirements were met and the analytical method was found to be specific for the test item.

 

Calibration curve: The calibration curve was constructed using all data points. There was a linear relationship between response and test item concentration in the range of 0.700 – 10.0 µg/L (in end solution). Since the coefficient of correlation (r) was > 0.99 and the back calculated accuracies of the remaining data points were in the range 85-115% the calibration line was accepted.

Accuracy and repeatability: The mean accuracy at low concentration leveldid not met the criteria of 70-110% and coefficient of variation was >20% at both concentration levels (Table 3).

Table 3 - Repeatability of method validation attempt 3

Concentration
[µg/L]

Accuracy
[%]

Coefficient of variation
[%]

Target

Nominal

Analyzed

Individual

Mean

0.1

0.100

0.0521

52

59

31

 

0.100

0.0461

46

 

 

 

0.100

0.0441

44

 

 

 

0.100

0.0661

66

 

 

 

0.100

0.0888

89

 

 

1000

1000

1057

106

102

20

 

1000

1352

135

 

 

 

1000

847

85

 

 

 

1000

881

88

 

 

 

1000

957

96

 

 

 

Stability of analytical system and end solutions: Since the coefficient of variation at both concentration levels was ≤ 20% the analytical system and end solutions were stable over at least a 1.33 hour time interval.

Stability of stock solutions: The coefficient of variation on the response factors of the calibration solutions prepared with fresh and stored stock solutions was 9.8%. Since the value was ≤ 10% the stock solutions were stable when stored at room temperature for at least 41 days.

Conclusion: Because the accuracy and repeatability did not meet the criteria, it was decided to repeat method validation with LOQ level of 0.2 µg/L thus with concentration factor of five. Due to the pronounced adsorption of the test item to the tubing needed to apply water sample to the SPE column higher volume of dichloromethane needs to be used during the elution step to make sure that all the test item is eluted.

 

Final method validation:

Specificity: The chromatogram of the QC sample showed one major test item peak. The area of this peak was used as response in the calculations. A significant response at the retention time of the test item was detected in the chromatogram of the blank QC sample. The contribution of the response to the LOQ level was 58%. Also, the mean accuracy at low concentration levelwas very high (i.e. 948%). Therefore, determination of accuracy and repeatability at low concentration level and specificity was repeated. The chromatogram of the blank QC sample showed no peak at the retention time of the test item. Since no interferences were detected, the specificity requirements were met and the analytical method was found to be specific for the test item.

Calibration curve: The calibration curve was constructed excluding one data point since the back calculated accuracy was > 15% from the nominal concentration. There was a linear relationship between response and test item concentration in the range of 0.600 – 10.0 µg/L (in end solution). Since the coefficient of correlation (r) was > 0.99 and the back calculated accuracies of the remaining data points were in the range 85-115% the calibration line was accepted.An additional calibration curve was prepared and analyzed to perform the repeated accuracy and repeatability testand storage stability of samples. Two data points were excludedsince the back calculated accuracy was > 15% from the nominal concentration. The resulting curve was similar to the validation curve and fell within the criteria ranges.

Accuracy and repeatability: The mean accuracy at low concentration levelwas very high (i.e. 948%), probably caused by contamination because the blank contained also a large amount of test item (Table 4). Therefore, determination of accuracy and repeatability at low concentration level was repeated. The SPE treatment of aqueous samples resulted in a method with high spread in results at the low concentration level of 0.2 µg/L. Mean recovery and coefficient of variation of accuracy samples at low concentration level (0.2 µg/L) did not meet validation criteria (respectively 70-110% and ≤20%). Mean recovery was 147% and coefficient of variation was 27%. Mean recovery of accuracy samples at high concentration level (1000 µg/L) was 69%, that is slightly below the criteria (70-110%). Considering the multiple method development and validation attempts method was accepted for the analysis of the test item in water in the target concentration range of 0.2 - 1000 µg/L as the best possible method for quantification of test item in water samples. Due to the high spread, it is advised to take duplicate samples for aqueous samples containing the test item. Samples of M2-medium will not be supported with this method. Stock solutions from the eco toxicological studies can be analysed by dilution in dichloromethane on a dichloromethane calibration curve, no SPE treatment is necessary.Additional QC samples in M2-medium were analyzed.The mean accuracies were in the range of 70‑110%, but below (low level) or above (high level) the concentrations in water. Therefore, the analytical method was accepted for the support of ecotoxicological when matrix matched curves were used.

Table 4 - Repeatability of the final method validation

Concentration
[µg/L]

Accuracy
[%]

Coefficient of variation
[%]

Target

Nominal

Analyzed

Individual

Mean

0.2

0.200

1.52

760

948

49

 

0.200

1.86

931

 

 

 

0.200

3.42

1718

 

 

 

0.200

1.72

859

 

 

 

0.200

0.940

470

 

 

0.21

0.200

0.317

159

147

27

 

0.200

0.258

129

 

 

 

0.200

0.393

197

 

 

 

0.200

0.321

160

 

 

 

0.200

0.181

91

 

 

1000

1000

778

78

69

8.3

 

1000

699

70

 

 

 

1000

625

62

 

 

 

1000

696

70

 

 

 

1000

660

66

 

 

 

Limit of quantification:The limit of quantification (LOQ) was assessed at 0.2 µg/L in water.

Stability of the analytical system and end solutions: Since the coefficient of variation at all concentration levels was ≤ 20% the analytical system and end solutions were stable over at least a 1.37 hour time interval.Additional data on the stability of the analytical system and end solutions was obtained with the analysis of the repeated accuracy and repeatability test and storage stability of samples. The results were similar to the validation results and fell within the criteria range.

 

Stability of stock solutions: The coefficient of variation on the response factors of the calibration solutions prepared with fresh and stored stock solutions was 8.0%. Since the value was ≤ 10% the stock solutions were stable when stored at room temperature for at least 21 days.

 

Storage stability of samples: Samples of the test item were stored in the freezer(≤ -15°C). Since the mean accuracy of the frozen QC samples did not fell in the criterion 70-110% the samples were not stable when stored in the freezer(≤ -15°C).

 

Conclusions:
A water solubility of 6.3E-8 g/L at 20 C and pH 6.7 was determined for the submission substance Di-tert-Nonyl Polysulfide (TNPS 537) using a slow-stirring flask method. Quantitative chemical analysis was performed using UPLC-MS. The study did not meet the validity criteria for mean recovery (70-110%) and coefficient of variation (≤20%) of accuracy samples in the lowest concentration level (0.2µg/L) which were 147% and 27% respectively.

Also, mean recovery of accuracy samples at the highest concentration level (1000µg/L) was 69%, which was slightly outside of the valid range. However, it was stated that this was due to the SPE treatment of aqueous samples and therefore, for the purposes of stating that the test substance has an extremely low solubility, the results are considered reliable.
Endpoint:
water solubility
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
01/03/07 to 20/10/08
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non GLP, guideline study.
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
not specified
GLP compliance:
no
Type of method:
column elution method
Water solubility:
< 0.154 mg/L
Temp.:
20 °C
pH:
7
Details on results:
Standard temperature and pH assumed.

Detection limit = 0.154 mg/L.

Conclusions:
The water solubility of polysulfide di-tert-nonyl of <0.154 mg/L has been read across from polysulfide di-tert-dodecyl.
Executive summary:

The water solubility of polysulfide di-tert-nonyl has been read across from polysulfide di-tert-dodecyl. Gancet (2008) is a column elution method study following OECD guideline 105. This study is considered reliable and suitable for use for this endpoint.

Description of key information

The water solubility of the registration substance at 20°C and pH 6.7 was 6.3E-8 g/L (i.e. 0.063 µg/l).

Key value for chemical safety assessment

Water solubility:
0.063 µg/L
at the temperature of:
20 °C

Additional information

A water solubility of 6.3E-8 g/L at 20 degrees C and pH 6.7 was determined for the submission substance Di-tert-Nonyl Polysulfide (CAS 68425-16-1, EC 270-336-2) using a slow-stirring flask method. Quantitative chemical analysis was performed using UPLC-MS. The study did not meet the validity critera for mean recovery (70-110%) and coefficient of variation (≤20%) of accuracy samples in the lowest concentration level (0.2µg/L) which were 147% and 27% respectively. Also, mean recovery of accuracy samples at the highest concentration level (1000µg/L) was 69%, which was slightly outside of the valid range. However, it was stated that this was due to the SPE treatment of aqueous samples and the water solubility value (calculated as a mean of all solubility values in the test) is reliable for this endpoint and demonstrates the very low solubility of the registration substance.

The slow-stirring flask method was also applied for the determination of the water solubility of the analogue substance polysulfides, di-tert-dodecyl. Analysis of the test item was made according to an UPLC-MS/MS specific method making use of derivatization with AgBF4. The water solubility of the test item at 20°C was found to be 2.60 x 10-7 g/l (i.e. 0.260 µg/l). The pH of the aqueous samples was 7.3.