Copper, [29H,31H-phthalocyaninato(2-)-N29,N30,N31,N32]-, sulfonated

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

other: Method Development

Adequacy of study:

other information

Study period:

18 October 2017

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

A hydrolysis trial was conducted in order to determine whether a suitable analytical method could be utilised in order to the measure the hydrolysis of the test material in relation to pH.
As the test material is a UVCB, a surrogate ICP methodology was previously developed and implemented for the determination of the solubility of the test material. For the hydrolysis study, the copper surrogate methodology, where all copper containing components are collectively measured as an integrated total copper response, would not have been capable of distinguishing between parent compound and hydrolysis products. Therefore, a hydrolysis trial was conducted using pH measurement and changes in pH as a possible surrogate indicator of hydrolysis, where the generated of protons essentially serves as a potential measure of possible parent degradation.

Solutions of the test material was prepared in pH 5, 7 and 9 buffers at concentration of 1.8, 1.8 and 2.0 mg/L, respectively. A light was shone through each solution during the test period (six days) to observe Tyndall effect in the solutions. This was also repeated after sonicating aliquots for 20 minutes. Aliquots were also centrifuged at very high speed.
An aliquot of each solutions was taken for initial (Day 0) pH measurement. Portions of each solution were decanted to glass vials, filling each to minimise headspace. The vessels were then sealed. The vials were placed in darkness in an incubator set to 50 °C. At each sampling interval (Day 1, 2, 3 and 6) a vial at each pH was removed from the incubator, allowed to cool to room temperature and the pH measured.

GLP compliance:

not specified

Radiolabelling:

not specified

Analytical monitoring:

no

Details on sampling:

- Sampling intervals/times for pH measurements: Days 1, 2, 3 and 6
- Other observation, if any (e.g.: precipitation, color change etc.): Tydall effect observations were made throughout the study

Buffers:

- pH: 4, 7 and 9

Details on results:

Tyndall effect was evident when shining a light through each solution at test initiation. This effect was noted after day 6 and after sonicating aliquots for 20 minutes. Tyndall effect was only eliminated after high speed centrifugation (23000 x g for 20 minutes). The hydrolysis trial test concentrations were deemed appropriate for this test material in buffers based on the solubility data in reagent water. It was expected that reducing the concentrations would have mitigated measurement of potential pH changes caused by hydrolysis.
The measured pH values do not show any apparent pattern or trend. Based on these results, pH was deemed not to be a suitable indicator of hydrolytic degradation.

Table 1: Results of pH measurements

Sampling Interval (day)	Measured pH
	pH 5 Buffer Conc. 1.8 mg/L	pH 7 Buffer Conc. 1.8 mg/L	pH 7 Buffer Conc. 1.8 mg/L
0 (initiation)	5.05	7.15	9.12
1	5.09	7.17	9.07
2	5.08	7.16	9.06
3	5.05	7.18	9.08
6	5.07	7.19	9.10

Validity criteria fulfilled:

no

Conclusions:

Several hydrolytic degradation methods were developed, copper surrogate and pH, but neither method was a suitable indicator of hydrolytic degradation of the test substance.

Executive summary:

A hydrolysis trail was conducted to investigate the feasibility of using pH measurement to assess hydrolytic degradation of the test substance. Due to the complex nature of the UVCB substance, a copper surrogate ICP methodology was previously developed and implemented for the determination of the solubility of the test item. However, for a hydrolysis study this copper surrogate methodology, where all copper containing components were collectively measured as an integrated total copper response, would not be capable of distinguishing between parent compound and components and hydrolytic degradation products. Therefore, it was determine that pH measurement and changes in pH was a possible potential measure of possible parent degradation. Several pH values were used during sampling days 1, 2, 3, and 6. The pH values did not show any apparent patterns or trends. Based on these values, pH was deemed not a suitable indicator of hydrolytic degradation of the test substance.

Description of key information

A hydrolysis trail was conducted to investigate the feasibility of using pH measurement to assess hydrolytic degradation of the test substance. Due to the complex nature of the UVCB substance, a copper surrogate ICP methodology was previously developed and implemented for the determination of the solubility of the test item. However, for a hydrolysis study this copper surrogate methodology, where all copper containing components were collectively measured as an integrated total copper response, would not be capable of distinguishing between parent compound and components and hydrolytic degradation products. Therefore, it was determine that pH measurement and changes in pH was a possible potential measure of possible parent degradation. Several pH values were used during sampling days 1, 2, 3, and 6. The pH values did not show any apparent patterns or trends. Based on these values, pH was deemed not a suitable indicator of hydrolytic degradation of the test substance.