Triphenyl phosphate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: study in accordance with generally accepted scientific principles and described in sufficient detail (also assessed by OECD)

Qualifier:

no guideline followed

Principles of method if other than guideline:

Hydrolysis carried out at various pHs and analysis carried out for TPP after extraction with methylene chloride

GLP compliance:

not specified

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Aliquots of the aqueous solutions were extracted with methylene chloride

Buffers:

pH 5 (0.05M) - potassium acid phthalate/sodium hydroxide
pH 7 (0.05M) - potassium orthophosphate/sodium orthophosphate
pH 9 (0.05M) - boric acid/sodium hydroxide

Details on test conditions:

Buffers and glassware were sterilised by autoclaving before use. The phosphate esters were added as concentrated methanol solutions to give an initial concentration of 50µg/litre.

Positive controls:

no

Negative controls:

no

Transformation products:

not measured

pH:

5

Temp.:

25 °C

DT50:

> 28 d

pH:

7

Temp.:

25 °C

DT50:

19 d

pH:

9

Temp.:

25 °C

DT50:

3 d

Validity criteria fulfilled:

not specified

Conclusions:

More rapid hydrolysis under alkaline conditions compared to acidic conditions

Executive summary:

Hydrolysis is more rapid under alkaline conditions (pH 9) with a half-life of 3 days compared to lower pH values where the half-life was 19 days at pH 7 and >28 days at pH 5 all conducted at a temperature of 25 °C.

Description of key information

The key study gave half lives of 3 days at pH 9, 19 days at pH 7 and >28 days at pH 5 at 25 °C.

Key value for chemical safety assessment

Half-life for hydrolysis:

28 d

at the temperature of:

25 °C

Additional information

Several Studies have been performed at various pHs - all studies indicate rapid hydrolysis under alkaline conditions.

One study indicated that 100 % of the TPP had hydrolysed after 10 minutes at pH 13, whilst at pH 4 the rate of disappearance was too slow to measure. All studies show that under alkaline conditions TPP is rapidly degraded, whilst under acidic conditions TPP is relatively stable.

Reported hydrolysis products were diphenyl phosphate and phenol. Further hydrolysis of diphenyl phosphate was considered much slower as monophenyl phosphate was not found in these experiments, and diphenyl phosphate was considered stable under alkaline conditions with reference to an older paper.