Calcium bis(metaphosphate)

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Summary report with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Principles of method if other than guideline:

Summary report for three chemical classes about biotic degradation, hydrolysis as a function of pH for phosphates, pyrophosphates and triphosphates.

GLP compliance:

no

Analytical monitoring:

yes

Chemical Class	Substance Used for Experimental Determination	Anticipated Half-Life at 25°C	References
Phosphates Orthophosphates	Not applicable, no possible mechanism for hydrolysis	pH 4 > 1 year pH 7 > 1 year pH 9 > 1 year	N/A
Pyrophosphates Diphosphates	Tetrapotassium Pyrophosphate CAS No. 7320-34-5	pH 4 > 1 year pH 7 > 1 year pH 9 > 1 year	1
Triphosphates Tripolyphosphates	Pentapotassium Triphosphate CAS No. 13845-36-8	pH 4 = 14.5 days pH 7 > 1 year pH 9 > 1 year	2

The hydrolytic half-life anticipated for the anions of specified phosphates, pyrophosphates and triphosphates has been addressed by read across from a single example for each chemical class, where applicable. The ionic substances were assumed to undergo dissociation in aqueous solution and the resulting cation to have negligible influence on the hydrolysis rate of the anion within the buffer solutions used as instructed by Method 111 of the DECD Guidelines for Testing of Chemicals, 13 April

2004.

Such a phenomenon may be replicated at environmentally relevant concentrations and on dissolution into complex environmental matrices. Although the cation composition of the final matrix may retain some minor influence on the hydrolytic rate, such a relationship is considered beyond the scope of the standard test method and would not have been addressed or identified by testing in accordance with OECD Method 111. The reported data was generated using buffer solutions with sodium salt

compositions.

References:

1. Tetrapotassium pyrophosphate: Determination of water solubility and abiotic

degradation, hydrolysis as a function of pH. Harlan Laboratories Ltd, Shardlow, UK, final

report for project number292010047.

2. Pentapotassium triphosphate: Determination of water solubility and abiotic

degradation, hydrolysis as a function of pH. Harlan Laboratories Ltd, Shardlow, UK, final

report for project number292010053.

3. Watanabe, Matsuura and Yamada (1981) The Mechanism of the Hydrolysis of

Polyphosphates. V. The Effect of Cations on the Hydrolysis of Pyro- and Triphophates.

Bull. Chem. Soc. Jpn,54, 738-741.

4. Watanabe (1982) The Mechanism of the Hydrolysis of Polyphosphates. V. The Effect

of Cations on the Hydrolysis of cyclo-Tri- and cyclo-Tetraphosphate.Bull. Chem. Soc.

Jpn,55,3766-3769.

Additional information

On contact with water calcium bis(metaphosphate) will dissociate to calcium cations and phosphate anions. A determination of the hydrolysis of the calcium cation and the phosphate anion according to OECD guideline 111 was not conducted since both ions have no potential mechanism for further hydrolysis or degradation.

The hydrolysis of well soluble sodium tripolyphosphate was investigated in sterile aqueous buffers at pH 3, 4, 5 and 7, and at temperatures between 40 and 70 °C, by Zidner, Hertz and Oswald (1984). The experimental data were in good agreement with the following mechanism and gave a pseudo first-order reaction law.

P3O105- + H2O → PO43- + P2O74- + 2 H

P2O74- + H2O →2 O43- + 2H+

In sterile water the predicted half-life of triphosphate at pH 7-8 and at 20 °C is in the order of years.

The kinetics of hydrolysis of triphosphate and pyrophosphate were also studied in sterile lake water and sterile algal culture media and in non-sterile media at 25 °C by Clesceri and Lee (1965a, 1965b),and compared to published results obtained in distilled water. The results showed that triphosphate and pyrophosphate were hydrolysed in orthophosphate in a period of several days. Addition of glucose increased the rate of hydrolysis, indicating that microbial activity was one of the primary mechanisms of hydrolysis.

The hydrolytic half-life anticipated for the anions of specified phosphates, pyrophosphates and triphosphates has been addressed by read across from a single example for each chemical class, where applicable. The ionic substances were assumed to undergo dissociation in aqueous solution and the resulting cation to have negligible influence on the hydrolysis rate of the anion within the buffer solutions used as instructed by Method 111 of the OECD Guidelines (Harlan, 2011).

The available data demonstrate that triphosphates and triphosphates are hydrolytically stable under environmental conditions with a half-life > 1 year.

Chemical Class	Substance Used for Experimental Determination	Anticipated Half-Life at 25°C
Phosphates Orthophosphates	Not applicable, no possible mechanism for hydrolysis	N/A
Pyrophosphates Diphosphates	Tetrapotassium Pyrophosphate CAS 7320-34-5	pH4 > 1 year pH 7 > 1 year
Triphosphates Tripolyphosphates	Pentapotassium Triphosphate CAS 13845-36-8	pH 9	> 1 year
		pH4 pH 7	14.5 days > 1 year
		pH 9	> 1 year

 

References:

Clesceri N.L. and Lee G.F. (1965a) Hydrolysis of Condensed Phosphates – II : Sterile Environment, Int. J. Air Wat. Poll. 9, 743-751.

Clesceri N.L. and Lee G.F. (1965b) Hydrolysis of Condensed Phosphates – I : Non-Sterile

Zinder B., Hertz J. and H. R. Oswald (1984) Kinetic Studies on the Hydrolysis of Sodium Tripolyphosphate in Sterile Solution, Water Res. 18 (5), 509-512.