Tetrakis(hydroxymethyl)phosphonium sulphate(2:1)

Oxidising properties

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

oxidising liquids

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the organic substance contains oxygen or halogen atoms which are chemically bonded only to carbon or hydrogen and hence, the classification procedure does not need to be applied

Reference 2

Endpoint:

oxidising liquids

Type of information:

other: expert statement

Adequacy of study:

other information

Study period:

16th December 1999

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

secondary literature

Principles of method if other than guideline:

Method: expert statement

GLP compliance:

no

THPS is a mild reducing agent as the phosphorus atom in the chemical structure is in an oxidation state of 3 and the most stable oxidation state for phosphorus is 5. There is therefore the potential for reaction with oxidising agents which will convert the phosphorus to the higher oxidation state.

Two examples where THPS reacts easily with an oxidising agent illustrate this point:.   

- THPS is easily oxidised by a variety of common oxidising agents, including chromate and hydrogen peroxyde. It can therefore not be an oxidising agent ; otherwise it would oxidise itself,

At typical biocidal use dilute concentrations, THPS will react with dissolved oxygen in water to form THPO. THPO is a fairly stable compound and is neither an oxidising nor a reducing agent. - The preferred method of measuring THPS concentration is by titration with iodine. The rationale behind the method is that the iodine quantitatively oxidises the THPS to trishydroxymethylphosphine oxide (THPO) stoichiometrically.

As illustrated above, THPS typically acts as a mild reducing agent, rather than an oxidising agent.

Interpretation of results:

GHS criteria not met

Conclusions:

As demostrated, THPS typically acts as a mild reducing agent, rather than an oxidising agent.

Executive summary:

A reliable expert statement based on the active substance chemistry and reactions have been developed.

- The oxidation state of the phosphorous in THPS is 3, i.e. the lower oxidation state. The most stable oxidation state for phosphorus is 5. There is therefore the potential for reaction with oxidising agents which will convert the phosphorus to the higher oxidation state. This chemistry means that THPS is not an oxidising agent, it is actually a mild reducing agent.

- THPS is easily oxidised by a variety of common oxidising agents, including chromate and hydrogen peroxyde. It can therefore not be an oxidising agent ; otherwise it would oxidise itself. At typical biocidal use dilute concentrations, THPS will react with dissolved oxygen in water to form THPO. THPO is a fairly stable compound and is neither an oxidising nor a reducing agent.

-The preferred method of measuring THPS concentration is by titration with iodine. The rationale behind the method is that the iodine quantitatively oxidises the THPS to trishydroxymethylphosphine oxide (THPO) stoichiometrically.

As illustrated above, THPS typically acts as a mild reducing agent, rather than an oxidising agent. It cannot therefore be classed as an oxidising agent.

Description of key information

No experimental test is available for oxidising properties however, no study need to be conducted because the organic registered substance contains oxygen atoms which are chmically bond only to carbon or hydrogen and hence, it could be conclude that THPS is not oxidising.

Key value for chemical safety assessment

Oxidising properties:

non oxidising

Additional information

A non assignable expert statement based on the active substance chemistry and reactions have been developed to demonstrate that THPS typically acts as a mild reducing agent and is not an oxidising agent (Talbot, 1999).

Justification for classification or non-classification

No experimental test is available for oxidising properties however, no study need to be conducted because the organic registered substance contains oxygen atoms which are chemically bond only to carbon or hydrogen and hence, it could be concluded that THPS is not oxidising for classification (CLP) purposes.

Further, a non assignable expert statement based on the active substance chemistry and reactions have been developed to illustrate that THPS typically acts as a mild reducing agent, rather than an oxidising agent.