Dipotassium 3,4,5,6-tetrabromophthalate

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

The substance falls outside the applicability domain in view of being a salt.

The acid form can be put through (Q)SAR, and although this will provide an unreliable assessment for the substance as supplied, it will have some implications for risk assessment.

The potassium salt will dissociate in the environment and is likely to re-combine with other ions, depending on the pH (eg Ca or Mg)

Under acid conditions, such as if ingested, the acid form will exist and is the basis for read-across. The data generated for the anhydride will apply to the acid form; the anhydride readily converts to the acid in the presence of water.

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Justification for type of information:

Performed by Lead Registrant in-house using calibrated equipment.
Information was generated to help support observations from environmental testing and to confirm suspected solublity under environmental and biological conditions.

Qualifier:

no guideline available

Principles of method if other than guideline:

The substance was disolved in two types of commercially available bottled water of known hardness, pH and analysis and concentrations up to 100 mg/l.
The substance was dissolved in molar HCl (ca pH1) at up to 100 mg/l
Precipitation of insoluble salts/acid was determined by use of a calibrated turbidity meter

GLP compliance:

no

Other quality assurance:

other: Use of calibrated instrumentation

Type of method:

flask method

Water solubility:

< 5 mg/L

Conc. based on:

other: estimation in considering presence of undisolved material

Loading of aqueous phase:

100 mg/L

Incubation duration:

ca. 1 h

Temp.:

20 °C

pH:

> 6.7 - < 7.4

Water solubility:

< 5 mg/L

Conc. based on:

other: estimation in considering presence of undisolved material

Loading of aqueous phase:

100 mg/L

Incubation duration:

ca. 1 h

Temp.:

20 °C

pH:

ca. 1

Details on results:

The measured pH for the mineral water was based on analysis provided by the suppliers.
The test substance did not impact on the pH.
The figure of 5 mg/l cited for solublity is based on report solublity for the acid form. Turbity was considered hardly detectable at < 10 mg/l

Conclusions:

The substance showed low solubiilty when diluted to below 100 mg/l in water typically used for ecotoxocity testing
The substance showed low solublity when diluted at pH 1 to mimic possible effects if ingested.
Acutal solubility was not possible to establish since it was in equilibrium

Executive summary:

Standard testing to EC A6 method demonstrated very high water solubility / miscibility with a slightly alkaline pH 9.9.

 

However, under dilute conditions in 'natural' water (as required for environmental toxicity testing), the substance proved to be poorly soluble with the apparent formation of calcium and other salts from the hardened test water. The apparent solubility decreased as concentrations were reduced. A solubility limit of ca 5 mg/l is reported in environmental toxicity testing for tetrabromophthalate salts.

 

It is likely that under these dilute conditions, the salt will exist in equilibrium and apparent solubility will depend greatly on actual hardness of the water and also the pH

 

Further work (Report, Dixon Chew, 19 March 2020) demonstrated precipitation under diluted conditions at pH 1 or in natural water (assessed by turbidity), thus confirming dissociation with formation of insoluble salts (natural water) and also formation of the poorly soluble acid form (pH 1, molar HCl). Although this work was non-quantitative in terms of determining actual solubility under these conditions, the observations demonstrated that the potassium salt will behave in the same way as the acid form under environmental and biological conditions.

 

These conclusions need to also be considered in the light of the well established observations that the anhydride quickly hydrates to the acid form under similar environmental conditions. Likewise, research has shown that the alkyl esters also hydrolyse to the acid form under environmental conditions. 

 

It must also be noted that the functionality of these substances is to provide the same propertied to different fabrics for fire retardant properties. The purpose of creating alkyl esters, or water soluble potassium salts is to allow use in different textile treatment media, but the functionality come from the C-O and C=O bonds of the phthalate to adhere to proteins and other charged groups in wool and other fibres. 

Data source

Reference

Reference Type:

other company data

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

other: Koc Estimate from MCI

Principles of method if other than guideline:

Use of EPISuite
The acid hasbeen assessed as the sodium salt will not be applicable to the modelling methods
The acid form can be put through (Q)SAR, and although this will provide an unreliable assessment for the substance as supplied, it will have some implications for risk assessment.

The potassium salt will dissociate in the environment and is likely to re-combine with other ions, depending on the pH (eg Ca or Mg)

Under acid conditions, such as if ingested, the acid form will exist and is the basis for read-across. The data generated for the anhydride will apply to the acid form; the anhydride readily converts to the acid in the presence of water.

GLP compliance:

no

Remarks:

GLP is not applicable for QSAR estimates

Type of method:

other: Caculation

Test material

Test material information

Constituent 1

Reference substance name:

Tetrabromophthalic acid

Cas Number:

13810-83-8

Molecular formula:

C8H2Br4O4

IUPAC Name:

Tetrabromophthalic acid

Specific details on test material used for the study:

The acid form can be put through (Q)SAR, and although this will provide an unreliable assessment for the substance as supplied, it will have some implications for risk assessment.

The potassium salt will dissociate in the environment and is likely to re-combine with other ions, depending on the pH (eg Ca or Mg)

Under acid conditions, such as if ingested, the acid form will exist and is the basis for read-across. The data generated for the anhydride will apply to the acid form; the anhydride readily converts to the acid in the presence of water.

Radiolabelling:

no

Study design

Test temperature:

Model calibrated for 20 C

Results and discussion

Adsorption coefficient

Sample No.:

#1

Type:

log Koc

Value:

ca. 2.7

pH:

7

Temp.:

20 °C

Remarks on result:

other: Normal modelling parameters used.

Any other information on results incl. tables

It is noted that the outcome will be pH dependant.

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

The acid has been assessed since it is expected that the potassium salt will dissociate in the environment with ion exchange.
In reality, adsorption to soild and sediment will be very pH dependant with ion exchange likely with Ca and Mg in soils and hard water.

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