Phosphotungstic acid

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 435 (In Vitro Membrane Barrier Test Method for Skin Corrosion)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Tungstate(3-), tetracosa-μ-oxododecaoxo[μ12-[phosphato(3-)-κO:κO:κO:κO':κO':κO':κO'':κO'':κO'':κO''':κO''':κO''']]dodeca-, hydrogen, hydrate (1:3:?)

EC Number:

603-020-3

Cas Number:

12501-23-4

Molecular formula:

H3PW12O40 * xH2O

IUPAC Name:

Tungstate(3-), tetracosa-μ-oxododecaoxo[μ12-[phosphato(3-)-κO:κO:κO:κO':κO':κO':κO'':κO'':κO'':κO''':κO''':κO''']]dodeca-, hydrogen, hydrate (1:3:?)

Test material form:

solid

In vitro test system

Test system:

artificial membrane barrier model

Vehicle:

unchanged (no vehicle)

Details on test system:

The Corrositex® assay is a standardized in vitro corrosion test. The Corrositex® assay kit is commercially available from InVitro International.
The Corrositex® Biobarrier Membrane is a test system consisting of a reconstituted collagen matrix. The assay is based on the time that the test substance requires to penetrate through the Corrositex® Biobarrier Membrane and produce a change in the Chemical Detection System (CDS).
The Corrositex® assay is used to determine the corrosive potential of test substances. The assay is limited to testing materials which cause detectable pH changes in the CDS.

The experimental design of this study consisted of a qualification screen with the CDS (to determine if a color change can be detected) and a categorization screen (to categorize weak acids/bases and strong acids/bases) which were performed as a pretest (experimental conduct in accordance with GLP, but without a GLP status) and a definitive Corrositex® assay.
The Corrositex® assay was evaluated on the basis of the color change of the CDS. The time until a color change was observed was recorded manually and the breakthrough times of the four replicates were used to determine the corrosive potential of the test substance.

Test substance compatibility with the assay (qualification screen): For the qualification screen, 100 mg of the test substance were added to the CDS screening tube. If the test substance failed to produce a color change in the CDS within one minute the test substance could not be analyzed in this system and no further testing was required.

Categorization screen: The categorization screen was used to assess the appropriate scoring scale for the test substance.
The categorization screen was performed by adding 100 mg of test substance to tube A and B each. Each tube was mixed and the resulting color was observed. If required, 2 drops of the "confirm" reagent were added to tube B, the tube was mixed and the resulting color was observed.
The categorization kit and color chart provided by InVitro International were used to determine the category. The test substance was scored as category 1 (high acid/alkaline reserve) or category 2 (low acid/alkaline reserve).

Corrositex® assay
Following the acceptance of the positive control, the Corrositex® assay was performed for the test substance. Four vials containing the CDS were used for the test substance. In addition, one vial was used for the PC, the NC and the color (blank) control each. A membrane disc coated with the biobarrier matrix was placed into one vial containing the CDS. 500 mg undiluted test substance were added onto the membrane disc. An electronic time clock was started with the application. The vial was observed for three minutes for any change in the CDS. If no color change was observed within three minutes, the remaining membranes were treated with the test substance. An electronic time clock was started with each application. The vials were continuously observed for the first ten minutes. Thereafter, the vials were observed for approximately ten minutes around the time points relevant for evaluation or until breakthrough of the test substance occurred. The elapsed time between test substance application and the first change in the indicator solution (i.e. barrier penetration) was recorded.

positive control: one pellet of sodium hydroxide on top of the membrane disc. This vial was continuously monitored until breakthrough occurred.
negative control: 500 μL 10% citric acid. This vial was observed for 60 minutes and evaluated as “non-corrosive” if no reaction could be observed.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

500 mg undiluted test substance

Duration of treatment / exposure:

up to 4 hours or until breakthrough

Number of replicates:

4

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

penetration time (in minutes)

Run / experiment:

4 replicates

Value:

55.25

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

Qualification screen: the test substance can react with the CDS and produce a visible color change.

Categorization screen: the test substance was assigned to timescale category 2 (having a low acid/alkaline reserve).

Breakthrough times of the test substance and the PC and NC

Test substance	Break Through Time [min:s]
	Vial 1	Vial 2	Vial 3	Vial 4	Mean
16/0488-1	58:10	54:08	54:26	54:16	55:15
Controls:
PC: Sodium hydroxide, solid	10:46	-	-	-	-
NC: 10% citric acid	NB	-	-	-	-

NB = no breakthrough within maximum observation period (60 min)

Applicant's summary and conclusion

Interpretation of results:

Category 1C (corrosive) based on GHS criteria

Conclusions:

Based on the results observed and by applying the evaluation criteria, it was concluded that Phosphorwolframic acid hydrate shows a corrosive potential in the Corrositex® - Skin Corrosion Test under the test conditions chosen. The mean breakthrough time determined in the in vitro membrane barrier test was 55 minutes and 15 seconds. -> GHS Cat. 1C