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Water solubility

Administrative data

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-12-13 - 2019-01-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

OECD Guidelines for the Testing of Chemicals, Method No. 105, adopted 27. Jul. 1995: “Water Solubility“

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

Commission Regulation (EU) No 260/2014 amending Regulation (EC) No 440/2008: Method A.6: “Water solubility", adopted 24 January 2014

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Test material

Test material information

1

Reference substance name:

Reaction product of Graphite, acid-treated and potassium permanganate

IUPAC Name:

Reaction product of Graphite, acid-treated and potassium permanganate

Test material form:

cream / paste

Results and discussion

Water solubility

Water solubility 1

Water solubility:

166 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

1 008 mg/L

Incubation duration:

3 d

Temp.:

20 °C

pH:

>= 5 - <= 6

Water solubility 2

Water solubility:

278 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

3 000 mg/L

Incubation duration:

3 d

Temp.:

20 °C

pH:

>= 5 - <= 6

Water solubility 3

Water solubility:

364.5 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

5 040 mg/L

Incubation duration:

3 d

Temp.:

20 °C

pH:

>= 5 - <= 6

Water solubility 4

Water solubility:

412.7 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

6 064 mg/L

Incubation duration:

3 d

Temp.:

20 °C

pH:

>= 5 - <= 6

Details on results:

The solubility of Graphene oxide, reaction product of Graphite, acid-treated and potassium permanganate in water was determined from the measured concentrations of DOC in the filtrated test solutions.The carbon content of the test item of 25.42 % was used in the calculation of the test item concentration from the measured DOC concentration.
In the main test, six different loading rates in the range of 1 – 10 g/L were chosen. The higher range was chosen as the measured value in the solution with the nominal load 1 g/L during the preliminary test was approx. 50 mg/L TOC (low concentration). As a dependency of the solubility of the test item on the nominal load was expected in the main test, higher measured values were expected in the high nominal loads.
Linear dependency of the solubility on the amount of the test item (nominal load) was perceived in the flasks 1 – 4 only. The flasks 5 – 6 were not used in the evaluation as the values lay outside the linear range probably due to high nominal loads (the filtration of the solutions was were difficult).
As the solubility was dependent on the nominal concentration, no exact value for the solubility of the test item in water can be stated. The solubility range for the tested nominal concentrations 1 – 6 g/L is 166.0 – 412.7 mg/L, corresponding to a dissolved part of 16.5 – 6.8 % of the test item relating to the nominal concentration of the test item.
Dependency of the pH value on the amount of the test item (nominal load) was not perceived.
No observations arousing doubts concerning the accuracy of the results and the validity of the study were made.

Applicant's summary and conclusion

Conclusions:

The study was conducted under GLP according to OECD TG 105 and EU Method A.6 without deviations and therefore reliability of Klimisch 1 has been assigned. Based on the obtained results the solubility of Graphene oxide, reaction product of Graphite, acid-treated and potassium permanganate in water was determined to be 166.0 – 412.7 mg/L at 20.0 °C for the following nominal concentration range of the test item in water: 1 – 6 g/L, corresponding to a dissolved part of 16.5 – 6.8 % of the test item relating to the nominal concentration of the test item.

Executive summary:

The study was performed under GLP according to OECD 105 and EU Method A.6.The solubility of the test item Graphene oxide, reaction product of Graphite, acid-treated and potassium permanganate in water was determined by measurement of the DOC concentration in the filtrated test solutions using a TOC analyser.

In the pre-test, flasks with nominal concentrations of 10 mg/L and 1000 mg/L were shaken at room temperature for 93 h and measured for DOC after membrane filtration (0.45 µm, nylon). Undissolved particles were observed in the 1000 mg/L test item solution only. The measured DOC concentration lay at 47.4 mg/L after subtraction of the blank value in the 1000 mg/L test item solution. As dependency of the water solubility on the amount of the test item added may be observed for such substances as the test item, different loading rates were used in the main test. According to the guideline, the flask method was used for the determination of the solubility of the test item in water.

In the main test,six different loading rates of the test item were chosen to study the effect of the loading rate on the measured water solubility: 1, 3, 5, 6, 8 and 10 g/L. Three flasks (1A – 1C) with the same loading rate (5 g/L) were used during equilibration. Seven vessels (flasks blank, 1C (for the sampling point 72 h) and 2 – 6) were set onto the shaking apparatus immediately and shaking at 100 rpm was started. After 24 ± 2 hours, flask 1B (for the sampling point 48 h) and after 48 ± 2 hours, flask 1A (for the sampling point 24 h) were set on the shaker and all flasks were shaken for further 24 ± 2 hours at room temperature. Then, flasks 1A – 1C were removed from the shaker, tempered at 20.0 ± 0.5 °C, samples were taken, membrane filtered and analysed for DOC via TOC analyser. Due to a difference of less than 15 % in the concentrations on days 2 and 3 and no upward tendency in the three values, the test was finished on day 3. The final measurement was performed on day 3 as determination from flasks 2 – 6. DOC was measured via a TOC analyser in the saturated aqueous solutions. The pH value in the flasks 2 – 6 lay in the range of 5.02 – 5.96.

No Tyndall effect (i.e. a laser beam was not scattered when transmitted through the liquid) could be observed indicating that no colloidal dispersed particles were present.

Linear dependency of the solubility on the amount of the test item (nominal load) was perceived in the flasks 1 – 4 only. The flasks 5 – 6 were not used in the evaluation as the values lay outside the linear range probably due to high nominal loads (the filtration of the solutions was difficult).

As the solubility was dependent on the nominal concentration, no exact value for the solubility of the test item in water can be stated. Dependency of the dissolved part on the amount of the test item (nominal load) was also perceived in the main test.

Therefore, the concentration of the test item in water was stated as: 

166.0 – 412.7 mg/L at 20.0 °C

166.0 – 412.7 * 10^-3kg/m³(SI units)

for the following nominal concentration range of the test item in water: 1 – 6 g/L, corresponding to a dissolved part of16.5 – 6.8 %of the test item relating to the nominal concentration of the test item.