5-hydroxyiminobarbituric acid

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

August 2014

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The solubility of violuric acid was determined at different pH by dissolving violuric acid in water or buffer or sodium hydroxide followed by shaking at 25 or 50°C for up to 14h. Hereafter the samples were centrifuged and filtrated to remove insolubles, pH measured and concentration of violuric acid measured with absorbance at 550nm and compared to a reference violuric acid of 1.75 g/L.

Experiment 1
0.4 g violuric acid monohydrate in 10 mLwater or buffer followed by incubation with shaking for 14 hours at 50 °C and afterwards reduced heat to 25 °C and continued shaking for 2 hours.Centrifugation of the tubes at 25 °C for 5 minutes and removal of supernatant.Filtration to remove insolubles and measurement of pH. Herafter 5 times dilution in 100 mM disodiumhydrogen phosphate and measurement of absorbance at 550 nm and comparision to a reference violuric acid of 1.75 g/L (10 mM) in 100 mM disodiumhydrogen phosphate.

Experiment 2
0.4 g violuric acid monohydrate in 10 mLwater or sodium hydroxidefollowed by incubation with shaking for 1 hour at 25°C. Centrifugation of the tubes at 25 °C for 5 minutes and removal of supernatant.Filtration to remove insolubles and measurement of pH. Herafter 5 times dilution in 100 mM disodiumhydrogen phosphate and measurement of absorbance at 550 nm and comparision to a reference violuric acid of 1.75 g/L (10 mM) in 100 mM disodiumhydrogen phosphate.
23. Incubate with shaking for 1 hours at 25 °C

Experiment 3
0.438 g violuric acid monohydrate in 25 ml sodium hydroxide/buffer mixture.Incubation with shaking for 1 hour at 50 °C and afterwards reduced heat to 25 °C and continued shaking for 1 hours.Centrifugation of the tubes at 25 °C for 5 minutes and removal of supernatant.Filtration to remove insolubles and measurement of pH. Herafter 5 times dilution in 100 mM disodiumhydrogen phosphate and measurement of absorbance at 550 nm and comparision to a reference violuric acid of 1.75 g/L (10 mM) in 100 mM disodiumhydrogen phosphate.


Violuric acid reference: Dissolve 175 mg violuric acid monohydrate in 100 mL 100 mM disodiumhydrogen phosphate

GLP compliance:

no

Key result

Water solubility:

ca. 8 g/L

Conc. based on:

test mat. (dissolved fraction)

Temp.:

20 °C

pH:

ca. 3

Details on results:

Experiment 1 Experiment 2 Experiment 3
pH g/L pH g/L pH g/L
2.91 8.4 2.89 7.7 4.42 5.3
3.48 8.6 4.24 12.8 5.34 8.3
3.56 9.0 4.2 12.0 5.5 16.0
3.73 9.5 4.69 10.1 6.3 17.4
3.92 10.6 5.79 15.3 7.01 17.2
3.54 8.8 5.69 22.4 7.39 17.5
3.38 9.1 - - - -
3.25 9.5 - - - -
3.22 9.8 - - - -
3.17 10.4 - - - -

Conclusions:

Solubility of violuric acid is dependent on pH and in pure water the pH ends in less than 3 and solubility is ca. 8g/L.

Executive summary:

Violuric acid has limited solubility in the acid form. In pure water the pH ends at less than 3 and solubility is

around 40-50 mM (8 g/liter). Titration of the acid to the violurate form is required to increase solubility.

Too much sodium hydroxide apparently degrades violuric acid and form a reddish compound that,

however, may not be very soluble. A maximum solubility was not determined since it may require slow

titration rather than a one step reaction.

The suggested conditions for a 100 mM solution of violuric acid (17.5 g/liter) is 60 mM sodium hydroxide

and 50 mM dibasic sodium phosphate. This mixture is soluble at both 50 and 25 °C and have a pH of about

6.3.

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018-05-30 to 2018-08-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995

Deviations:

no

GLP compliance:

yes

Type of method:

flask method

Key result

Water solubility:

7.04 g/L

Conc. based on:

act. ingr.

Loading of aqueous phase:

52 g/L

Incubation duration:

3 d

Temp.:

20 °C

pH:

3

Remarks on result:

other: Average of day1, 2 and 3. Standard deviation was 0.107. Equilibrium reached at 24h.

Conclusions:

The water solubility of violuric acid at 20°C is 7.04g/L.

Executive summary:

The water solubility of violuric acid was determined according to OECD Test Guideline 105 with the flask method.

Duplicate samples were prepared and analysed with HPLC after 24, 48 and 72h. Equilibrium was reached after 24h and the average concentration of the violuric acid was 7.04 +/- 0.127 g/L at 20°C.

Description of key information

The water solubility of violuric acid was assessed in House under different pH conditions and according to OECD test guideline no. 105 at the Chemicals Evaluation and Research Institute in Japan (CERI). The internally obtained results indicate a water solubility of 8g/L and according to OECD TG water solubility of violuric acid at 20°C is 7.04g/L. The results from CERI obtained according to current OECD test guidelines are used for the water solubility of violuric acid.

Key value for chemical safety assessment

Water solubility:

7.04 g/L

at the temperature of:

20 °C