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Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012
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:
Spectrophotometry of different aqueous extract from the powder
GLP compliance:
no
Type of method:
other: spectrophotometry
Key result
Water solubility:
< 0.01 mg/L
Conc. based on:
test mat.
Temp.:
25 °C
Remarks on result:
other: pH not mentionned in the study

 Table I: Calculated concentrations for a 0.45 µm filtration.

Test 1

1 g of dye

Test 2

2 g of dye

Test 3

4 g of dye 

 

Visual (powder + water)

Light yellow

Light yellow

Light yellow

 

Filtration

Porosity of 0.45 µm

Porosity of 0.45 µm

Porosity of 0.45 µm

Number of dilution

2

2

2

Spectrometry results

 

(Spectro DU640

BECKMAN)

AY 36

DO 425 nm = 0.0841 u.Abs

DO 425 nm = 0.1413 u.Abs

DO 425 nm = 0.2541 u.Abs

BV3

DO 588 nm = 0.0079 u.Abs

DO 588 nm = 0.0308 u.Abs

DO 588 nm = 0.0560 u.Abs

Calculated concentrations

AY 36

Conc. en AY36 = 2.34 mg/L

Conc. en AY36 = 3.93 mg/L

Conc. en AY36 = 7.058 mg/L

BV3

Conc en BV3 = 0.057 mg/L

Conc en BV3 = 0.225 mg/L

Conc en BV3 = 0.409 mg/L

 

Observation: In this case, both the cation and the anion are found in the aqueous extract with a clear excess of AY 36. The more SBl 46 is added at the beginning, the more the final AY 36 concentration is increasing.

During the SBl 46 synthesis, the Basic Violet 3 quantity put in the reactor is adjusted with the AY36 quantity so as to aim equilibrium between both ions. However one of the two ions may be in slight excess at the end of the process. Very often, it happens to be the AY 36 that will then be found in the aqueous extract under its ionic form. AY 36 and BV3 cannot coexist in water.

 

Conclusion: SBl 46 is not soluble in water. The presence of BV3 in the extract can be explained by small particles of SBl 46 that have been allowed to go through the filtering membrane (0.45µm). The dilution step with methanol solubilizes those particles.

 

To confirm this hypothesis, a more stringent filtration will be performed: 0.2 µm thanks to a cellulose acetate membrane.

 From the calculated concentrations, the quantity of "soluble matter" with reference to the SBl 46 is calculated, considering that the ion which is not in excess can stem only from the SBl 46.

 

Table II: Calculated concentrations for a 0.20 µm filtration.

 

Test 1

1 g of dye

Test 2

2 g of dye

Test 3

4 g of dye 

 

Visual (powder + water)

Light yellow

Light yellow

Light yellow

 

Filtration

Porosity of 0.20 µm

Porosity of 0.20 µm

Porosity of 0.20 µm

Number of dilution

2

2

2

Spectrometry results

 

(Spectro DU640

BECKMAN)

AY 36

DO 425 nm = 0.0798 u.Abs

DO 425 nm = 0.1305 u.Abs

DO 425 nm = 0.2411 u.Abs

BV3

DO 588 nm = 0.0006 u.Abs

DO 588 nm = 0.00120 u.Abs

DO 588 nm = 0.0134 u.Abs

Calculated concentrations

AY 36

Conc. en AY36 = 2.22 mg/L

Conc. en AY36 = 3.63 mg/L

Conc. en AY36 = 6.70 mg/L

BV3

Conc en BV3 = 0.004 mg/L

Conc en BV3 = 0.008 mg/L

Conc en BV3 = 0.097 mg/L

Quantity of soluble matter with reference to the SB 46.

0.004 x 725/408 = 0.007 mg/L

0.088 x 725/408 = 0.15 mg/L

0.097 x 725/408 = 0.17 mg/L

Observation: with the 0.2 µm filtration, the BV3 concentration has been seriously reduced except for the third assay where the BV3 concentration is near 0.1 mg/L. This concentration can be explained again by small particles going through the filter. Indeed the powder contains particles < 0.2 µm.

The concentration drop is observed in similar proportion between the both constituents of the SBl 46, i.e. AY 36 and BV3, and the SBl 46 itself. This demonstrates that the 0.20 µm filtration retains more effectively particules of the SBl 46.

 

           In the filtrate-0.45 µm :                  7.06 mg/L of AY36 so 18.83 millimoles of AY36

                                                               0.409 mg/L of BV3 so 1.002 millimoles of BV3

 

           In the filtrate-0.20 µm :                  6.70 mg/L of AY36 so 17.87 millimoles of AY36

                                                               0.097 mg/L of BV3 so 0.238 millimoles of BV3

 

           Keeping in on the 0.2 µm filter :     18.83 – 17.87 = 0.96 millimoles of AY36

                                                                1.002 - 0.238 = 0.76 millimoles of BV3

CONCLUSION:

Although a 0.20 µm filtation membrane is used, some particles solubilized during the dilution step by methanol are remaining. As for the assay performed with a 0.45 µm filtation, the AY 36 is the ion in excess, to the BV3 is the ion representative of the solubilized portion of SBl 46.

It has been demonstrated that the more SBl 46 is added, the more the final AY 36 concentration is increasing. What is principally (even totally) measured is the presence of thin particules which pass through the filter and that has been solubilized by the methanol.

It is therefore not possible to distinguish what has been measured: soluble particles of SBl 46 or secondary solubilization of insoluble particles solubilized by the methanol.

In any case, it can be concluded that the solubilty of SBl 46 is less than 0.01 mg/L or even not existing.

Conclusions:

Despite the 0.2 µm filter used, some small particles of Solvent Black 46 are still present and dissolved by the methanol in the final matrix. Using the lowest starting SBl 46 concentration (1 mg/L), the ions concentration have been respectively measured as 2.22 mg/L and 0.004 mg/L. Both ions cannot co-exist in water.Therefore, if the AY 36 is in excess, the BV3 is the ion representative of the SBl 46 solubility. It is not possible to distinguish what has been measured: soluble particles of SBl 46 or secondary solubilisation of insoluble particles solubilized by the methanol.

In any case, it can concluded that the solubilty of SBl 46 is less than 0.01 mg/L or even not existing.

Description of key information

The substance is hydrophobic, of which the hydrosolubility is protocol-dependent.

Key value for chemical safety assessment

Water solubility:
0.01 mg/L
at the temperature of:
20 °C

Additional information

The substance is a co-precipitate of Acid Yellow 36 (AY36) and Bacic Violet 3 (BV3) as defined in section 1 of the IUCLID dossier with a ratio of 1:1.

AY 36 represents the anionic part and BV3 represents the cationic part.

The substance has no specific absorbance and is therefore identified by the respective absorbance of BV3 and AY36.

In normal conditions, there is no dissociation of the substance, thus when both concentrations (BV3 and AY36) are measured as equivalent, it should correspond to the concentration of the entire molecule.

Previous measurements have been performed and have shown that both BV3 and AY 36 could be found as impurities, leading to an excess of one of the starting material, but AY 36 and BV3 cannot coexist in water.

So the observed excess of AY 36 is coming from an excess of AY 36 during the manufacturing process, although the manufacturing process is designed to be under stoichiometric conditions (and also despite the purification steps that should have removed all the soluble components). The presence of BV3 in the extract can be explained by small particles of SBl 46 that have been allowed to go through the filtering membrane (0.20 µm). The dilution step with methanol solubilizes those particles.

It is therefore not possible to distinguish what has been measured: soluble particles of SBl 46 or secondary solubilisation of insoluble particles solubilized by the methanol.

This finding implies that the hydrosolubility of the substance is either not existing or existing but less than 0.01 mg/L.

A OECD TG 123 study on the substance is available. In this study, the mean measured concentration of the substance in the aqueous solution (water saturated with octanol) was determined to be of 0.0381 mg/L. Also this study is not designed to test the water solubility of a substance, the result of this study supports the very low water solubility of the substance determined in the internal study, as the water solubility of the substance is expected to be slightly higher in a such test since the water is saturated with octanol, increasing its water solubility.

Therefore, in the chemical safety report, the value of 0.01 mg/l is used to predict emission concentration (PEC) to the aquatic compartment and to calculate the Log Kow.