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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:
report date: 2010-02-18
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
no
Type of method:
flask method
Water solubility:
4.2 g/L
Temp.:
20 °C
pH:
> 5.6 - < 6.2
Details on results:
PRELIMINARY TEST:
A preliminary test at ambient temperature was performed to provide an estimation of the solubility. 0.1 g of 4-TBC was placed in a 10 mL glass-stoppered measuring cylinder. After each addition of water, the mixture was shaken for 10 minutes and was visually checked for any undissolved parts of the sample.

After additions completed to 10 mL of water, parts of the sample remained undissolved. The experiment was then continued in a 100 mL measuring cylinder. After 24 hours, the sample was completely dissolved in 100 mL of water. After 24 hours of assay, a clear orange color was observed.

The approximate solubility established by this attempt was between 1 and 10 g per liter, according to the OECD recommendations. Thus, a second more precise preliminary test was performed. 0.1 g of 4-TBC was placed in a 100 mL tared glass flask with a mantle and a magnetic stirrer. Small amounts of water (about 1g) were added step by step until reaching total solubility of 4-TBC. The ratio between the mass of 4-TBC and added water gives a solubility of 4-TBC around 5 g per liter. An orange coloration was observed when the limit of solubility is reached.

FLASK METHOD:
A solution of 4-TBC was prepared with a concentration of 5 g of 4-TBC in 500 mL of water. This solution was transferred in three identical appropriate cells maintained at 30 °C for respectively one, two and three days under constant shaking. After this first stage at 30 °C, the samples were equilibrated for 24 hours at the test temperature (20 °C) with occasional shaking. Each sample was analyzed three times, except sample 1 (one day of stirring) analyzed 4 times due to data variability.
pH of each sample was also measured.

As for the preliminary tests, coloration (orange) of the test samples was observed. Based on the low variability of the analytical results reported in Table 2, it was considered that 4-TBC was on a steady-state with the test medium since the first day of stirring. Therefore, it was concluded that this observation did not change the conclusion of the test.


The average solubility is 4.2 grams per liter with a standard deviation of 0.5 gram per liter. The concentrations measured in the two last vessels do not differ by more than 15% (11.6%); therefore, the test is considered as valid.

Results of the three samples left one, two and three days at 30°C are given in the following Table 2.

Before analyses, the samples are centrifuged at 3800 round per minute during 20 minutes.

Table 2: Results of the water solubility test on 4-TBC at 20°C:

Sample (stirring time)

Solubility

(g/L)

Average Solubility per sample (g/L)

Standard deviation

(g/L)

pH

One day

5.06

4.14

0.68

6.2

 

3.56

 

 

 

3.70

 

 

 

4.26

 

 

Two days

4.41

3.97

0.40

6.1

 

3.64

 

 

 

3.85

 

 

Three days

4.66

4.49

0.15

5.6

 

4.35

 

 

 

4.46

 

 

Conclusions:
Interpretation of results: soluble (1000-10000 mg/L)
The water solubility of 4-tert-butylpyrocatechol at 20°C is 4.2 g/L +/- 0.5 g/L.
Executive summary:

In a study (Processium, 2010), the water solubility of 4 -tert-butylpyrocatechol (4 -TBC) was determined by GPC method and using the flask method, according to the regulation (EC) n°440/2008, A.6 and the OECD Guideline n°105.

Two preliminary tests were performed and indicated that the test item was soluble in water wtih a solubility above 5g/L.

The concentrations were determined after a shaking time of 24, 48 and 72 hours, respectively at 30°C. Afterwards the samples were equilibrated for another 24 hours at 20°C.

The solubility of 4 -tert-butylpyrocatechol in water was 4.2 g/L +/- 0.5 g/L (standard deviation) at 20°C.

This study is classified as acceptable and satisfies the guideline requirements for a water solubility study.

Description of key information

Water solubility at 20°C: 4.2 g/L +/- 0.5 g/L

Key value for chemical safety assessment

Water solubility:
4.2 g/L
at the temperature of:
20 °C

Additional information

One experimental study (Processium, 2010) with reliability 1 according to Klimisch was available and was selected as key study. Water solubility was determined by GPC method and using the flask method, according to the regulation (EC) n°440/2008, A.6.