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Physical & Chemical properties

Water solubility

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Reference
Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7840 (Water Solubility)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 830.7860 (Water Solubility Generator Column Method)
Qualifier:
according to guideline
Guideline:
OECD Guideline 105 (Water Solubility)
GLP compliance:
yes (incl. QA statement)
Remarks:
Exception: The characterization and stability of the test substance under storage conditions at the test site were not determined in accordance with GLP Standards.
Type of method:
column elution method
Remarks:
modified by use of a generator column apparatus
Specific details on test material used for the study:
The substance name 3.5 G FF is one of the commenrcial names for p-t-butylphenyldiphenyl phosphate and bis(p-t-butylphenyl) phenyl phosphate
Key result
Water solubility:
109 µg/L
Conc. based on:
test mat. (dissolved fraction)
Temp.:
20 °C
Remarks on result:
other: based on the primary component (C4)
Conclusions:
Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
The water solubility of the test substance in reagent water at 20°C was determined using the column elution method. Column elution water was diluted with an equal amount of acetonitrile and analyzed for test substance concentrations using TPP, C4, C8 and C12 mixture components as a proxy of the test substance solubility using high performance liquid chromatography with ultraviolet detection (HPLC/UV). The mean water solubility for 3.5 G FF, based on the primary component C4, at 20.0 ± 0.1 °C was 109 ± 14 μg/L (CV=13%, N=10).
Executive summary:

Under the experimental conditions presented, the mean measured reagent water solubility for

3.5 G FF, a mixture, was a function of the component selected as a proxy for the test substance. Based on

mixture components TPP, C4, C8, and C12, the water solubility of 3.5 G FF at 20ºC was measured as

8059 ± 90.8 μg/L (CV = 1.1%, N = 8), 99.5 ± 14 μg/L (CV = 14%, N = 5), < 20.0 μg/L (N = 8), or

< 500 μg/L (N = 8), respectively, at a column elution flow rate of 1.0 mL/min. Based on these same

mixture components, the solubility of 3.5 G FF was measured as 8038 ± 59 μg/L (CV = 0.73%, N = 8),

118 ± 5.2 μg/L (CV = 4.4%, N = 5), < 20.0 μg/L (N = 8), or < 500 μg/L (N = 8), respectively, at the

confirmatory column elution flow rate of 0.5 mL/min. The mean measured 3.5 G FF concentrations as a function of column elution flow rate using TPP and C4 to monitor the test substance differed by 0.25% and 17%, respectively, which were within the ± 30% percent difference test criterion.

The overall mean measured water solubility of 3.5 G FF based on mixture components TPP, C4, C8, and

C12 was 8048 ± 75 μg/L (CV = 0.93%, N = 16), 109 ± 14 μg/L (CV = 13%, N = 10), < 20.0 μg/L (N =

16), or < 500 μg/L (N = 16), respectively. The pH was measured for an aqueous sample collected at a flow rate of 1.0 mL/min. The measured pH of the

reagent water used in the study was 6.3, while the measured pH of an aqueous sample collected at a flow

rate of 1.0 mL/min was 7.4.

During the HPLC/UV analysis, an unknown polar compound with high solubility was seen. To confirm the identity of the unknown peak, a

post-spiked column elution sample was prepared from one of the original confirmation column elution

samples (238C-126-4). Based on correspondence with the Sponsor, 4-tert-butylphenol (p-t-BP) was

suggested to identify the unknown peak on a retention time match basis. According to the Sponsor, p-t-BP is used as a starting material in the production of the test substance. Some p-t-BP remains in the

product following production as an impurity at a level that ranges between 1000 to 1500 ppm.

The compound was ordered from Aldrich and a 100 mg/L solution was prepared in ACN. The

resulting stock solution was used to post-spike an aliquot of the cited sample. A slight shift in component retention times may be noticed relative to the confirmation

sequence due to different analyses on different dates. The post-spike sample was run on the HPLC/UV

under the same operating conditions as was used for 3.5 G FF and was found to have an identical

retention time to that of the unknown peak. As for TPP, p-t-BP is a relatively water soluble

component extracted from the product into the column elution water. We estimated that the concentration

of p-t-BP reached approximately 600 mg/L in the water samples although it is present in only a trace

amount in the product.

At the Sponsor’s request, additional method development was performed on water solubility

samples and p-t-BP standards. The pH of an aliquot of a p-t-BP standard and 3.5 G FF water solubility

sample were adjusted to a pH of ~12 and a pH of ~14 using 1M sodium hydroxide (NaOH). The

documented pKa of p-t-BP is 10.16 at 25°C (5). The pH adjusted standards and water solubility samples

were analyzed by HPLC/UV along with aliquots of the same p-t-BP standards and water solubility

samples under their unadjusted pH (~7.4 for water solubility sample). Representative chromatograms of a

p-t-BP standard under unadjusted pH and at pH ~12 and 3.5 G FF water solubility sample under

unadjusted pH and at pH of ~14 are presented in Figure 9. Under extremely basic conditions (i.e. pH ~12

and pH ~14), p-t-BP in the pH adjusted standards and water solubility samples exhibited an increasing

shift to shorter retention times with increasing pH. The peak areas for TPP and C4 decreased under more

basic conditions, while the peak area of p-t-BP remained relatively unchanged between the unadjusted pH

and more basic samples. This increasing shift to shorter retention times with increasing pH may possibly

indicate that a shift in equilibrium from the non-dissociated form of p-t-BP to a more polar dissociated

form of p-t-BP has occurred.

Description of key information

Key value for chemical safety assessment

Water solubility:
109 µg/L
at the temperature of:
20 °C

Additional information