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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 24 January to 25 February 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Deviations:
yes
Remarks:
see § Overall remarks
GLP compliance:
yes (incl. QA statement)
Type of method:
shake-flask method to: flask method
Remarks:
At pH = 2
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
- Name of test material (as cited in study report): Calcium tartrate
- Physical state: amber powder
- Analytical purity: 93.44%
- Lot/batch No.: Camp 09.10
- Expiration date of the lot/batch: December 2011
- Storage conditions of test material: at room temperature, protected from light and humidity.
Analytical method:
gas chromatography
Type:
log Pow
Partition coefficient:
-1.46
Temp.:
20 °C
pH:
2
Remarks on result:
other: or -1.85 (shake flask method)
Type:
log Pow
Partition coefficient:
-3.6
Temp.:
20 °C
pH:
7
Remarks on result:
other: estimated value
Type:
log Pow
Partition coefficient:
-3.7
Temp.:
20 °C
pH:
9
Remarks on result:
other: estimated value
Details on results:
OCTANOL/WATER PARTITION COEFFICIENT (EEC A8)
Measured value at pH < 2
In a first experiment, a 100 mL aliquot of a 120.0 mg/L stock solution of the test item in water (based on Calcium tartrate tetrahydrate) was set
at pH 1.9 with HCl 37%.
The verification of the acidified stock solution gave 109.5 mg/L as the measured value (five replicate determinations), and thus represented 91.4%
only of the nominal value. The un-acidified solution was checked to be within 2% of the nominal value (duplicate determinations). The reason why
acidification of the aqueous test item stock solution resulted in lower content for Calcium tartrate is not known.
The determination was attempted using duplicate 20 mL volumes of pre-saturated octanol and 2 mL of the acidified aqueous test item stock solution.
The test was reproduced using half and twice, respectively, the above volume ratio and replicate determinations: 30 mL octanol + 1.5 mL of acidified
aqueous solution and 20 mL octanol + 4 mL of acidified aqueous solution.
The tubes were continuously rotated for 15 min and then centrifuged for 10 min at 3500 tr/min and 20°C.
The pH of the water phase was measured as 1.95 at the end of test.
Recovery of Calcium tartrate in the aqueous phase ranged between 67.6 and 85.3% of the nominal added amount, based on the nominal value for the aqueous test item stock solution, suggesting that Calcium tartrate in the octanol phases was not negligible.
Unfortunately the IC determination of Calcium tartrate in the octanol phase was not feasible: successive injections showed that octanol had
detrimental effects on the IC column, resulting in high pressure, false peaks and non-reproducible results. Dilution of the octanol phase was
attempted in methanol or ethanol, but here also the signal was considered as abnormal.
Indirect calculations were applied for the determination of Calcium tartrate in the octanol phases:
- Amount, mg, in octanol = (total amount, mg) – (amount, mg, in water)
- Concentration in octanol = 1000 x (Amount, mg, in octanol)/(Volume, mL, of octanol)
Consequently, the octanol/water partition coefficient values depended on whether the nominal value or the measured value was taken into account
for the determination of the total added amount in the two-phase system. In both cases the validity criteria were fulfilled: The six Log Pow values fell
within a range of ± 0.3 units.
When based on the nominal value, 120 mg/L Calcium tartrate, for the aqueous test item stock solution:
Mean Log Pow = -1.55 Observed interval = -1.62; -1.45
When based on the measured value, 110 mg/L Calcium tartrate, for the aqueous test item stock solution:
Mean Log Pow = -1.80 Observed interval = -1.85; -1.76
Conclusions:
At pH = 2 Log Pow = -1.46 or -1.85 (Shake flask method)
At pH = 7, Log Pow = -3.6 (estimated value)
At pH = 9, Log Pow = -3.7 (estimated value)
Executive summary:

The measurement of the octanol/water coefficient was difficult to achieve.

At pH < 2, recovery of Calcium tartrate in the water phase was not total, suggesting that Calcium tartrate in the octanol phase was not negligible. Unfortunately the developed IC method for the quantification of Calcium tartrate in water was proved not to be convenient for the octanol phase.

The amount of Calcium tartrate in the octanol phase was calculated on the basis of total added amount minus measured amount in the water phase, while postulating that recovery of Calcium tartrate in the two-phase system should be total.

Depending on whether thenominal added amount or the measured added amount was taken into account, the mean value for Log Pow was calculated as -1.46 or -1.85.

At both pH = 7 and pH = 9 recovery of Calcium tartrate in the water phase was almost total, and the conclusion was that the quantification of Calcium tartrate in the octanol phase was not feasible.

The octanol/water partition coefficient was estimated on the basis of the ratio of the solubility of Calcium tartrate in each octanol and in water at the required pH value.

Log Pow at pH 7 = -3.6

Log Pow at pH 9 = -3.7

Description of key information

The measurement of the octanol/water coefficient was difficult to achieve.

At pH < 2, recovery of Calcium tartrate in the water phase was not total, suggesting that Calcium tartrate in the octanol phase was not negligible. Unfortunately the developed IC method for the quantification of Calcium tartrate in water was proved not to be convenient for the octanol phase.

The amount of Calcium tartrate in the octanol phase was calculated on the basis of total added amount minus measured amount in the water phase, while postulating that recovery of Calcium tartrate in the two-phase system should be total.

Depending on whether thenominal added amount or the measured added amount was taken into account, the mean value for Log Pow was calculated as -1.46 or -1.85.

At both pH = 7 and pH = 9 recovery of Calcium tartrate in the water phase was almost total, and the conclusion was that the quantification of Calcium tartrate in the octanol phase was not feasible.

The octanol/water partition coefficient was estimated on the basis of the ratio of the solubility of Calcium tartrate in each octanol and in water at the required pH value.

Log Pow at pH 7 = -3.6

Log Pow at pH 9 = -3.7

Key value for chemical safety assessment

Log Kow (Log Pow):
-3.6
at the temperature of:
20 °C

Additional information