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EC number: 239-556-6 | CAS number: 15520-10-2
Partition coefficient
Administrative data
Link to relevant study record(s)
- Endpoint:
- partition coefficient
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 17 Nov - 14 Dec 1989
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Guideline study (EPA Guidelines 40 CFR 796.1550).
- Qualifier:
- according to guideline
- Guideline:
- other: EPA Guidelines 40 CFR 796.1550
- Principles of method if other than guideline:
- MPMD was partitioned between n-octanol and water at 25 °C and at pH values of 5.0, 7.0, and 9.0. The phases were separated and analysed for MPMD using gas chromatographic (GC) analysis.
- GLP compliance:
- yes
- Type of method:
- estimation method (solubility ratio)
- Partition coefficient type:
- octanol-water
- Analytical method:
- gas chromatography
- Type:
- Pow
- Partition coefficient:
- <= 7.9
- Temp.:
- 25 °C
- pH:
- 9
- Remarks on result:
- other: corrected for ionisation.
- Type:
- log Pow
- Partition coefficient:
- <= 1
- Temp.:
- 25 °C
- pH:
- 9
- Remarks on result:
- other: corrected for ionisation.
- Details on results:
- See below.
- Conclusions:
- The log Pow of the test substance is below 1 at pH 9 and 25 °C.
- Executive summary:
The partition coefficient was determined according to EPA Guidelines 40 CFR 796.1550.
The test substance MPMD was partitioned between n-octanol and water at 25 °C and at pH values of 5.0, 7.0, and 9.0. The phases were separated and analysed for MPMD using gas chromatographic (GC) analysis. Actually, no MPMD was found in the octanol phases. Therefore, the partition coefficient was calculated for pH=9 using the detection limit as worst-case-concentration of MPMD in n-octanol. The yielded partition coefficient value was then corrected for ionisation by calculation using literature data of the pka values.
The log Pow of the test substance is below 1 at pH 9 and 25 °C.
Reference
Chromatography
Under the conditions used in this study, MPMD eluted with a retention time of 0.7-0.9 minutes. Analytical precision was approximately 0.6% (standard error of the mean). Typical calibration curve R2 values were >0.995. The detection limit was <0.01 mM.
Partitioning
Under the conditions employed in this study, MPMD partitioned exclusively into the aqueous phase. Concentrations in the aqueous phase after equilibration were approximately 2.0 mM (high concentration) and 0.20 mM (low concentration). The total recovery of MPMD (for replicate determinations) ranged from 79 to 119% nominal (high concentration) and 90 to 120% nominal (low concentration).
Kow Estimation
Since MPMD could not be detected in the n-octanol phase at either the initial test concentrations or at any pH, a Kow value was calculated assuming the concentration in the n-octanol phase was equal to the detection limit (worst-case situation). Using pKa values for MPMD of 10.0 and 11.2 from literature (Reference 1: Conoco Analytical Report # 711539, 1987), the n-octanol/water partition coefficient of MPMD at pH 9.0 was corrected for ionisation.
Uncorrected:
Kow =/< (0.01 mM/2.0 mM)
Kow =/< 0.005
Corrected:
Kow (corr) = Kow * exp ((pKa1 - pH) + (pKa2 - pH)
Kow (corr) =/< 7.9
Due to the detection limits of this partitioning study, Kow values were not calculated at the other pH values or at the lower concentration. Partitioning of MPMD into the n-octanol phase would theoretically be 100 and 10000 times less at pH values of 7.0 and 5.0, respectively.
Description of key information
The log Pow of the test substance is below 1 at pH 9 and 25 °C.
Key value for chemical safety assessment
- Log Kow (Log Pow):
- 1
- at the temperature of:
- 25 °C
Additional information
The partition coefficient was determined according to EPA Guidelines 40 CFR 796.1550.
The test substance MPMD was partitioned between n-octanol and water at 25 °C and at pH values of 5.0, 7.0, and 9.0. The phases were separated and analysed for MPMD using gas chromatographic (GC) analysis. Actually, no MPMD was found in the octanol phases. Therefore, the partition coefficient was calculated for pH=9 using the detection limit as worst-case-concentration of MPMD in n-octanol. The yielded partition coefficient value was then corrected for ionisation by calculation using literature data of the pka values.
The log Pow of the test substance is below 1 at pH 9 and 25 °C.
A conservative log Pow value of 1 is taken for safety assessment purposes.
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