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Partition coefficient

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Description of key information

log Pow > 5.63

Key value for chemical safety assessment

Additional information

The log Pow of the substance Fatty acids, C16-18 and C18-unsatd., mono- (CAS 91744-09-1) was determined by QSAR calculation with KOWWIN (v1.68) for the three main components of the UVCB substance.

The substance fits into the applicability domain of the QSAR model, fragments of the test substance are part of the QSAR model training and validation dataset and therefore reliable for classification and labelling and assessment. Additionally the use of QSAR calculation for the three main components of the UVCB substance which are clearly identified but variable in concentration considers best the complex nature of UVCB substances.

For testing the substance Glycerides, C16-18 and C18-unsatd., mono- (CAS 91744-09-1) the OECD 117 (HPLC method, appropriate for log Pow 0-6) is the appropriate and preferred test method due to low water solubility of the test substance (<1 mg/L) and an expected log Pow >5.

The substance Glycerides, C16-18 and C18-unsatd., mono- (CAS 91744-09-1) is identified as follows: C16: 1-50%; C18: 1-10%; C18uns (sum): 40-100% (including oleic, linoleic and linolenic acid); monoglycerides: 80-100%; diglycerides: 0-20%. Therefore the main constituents are identified as palmitic acid glycerol monoester, stearic acid glycerol monoester and oleic acid glycerol monoester as the representative with the highest lipophilic character of the fatty acids C18-unsatd.

Since the test substance Glycerides, C16-18 and C18-unsatd., mono- (CAS 91744-09-1) is a UVCB substance with known main constituents (see three identified main constituents above) but variable concentration ranges it is more appropriate to determine the partition coefficient of its constituents than testing a single batch of the UVCB substance which depends on variable concentrations.

A test according to OECD 117 requires the use of reference substances, for the test substance with an expected log Pow >5 the reference substances number 58 (Fluoranthene, CAS 206-44-0), number 59 (Triphenylamine, CAS 603-34-9) and number 60 (DDT, CAS 50-29-3) would be appropriate. As the reference substance number 60 (DDT) is commonly not used in analytics due to toxicological reasons, the reference substance with the highest possible log Pow would be number 59 (Triphenylamine). Therefore the result of a potential test could only be log Pow = 5.1 to >5.7. The calculated results for the three main components show more precise result for assessment considering the complex nature of the UVCB substance.

The log Pow of the test substance Glycerides, C16-18 and C18-unsatd., mono- (CAS 91744-09-1) was calculated with a QSAR model for the three main constituents which fit into the applicability domain and showing precise adequate results for assessment. Therefore the result log Pow = 5.63 to 6.62 fulfills the standard information requirements for the partition coefficient n-octanol/water (section 7.8 of Annex VII of Regulation (EC) No 1907/2006).