Distillation residue, butyl alcohols production, rectification

Partition coefficient

Description of key information

This study was conducted according to the method EC 440/2008. The study was performed by using HPLC with Zorbax Hypersil BDS C18-column. Test substance is a UVCB-substance which is a by-product of butyl alcohol production by propylene oxosynthesis manufactured at petrochemical industry. It is a mixture of several organic substances, and only one constituent in the mixture can be analytically identified and quantified (2-ethylhexanol). The typical portion of this known constituent in the mixture is between 20-30 % . Because the other components were not identifiable, the octanol-partition coefficient study was conducted for the mixture rather than determining this property for the substance only based on the partition coefficient of one known constituent of the mixture. The HPLC method was chosen because it is also recommended for complex mixtures i.e. petroleum products which are comparable with the test substance.

Additional information

Test substance is a UVCB-substance which is a by-product of butyl alcohol production by propylene oxosynthesis manufactured at petrochemical industry. It is a mixture of several organic substances, and only one constituent in the mixture can be analytically identified and quantified (2-ethylhexanol). Therefore, the octanol-partition coefficient study was conducted for the mixture rather than determining this property for the substance only based on the partition coefficient of one known constituent of the mixture.

The HPLC method was chosen because it is also recommended for complex mixtures i.e. petroleum products which are comparable with the test substance. The study was conducted according to the method EC 440/2008 using the HPLC method. The HPLC used for this study was an Agilent 1100 series equipped with a diode array detector. The Zorbax Hypersil BDS - C18 column was used with 3:1 methanol water as an eluent.

According to the study results, the calibration gave a linear trend with an r² value of 0.901. The test substance, being a mixture of several substances gave an abundance of peaks in the UV Chromatogram, with a cluster of peaks between retention time of 2.2. and 6.4 minutes corresponding to log Kow values of 1.8 to 5.8 and several peaks scatted throughout the chromatogram the last being registered at 25.9 min corresponding to a log Kow value of 6.4. In addition, there was a strong signal detected on the UV detector when column was washed with 100 % methanol after the 60 min run, the compounds responsible for this signal have log Kow values considerably exceeding 7.5. An ESI MS detector was also tested but only gave ionization for the compounds eluted at 100 % methanol. Due to the lack of a suitable general detector it can not be said which compounds are major compounds of the mixture and which are only minor ones.

As a conclusion of the experimental data, the log Kow of the test substance varies between 1.8 to 7.5. This indicates that the test substance might also contain constituents having potential for bioaccumulation (log Kow > 3). Due to the lack of a suitable general detector it was impossible to determine which were the major compounds of the mixture and which were only minor ones.

Test substance is a mixture of several constituents having different physicochemical properties. However, the composition is not easily identifiable and therefore the Kow values are considered as tentative values of the test substance.