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Adsorption / desorption

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Description of key information

The adsorption of 3,5-Dimethylpyrazole was determined to be Koc 1.2 x 10^5 and log Koc 5.1, in a key study (Baltussen, 2012) which was performed in line with GLP and the standardised guidelines OECD 121 and EU Method C.19.

Key value for chemical safety assessment

Koc at 20 °C:
120 000

Additional information

The adsorption of the test material was determined in a GLP compliant study (Baltussen, 2012) performed in accordance with standardised guidelines, with a sufficient level of detail to assess the quality of the presented data. The study was performed to a good standard and was assigned a reliability score of 1 in accordance with Klimisch (1997).

Based on pKa calculations the HPLC analysis was performed at a neutral pH. Solutions of reference substances with known log Koc values based on soil adsorption data and the test substance were analysed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the references substances were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. The coefficient of correlation (r) was calculated. The log Koc value for the test substance was calculated by substituting its mean log k’ in the calibration curve. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.

Under the conditions of the test, the Koc and log Koc of the test material were determined to be 1.2 x 105and 5.1, respectively. This large adsorption coefficient value demonstrates very little to no mobility through the soil of the chemical.

The adsorption profile of the substance has been sufficiently characterised in the screening test and further testing would not improve the risk assessment of the substance.

[LogKoc: 5.1]