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EC number: 941-718-2 | CAS number: -
Definitive Test - Validation of the Analytical Method
The biological control samples and an analyzed analytical blank showed no significant interfering response at the retention time of the test item. The standard solutions contained a peak specific for the test item whose area changed accordingly with known concentration, hence the specificity of the method by retention time was confirmed.
The data was found to have a linear correlation within the calibration range of 0 to 265 mg/L. The R² fit of the calibration curve to the data was 0.9987, and was considered to be acceptable.
Accuracy (Recovery) and Precision
A set of recovery samples accurately fortified at a relevant concentration of test item was prepared five-fold and analyzed.
The method was considered to be sufficiently accurate and precise for the purposes of this test. The test sample results were not corrected for recovery.
Limit of Quantification (LOQ)
The limit of quantification (LOQ) was determined by calculating the sample concentration that gave a peak equivalent to ten times the baseline noise. Using this method the LOQ was determined to be 0.26 mg/L.
The study was performed to assess the ready biodegradability of the test item in an aerobic aqueous media. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No. 301F, “Ready Biodegradability; Manometric Respirometry Test” referenced as method C.4-D of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (q)).
The test item at a concentration of 100 mg/L was exposed to sewage treatment micro-organisms with mineral medium in sealed culture vessels in diffuse light at temperatures of between 23 and 24 ºC for 28 days.
The biodegradation of the test item was assessed by the measurement of daily oxygen consumption values and compound specific analyses on Days 0 to 28. Control solutions with inoculum and the reference item, aniline, together with a toxicity control were used for validation purposes.
The test item attained 73% biodegradation after 28 days and can therefore be considered to be readily biodegradable.
Chemical analysis of the 100 mg/L test preparation at 0 hours showed a mean measured concentration of 92% of nominal was obtained. A decline in measured test concentration was observed on Day 28 to less than the limit of quantification (LOQ) of the analytical method employed, which was determined to be 0.26 mg/L (100% loss over the test duration assuming 100% recovery on Day 0).
The losses observed by chemical analysis were higher than those observed by oxygen consumption. This was considered to be due to a combination of volatility of the test item and incorporation of the test item, or degradation products of the test item, into the microbial biomass. In such cases the micro-organisms present utilize carbon originating from the test item to increase their biomass by incorporation the carbon into new cells. This effectively removes the test item from the aqueous phase and hence reduces the apparent biodegradation of the test item as measured by oxygen consumption.
Chemical analysis of the abiotic test vessels on Day 0 showed a mean measured concentration of 90% of nominal was obtained with analysis on Day 28 showed a mean measured concentration of 6% of nominal was obtained. Given the low total viable counts from the abiotic test vessels on Day 28 and the low biological oxygen consumption values from these vessels it was considered that this 93% loss of test item measured by chemical analysis on Day 28 occurred due to the volatile nature of the test item.
Daily BOD values for the test substance, procedure control, toxicity control and inoculum control vessels are in Table 1. The percentage biodegradation values of the test and reference substance and toxicity controls are shown in Table 3 below. The pH results are in Table 2.
Table 3: Biodegradation values
R1, R2= Replicates 1 and 2
The mean BOD of the inoculated mineral medium (control) was 33.72 mg O2/L after 28 days and therefore satisfied the validation criterion of the test guideline.
The difference between extremes of replicate BOD values at the end of the test and at the end of the 10-day window was <20% and therefore satisfied the validation criterion of the test guideline.
The test item achieved 80% biodegradation after 28 days and is therefore considered readily biodegradable.
The toxicity control attained 67% biodegradation after 14 days and 81% biodegradation after 28 days, thereby confirming that the test item was not toxic to the sewage treatment micro-organisms used during the study.
Aniline (procedure control) attained 63% biodegradation after 14 days and 79% biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions.
Chemical analysis of the 100 mg/l test preparation at 0 hours, showed that a mean measured concentration of 97% of nominal was obtained. A decline in measured test concentration was observed at day 28 to less than the limit of quantification (LOQ) of the analytical method used which was determined to be 0.47 mg/l.
The losses observed by chemical analysis were higher that those observed by oxygen consumption, this was considered to be due to possible losses of the test substance due to its volatility during sampling and analytical procedures.
Another factor in the apparent reduced biodegradation value based on oxygen consumption values compared to losses calculated from the chemical analysis conducted may be due to incorporation of the test substance or degradation products of the test substance into the microbial biomass. In such cases, the micro-organisms present utilise carbon originating from the test substance to increase their biomass by incorporating the carbon into new cells. This effectively removes the test substance from the aqueous phase and hence reduces the apparent biodegradation of the test item by oxygen consumption.
The test substance biodegraded to an extent of 80% after 28 days. The data support characterizing the test substance as readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criterium is not applied to multi-component substances when assessing their ready biodegradability.
Hydrocarbons, C9-C11, n-alkanes, isoalkanes, <2% aromatics is considered readily biodegradable based on read-across from structural analouges
No measured biodegradation data are available for the registration substance itself. However, reliable data are available for related substances in the relevant carbon number range, including a study on two similar Fischer-Tropsch process-derived material (GTL Solvent GS160 and GTL Solvent GS170).
In an OECD 301F manometric respirometry test conducted in compliance with GLP, Hydrocarbons, C9-C12, n-alkanes, isoalkanes, <2% aromatics (GTL Solvent GS170) attained 80% degradation in 28 days (Vryenhoef, 2014a). The 10-day window criterion is not applicable for complex substances where sequential degradation of the constituents takes place ( REACH guidance R.7b ECHA, 2017). The substance was therefore concluded to be readily biodegradable.
Hydrocarbons, C8-C11, n-alkanes, isoalkanes, <2% aromatics (GTL Solvent GS160) has been tested in an OECD 301F (manometric respirometry) test conducted in compliance with GLP (Best, 2014). The test substance attained 73% biodegradation in 28 days and was therefore considered to be readily biodegradable.
These studies are considered to be reliable and are used as weight of evidence that Hydrocarbons, C9-C11, n-alkanes, isoalkanes, <2% aromatics is readily biodegradable.
In a supporting study, Hydrocarbons, C9-C11, n-alkanes, isoalkanes, cyclics, <2% aromatics, biodegraded 80% after 28 days under the conditions of the study and is readily biodegradable.
The available data cover the entire carbon number range relevant to the registration substance and the test materials contain similar chemical structures. The results are therefore read across to Hydrocarbons, C9-C11, n-alkanes, isoalkanes, <2% aromatics. Both tested substances demonstrated significant biodegradation and it can therefore be concluded that the registration substance is readily biodegradable.
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