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EC number: 242-745-6
CAS number: 19009-56-4
Immobilization Rates after 24 and 48 hours of Exposure in the Definitive
(n = 20, divided into 4 replicates with 5 daphnids each)
Measured Concentrations of the Transformation Product calculated
as2-Methyldecan-1-alduring the Definitive Test
Meas. conc = measured concentration of the
transformation product 2-Methyldecanoic acid, dilution factor taken into
Calc. conc. = equivalent concentration
of2‑Methyldecan-1-alcalculated from the measured concentration of the transformation
product (conversion factor: 0.914, based on the ratio of molar weights
of 2‑Methyldecan‑1‑al: 2-Methyldecanoic
acid, 170.3 g/mol : 186.3 g/mol)
% = percentage of the nominal concentration of the
LOQMetabolite = limit of quantification of the
analytical method for the transformation product 2-methyldecanoic acid (0.3
mg 2-methyldecanoic acid/L)
LOQTest item = limit of quantification of the analytical method for the
test item (0.1 mg test item/L)
Water Quality Parameters at the Start of the Exposure (0 hours)
(measured in one additional replicate (without daphnids) per
concentration level and control)
Water Quality Parameters at the End of the Exposure (48 hours)
(measured in one replicate per concentration level containing daphnids)
Water Quality Parameters of the Dilution Waterat the Start of the
Exposure (0 hours)
O2 concentration [mg/L]
In the acute immobilization test with Daphnia magna (STRAUS), the
effects of the test item were determined at the test facility according
to OECD 202 (2004).
The study was conducted in a closed system (sealed glass flasks) without
headspace under static conditions over a period of 48 hours with a
saturated solution prepared with a nominal loading of 100 mg/L of the
test item and 4 subsequent dilution levels in a geometric series with a
separation factor of 2.2. The nominal concentrations of the test item
were: 4.27 – 9.39 – 20.7 – 45.5 – 100 mg/L.
All concentration levels were visually clear throughout the exposure
period. No Tyndall effect was observed in the saturated solution before
insertion of the daphnids.
Twenty daphnids (divided into 4 replicates with 5 daphnids each) were
exposed to each concentration level and the control.
The concentrations of the test item were analytically verified via
LC-MS/MS in the fresh media at the start of the exposure (0 hours),
after 24 hours and in the 48 hours old media at the end of the exposure
in all concentration levels and the control.
The measured concentrations of the test item after derivatization were <
LOQ of the nominal values at the start of the exposure (0 hours), after
24 hours of exposure and at the end of the exposure (48 hours).
Therefore, the concentrations of the transformation product
2-methyldecanoic acid were analyzed and calculated as 2‑Methyldecan‑1‑al
concentrations by conversion with a factor of 0.914 (based on the ratio
of the molar weights of the test item and its transformation product).
The time weighted average concentrations of the test item were
calculated based on these concentrations to be: 1.56 – 3.68 – 8.11 –
21.3 – 47.5 mg/L.
Additionally, all concentration levels and the control were analytically
verified via analysis of total organic carbon (TOC, according to DIN EN
1484) at the start of the exposure (0 hours), after 24 hours of exposure
and the end of the exposure (48 hours).
All effect concentrations are based on the time weighted average
concentrations of the test item 2-Methyldecan-1-al. Additionally, the
effect concentrations are given based on the nominal test item
The validity criteria of the test guideline were fulfilled.
Based on the time weighted average concentrations of the test item
2-Methyldecan-1-al, the 48 hours-EC50 for Daphnia magna was 31.8 mg/L
(with confidence limits: 21.3 – 47.5 mg/L).
Based on the nominal concentrations of the test item 2-Methyldecan-1-al,
the 48 hours-EC50 for Daphnia magna was 67.5 mg/L (with confidence
limits: 45.5 – 100 mg/L).
48h EC50 (Daphnia magna) = 31.8 mg/L (meas.), OECD 202; Anon., 2017
In a single key study, the effects of the test item to Daphnia magna
were determined at the test facility according to OECD 202 (2004).
To account for degradation of the parent substance aldehyde to acid or
further degradation products, preliminary testing was conducted to
assess the stability of the test item under test conditions. After 24
hours of slow stirring, followed by a 1 hour settlement phase, all
measured concentrations via LC-MS/MS of test item were below LOQ. A
second stability assessment was conducted with analysis of the test item
(parent) and the corresponding transformation product (2 -methyldecanoic
acid) using a saturated solution with a nominal concentration of 100
mg/L. Slow stirring was applied to the test solution. Analytical samples
were taken at 0, 24, 48 and 72 hours after initiation of stirring.
Measured concentrations of the parent substance were <LOQ at all time
points. The highest concentration of transformation product was found
after 72 hours of stirring. The measured amount of transformation
product was calculated as the corresponding amount of parent. This
preliminary work was used to design the medium preparation method for
this study. In accordance with OECD Series on Testing and Assessment No.
23 (2000), when chemical substances have a very short half-life, it is
more relevant to assess the toxicity of the major transformation
product(s) as the toxicity of this entity is more relevant for actual
environmental exposure. Therefore, the acute toxicity testing on aquatic
invertebrates is based on the measured amount of transformation product
expressed as the corresponding amount of parent.
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