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EC number: 293-927-7
CAS number: 91648-65-6
OECD 121/EU Method C.19: Koc > 4.27 x 10E5, logKoc > 5.63OECD 106: The higher the organic carbon content, the higher the mobility of the test substance (supporting information)
Two reliable data sources are available
regarding soil adsorption of 1,3,4-Thiadiazolidine-2,5-dithione,
reaction product with hydrogen peroxide and tert-nonanethiol. Fox (2012)
utilized the High Performance Liquid Chromatography (HPLC) according to
OECD Guideline 121 / EU Method C.19. Based on the intrinsic substance
characteristics, the HPLC method seems to be the most appropriate one.
The test substance interacts with the stationary phase of the
cyanopropyl reverse phase HPLC column containing lipophilic and polar
moieties. The dual composition of the stationary phase, having polar and
non-polar sites allows for interaction of polar and non-polar groups of
the test substance in a similar way as it is the case for organic matter
in soil or sewage sludge matrices. In particular for polar substances,
the pH has a significant influence on sorption behaviour. The test
substance, however, does not contain any relevant dissociation
constants, thus the experiment was carried out at approx. neutral pH in
a non-ionized form of the test substance. 12 reference standard
solutions, each prepared in methanol, where used (i.e. Acetanilide,
Phenol, Atrazine, Isoproturon, Triadimenol, Linuron, Naphthalene,
Endosulfan-diol, Fenthion, Phenanthrene, and DDT). Also the test
substance was diluted to 100 mL with methanol before analysis. The Koc
was determined to be > 4.27 x 10E5 with a corresponding logKoc of >
5.63. In accordance to the classification scheme of McCall et al.
(1981), the test substance is therefore considered to be environmentally
Supporting data is given by an experiment
conducted with the test substance using the batch equilibrium method
according to OECD Guideline 106 (Rocchio, 1991). Three
different soils (all silt or clay) were used with the following
characteristics: Soil 1 with 28.4 meq/100 g CEC (cation exchange
capacity), 0.82 % TOC (total organic carbon) and a pH of 7.4. Soil 2
possessed 46.2 meq/100 g CEC, 10.2 % TOC and a pH of 7.3. The last one
(Soil 3) has a CEC of 24.6 meq/100 g, 8.6 % TOC and pH of 6.4. A
preliminary adsorption test was performed using a test substance
solution at a concentration of 0.626 mg/L prior to the definitive test.
The definitive test used 5 test concentrations, 0.26, 0.60, 0.99, 1.58
and 3.04 mg/L at solution:soil ratio of 5:1 for 50 h equilibration time
to further define the adsorption coefficient. All data generated in the
definitive test were evaluated using the Freundlich equation and
adsorption isotherms were plotted. The results indicated that the
adsorption characteristics were similar among the three soil types
tested. The adsorption constants ranged from 3.89 to 20.80 (Kd: soil 1:
3.89, soil 2: 4.63, soil 3: 20.80, respectively). The adsorption
constants based upon the organic carbon content ranged from 45 to 473
(Koc: soil 1: 473, soil 2: 45, soil 3: 242, respectively). These values
indicate that the test substance is 'mobile' in the soil with the
highest organic carbon content and 'moderately mobile' in the other 2
soils which had lower organic carbon contents.
the more appropriate method used by Fox (2012),
1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen
peroxide and tert-nonanethiol is environmentally immobile with a Koc >
4.27 x 10E5 and a corresponding logKoc > 5.63. However, the supporting
information (Rocchio, 1991) indicates that the higher the organic carbon
content of the soil, the higher will be mobility of the test substance.
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