3-amino-N,N-dimethylpropan-1-aminium 2-C10-13-alkyl benzenesulfonate

Endpoint summary

Description of key information

Discussion of the Results for C10-C13 alkylbenzene sulfonic acid

The experiments for adsorption and desorption kinetics showed that the adsorption of the alkylbenzene sulfonic acids to the soil particles takes place slowly. The adsorption equilibrium was not reached for each analysed compound using a soil / solution ratio of 1:30. As recommended by the guideline, evaluation of phenomena which lead to the steady decrease of the test item concentration in the aqueous phase was conducted. As the results of the test item control samples measured during Tier 2 neither indicated depletion of the test item in the aqueous phase by adsorption processes on test vessels nor by degradation processes, the test item was considered to be stable in the test system over 48 h. The impact of soil parameters on the adsorption / desorption behavior of a chemical substance was considered by the selection of soils which differ significantly in their composition and physical properties. The soil type apparently does not affect the achievement of the adsorption equilibrium and the ionisation of the alkylbenzene sulfonates is not affected by the pH value in the study range from 5.0 to 7.5. To investigate the agitation time which is necessary to reach the adsorption equilibrium and to verify if an agitation time longer than 48 h (as recommended by the guideline) is applicable for the anionic compound, additional experiments have been conducted over a period of 168 h. The soil / solution ratio of 1:30 was used, as measured concentrations below the LOQ should be avoided. The results are summarized in Table 31 (detailed analytical data are not reported). Whereas the adsorption increased over time, the recovery rate for test item control samples decreased for the aqueous phase. At the same time, increasing test vessel adsorption was determined. The adsorption increased until the concentration in the aqueous phase was below the LOQ of the analytical method without showing an adsorption equilibrium in 168 h. Thus, longer agitation times than recommended by the guideline do not result in a definitive adsorption equilibrium and are therefore not applicable for this test item. A higher soil / solution of 1:5 was used to obtain the adsorption equilibrium faster and these experiments were used for evaluation of the adsorption in suspensions of some soils.

With regard to the results obtained during the experiments over 168 h, a higher soil / solution ratio of 1:5 was chosen to accelerate the adsorption process. Inappropriately, high soil / solution ratios also enhance the test item depletion in the aqueous phase with the disadvantage that the certainty in the determination of the remaining test item concentration decreases. Measured concentrations were partly below the LOQ of the analytical method. It is considered that the steady decrease of the test item in the aqueous phase is related to its chemical composition and the presence of the diamine which can work as a bridge between negative charges. To provide plausible values for Kd and KOC, data have been calculated for the best suitable soil / solution ratio (1:5 or 1:30) for each analyte regarding the degree of adsorption on the one hand and the measured concentrations on the other hand.

Summarized Endpoints - C10-C13 alkylbenzene sulfonic acid

Soil Type	Soil / solution ratio	Kd [mL/g]	KOC [mL/g]	Kdes [mL/g]	Mobility according to McCall et al.
	C10-alkylbenzene sulfonic acid
LUFA 2.2	1:5	65	4407	211	slight
LUFA 2.3	1:5	6	1462	33	low
LUFA 2.4	1:30	179	10278	194	immobile
	C11-alkylbenzene sulfonic acid
LUFA 2.2	1:5	175	11915	187	immobile
LUFA 2.3	1:5	13	3138	51	slight
LUFA 2.4	1:30	85	4862	984	slight
	C12-alkylbenzene sulfonic acid
LUFA 2.2	1:30	93	6298	939	immobile
LUFA 2.3	1:5	27	6627	79	immobile
LUFA 2.4	1:30	193	11087	1034	immobile

Summarized Endpoints - N,N-dimethyl-1,3-propanediamine

Soil Type	Soil / solution ratio	t (eq) [h]	Kd [mL/g]	KOC [mL/g]	Kdes [mL/g]	Mobility according to McCall et al.
	C10-alkylbenzene sulfonic acid
LUFA 2.2	1:100	6	143	9695	326	immobile
LUFA 2.3	1:100	24	205	49859	443	immobile
LUFA 2.4	1:100	24	515	29590	889	immobile