Sulfuric acid, mono-C14-16 (even numbered)-alkyl esters, sodium salts

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Recalculation based on the available experimental data for read-across substances.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Experimental data for pure homologues: C8, C10, C12 and C14 AS homologues with sediment from artificial pond (organic carbon content 22%). Determination of alkyl sulfates using methylene blue assay. Recalculation was made for C16, C18 and C20 AS.

GLP compliance:

no

Type of method:

other: recalculation based on experimental data for read-across substances

Media:

sediment

Type:

log Koc

Value:

3.515 dimensionless

Temp.:

25 °C

% Org. carbon:

22

No experimental data on adsorption coefficient of C16AS Na (CAS 1120-01-0) are available. Nevertheless, the experimental values of adsorption coefficient are presented in the publication of Marchesi et al. (1991) for pure AS homologues: C8 (CAS 142-31-4), C10 (CAS 142-87-0), C12 (CAS 151-21-3) and C14 (CAS 1191-50-0). The determined Koc values are:

- for C8 homologue (CAS 142-31-4) between 75 and 100 which corresponds to log Koc values in the range of 1.88 and 2.0

- for C10 homologue (CAS 142-87-0) between 122 and 178 which corresponds to log Koc values in the range of 2.09 and 2.25

- for C12 homologue (CAS 151-21-3) between 316 and 446 which corresponds to log Koc values in the range of 2.5 and 2.65

- for C14 homologue (CAS 1191-50-0) between 1337 and 1567 which corresponds to log Koc values in the range of 3.13 and 3.19

Adsorption coefficient for pure homologues C16 AS (CAS 1120-01-0) was extrapolated based on the above experimental data. The log Koc values were taken from the regression line constructed based on C8 – C14 data: y = 0.1985x + 0.339 (R2=0.974 proving a very good fit).

The results show that log Koc for C16 homologue equals 3.515.

The extrapolation based on experimental data was chosen as the most reliable method of determining Koc value for the C16 homologue. Other calculation methods of adsorption coefficient e.g. EPISUITE are not reliable. According to OECD SIDS Initial Assessment Report for Alkyl Sulfates (2007) when comparing EPISUITE calculations and experimental derived Koc, the calculated values are significantly higher. This happens because surfactancy and dissociation are not taken into account in the EPI Suite estimations. Therefore the calculated Koc value should not be used for the exposure assessment since they are not reliable.

Thefore, the reliable log Koc of C16AS Na (CAS 1120-01-1) is 3.515 which equals to Koc value of 3273.

Reference 2

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Sorption experiments with sediment from artificial pond (organic carbon content 22%). Determination of alkyl sulfates using methylene blue assay.

GLP compliance:

no

Type of method:

HPLC estimation method

Media:

sediment

Radiolabelling:

no

Test temperature:

25 °C

Details on study design: HPLC method:

IDENTIFICATION AND QUANTIFICATION OF TEST SUBSTANCE/PRODUCT
- Separation method (e.g. HPLC, GC): Gas chromatography (Perkin-Elmer-F33-Chromatograph with FID)
- Conditions (column, mobile phase, etc.): Glass column (1.5 m x 5 mm), packed with 15% (w/w) ethylene glycol succinate silicone (EGSS-X) on 80-100 mesh Chromosorb
- Detection method (e.g. ECD, UV, MS, ICP-AES, ICP-MS): Injector and detector temperatures 225 °C, carrier gas N2 at a pressure of 280 kN/m2

Analytical monitoring:

yes

Details on matrix:

- Details on collection (e.g. location, depth, contamination history, procedure: obtained from artificial pond through which part of a stream at the Institute of Freshwater Ecology, River Laboratory site may be directed, collection on 20 Nov 1988 and 23 March 1989; using fine mesh sieve (2 mm), dried at 85 °C and passed successively through sieves of 2, 0.319 and 0.125 mm size, organic carbon removed, then treatment of 250 g sediment with 500 mL 0.1M NaOH for 24 hours, filtration of supernatant and subsequent acidification with concentrated HCl to final pH of 1.5
- Textural classification (i.e. %sand/silt/clay): clay, particles <0.125 mm, humic fraction used
- Organic carbon (%): 22.2% by weight, however removed by pretreatment with hydrogen peroxide, resulting in humic fraction
- Specific surface area: 8.24 m2/g with BET c constant of 56.0
- Mineral composition: quartz and calcite, some feldspars and mica

Details on test conditions:

TEST SYSTEM
- Type, size and further details on reaction vessel: Adsorption apparatus: solution in contact with suspended adsorbent was circulated via syringe pump (through 0.1 µm cellulose nitrate filter) via valve K, operated by stepper motor, PTFE tubing was flushed thoroughly before sample was directed to fraction collector J; 200 mL 10 mM NaHCO3 was weighed into the adsorption cell and allowed to come to thermal equilibrium with CO2/N2 mixture to give a pH of 7.6 ± 0.02; Adsorbent was added to the cell and left for 1 h before a sample was removed for analysis; stock solution of AS added from autoburette and after 20 min a sample was removed for analysis; Procedure was repeated with successive additions of AS. Isotherm computed from data retrieved from the autoburette and the surfactant.

Type:

Koc

Value:

> 1 337 - < 1 567 dimensionless

Temp.:

25 °C

Type:

log Koc

Value:

> 3.13 - < 3.19 dimensionless

Temp.:

25 °C

Reference 3

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

Summary of available data used for the endpoint assessment of the target substance

Adequacy of study:

key study

Justification for type of information:

Refer to the Category Approach Justification document provided in IUCLID6 Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Type:

log Koc

Value:

> 3.13 - < 3.19 dimensionless

Temp.:

25 °C

Remarks on result:

other: Source: CAS 1191-50-0, Marchesi, 1991

Type:

log Koc

Value:

3.515 dimensionless

Remarks on result:

other: Source: CAS 1120-01-0, AS Consortium, 2012

Description of key information

log Koc between 3.13 and 3.515

Key value for chemical safety assessment

Koc at 20 °C:

1 337

Additional information

Since no reliable adsorption tests are available for C14-16AS Na (CAS 91648-54-3), in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to another structurally related category members was conducted. Read-across data available for the pure AS homologues: C14AS Na (CAS 1191-50-0) and C16AS Na (CAS 1120-01-0). In the publication by Marchesi et al. (1991), the experimental sediment sorption data for several alkyl sulfates with different carbon chain lengths are presented. The Koc values for the longer homologue C16AS Na (CAS 1120-01-0) was extrapolated from the available data on C8-14 alkyl sulfates.

The determined Koc values are:

- for C14AS Na (CAS 1191-50-0) between 1337 and 1567 which corresponds to log Koc values in the range of 3.13 and 3.19.

- for C16AS Na (CAS 1120-01-0) the extrapolated value of Koc equals 3273 which corresponds to log Koc 3.515.

Due to structural and property similarities with the tested category members these results apply also to C14-16AS Na (CAS 91648-54-3). The Koc range is between 1337 and 3273 corresponding to the log Koc range between 3.13 and 3.515. Adsorption of the substance to soil or sediment is therefore assumed to be low to moderate. For the PNEC sediment and soil derivation according to the equilibrium partitioning method (EPM), the lower boundary of the range (Koc = 1337) was taken into account, since this value represents the worst case scenario for the chemical safety assessment.

[LogKoc: 3.13]