Lecithins, acetylated

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Qualifier:

according to guideline

Guideline:

EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Test temperature:

20-25 ºC

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: HPLC
- Type: Agilent Series 1100/1200 High Performance Liquid Chromatograph (HPLC)
- Type, material and dimension of analytical (guard) column: Zorbax CN (150 mm x 4.6 mm, 5-μm particle size)
- Detection system: Agilent Series 1100 Variable Wavelength (UV) Detector and an Alltech 500 Evaporative Light Scattering Detector (ELSD)

Test substance solutions were prepared by direct weight in 10.0 millilitres of 80% hexane: 20% isopropyl alcohol (IPA) (v/v). An appropriate amount of six reference substance stocks of known Log KOC were fortified into two 10.0-millilitre volumetric flasks preloaded with 4.5 millilitres of HPLC-grade bottled water (H2O) and brought to a 10.0-millilitre final volume with methanol (MeOH). The combined reference standard solutions yielded a final solution composition of 55% MeOH: 45% H2O (v/v). The combined reference standard and test substance solutions were sequentially injected into an HPLC system. The HPLC system was operating standardized isocratic, reverse-phase operating conditions until after the elution of the reference standards. Following the elution of the last reference standard, DDT, a gradient was employed in order to elute the test substance off from the cyanopropyl-based stationary phase. Capacity factors were calculated for the reference standards using thiourea to estimate column dead time (i.e. the retention time of an unretained organic compound). The logarithms of the capacity factors were then plotted against published log KOC values to establish a linear regression equation. Because the test substance required a different operating condition, the Log KOC of all the components that eluted as a result of the gradient were reported as a greater than value.

All solvents and reagents were ACS reagent-grade or better.
Reagent Water: HPLC-Grade, Burdick & Jackson, Lot No. DA019 (equivalent to ASTM Type II Designation D1193-06 (3)).
Methanol (MeOH): HPLC-Grade, Burdick & Jackson, Lot Nos. CZ918 and DA170.
Acetonitrile (ACN): HPLC-Grade, Burdick & Jackson, Lot No. CZ448.
Hexane: HPLC-Grade, Burdick & Jackson, Lot No. CY891.
Isopropyl Alcohol (IPA): HPLC-Grade, Burdick & Jackson, Lot No. CY545.

MOBILE PHASES
- Type: HPLC
- Experiments with additives carried out on separate columns: no
- pH: 6-7
- Solutes for dissolving test and reference substances: The initial HPLC mobile phase composition was 55% MeOH: 45% H2O (v/v). Following the elution of the last reference standard DDT, the mobile phase composition was ramped to 90% MeOH: 10% H2O (v/v) by way of a gradient in order to elute any remaining test material off the column. The mobile phase composition was then ramped back down to the 55:45 MeOH:H2O (v/v) starting composition prior to the next injection. The various mobile phase compositions were prepared in situ by the HPLC system from reservoirs containing MeOH and H2O. The mobile phase components were degassed by the instrument prior to use. An aliquot of the eluent leaving the analytical column was collected and the pH was measured using pH indicator paper.

DETERMINATION OF DEAD TIME
- Method: Capacity factors were calculated for the reference standards using thiourea to estimate column dead time (i.e. the retention time of an unretained organic compound).

REFERENCE SUBSTANCES
- Identity: Two combined reference standards consisting of a total of six reference substances were prepared and analyzed. One reference substance, thiourea, was prepared and analyzed to determine the analytical column dead time. In conjunction with thiourea, the remaining five reference substances in the combined standards were used to prepare a calibration curve. The six reference substances are identified. 1) Thiourea was received from Sigma-Aldrich on September 24, 2009, and was assigned Wildlife International, Ltd. identification number 9200 upon receipt. The reference standard, a solid, was identified as: Thiourea, ACS Reagent; lot number 1428866, CAS number 62-56-6, with an assigned expiration date of September 30, 2015. The reference standard had a reported purity of 99.7%, and was stored in darkness under ambient conditions, 2) Acetanilide was received from Sigma-Aldrich on August 14, 2006 and was assigned Wildlife International, Ltd. identification number 7693 upon receipt. The reference standard, a solid, was identified as: Acetanilide, reagent grade, 97%; lot number 20501TC, CAS number 103-84-4, with an assigned expiration date of August 31, 2012. The reference standard had a reported purity of 99.5%, and was stored in darkness under ambient conditions, 3) Phenol was received from Sigma-Aldrich on August 11, 2006, and was assigned Wildlife International, Ltd. identification number 7686 upon receipt. The reference standard, a solid, was identified as: Phenol, loose crystals, 99+%, ACS Reagent; lot number 15612DE; CAS number 108-95-2, with an assigned expiration date of August 31, 2012. The reference standard had a reported purity of 99.9%, and was stored in darkness under refrigerated conditions, 4) Naphthalene was received from Sigma-Aldrich on August 11, 2006, and was assigned Wildlife International, Ltd. identification number 7687 upon receipt. The reference standard, a solid, was identified as: Naphthalene, 99%; lot number 10601LD; CAS number 91-20-3, with an assigned expiration date of August 31, 2012. The reference standard had a reported purity of 99.8%, and was stored in darkness under ambient conditions. 5) Phenanthrene was received from Sigma-Aldrich on November 2, 2006, and was assigned Wildlife International, Ltd. identification number 7806 upon receipt. The reference standard, a solid, was identified as: Phenanthrene; lot number 07419ME; CAS number 85-01-8, with an assigned expiration date of November 30, 2012. The reference standard had a reported purity of 99.5%, and was stored in darkness under ambient conditions, 6) DDT was received from Sigma-Aldrich on August 14, 2006, and was assigned Wildlife International, Ltd. identification number 7694 upon receipt. The reference standard, a solid, was identified as: 1,1-Bis(4-chlorophenyl)-2,2,2-trichloroethane, 98%; 4,4´-DDT; lot number 02230KY; CAS number 50-29-3, with an assigned expiration date of August 31, 2012. The reference standard had a reported purity of 99.3%, and was stored in darkness under ambient conditions.

DETERMINATION OF RETENTION TIMES
Two combined reference standards (25.0 μL injection volume) were injected prior to and after the test substance to determine retention times. A mean detector offset between the UV and ELSD detectors was 0.037 ± 0.003 minutes (N = 3, CV = 8.1%). Chromatographic separations were achieved using a Zorbax CN column (150 mm x 4.6 mm, 5-mm particle size). The column temperature was maintained at 40°C. The flow rate was 1.00 mL/minute.

REPETITIONS
- Number of determinations: three

EVALUATION
- Calculation of capacity factors k': The capacity factor (k′), was calculated for the test substance and each reference substance using the following equation: k′ = (tR – t0)/t0
where tR was the retention time of the test substance or reference substance and t0 was the column dead time established with thiourea.

- Calculation of retention times: A correlation graph of Log k′ versus Log KOC for the reference standards was plotted and fitted to a regression equation in the form y = mx + b.

- Determination of the log Koc value: The Log KOC for the test substance was calculated by substituting the calculated logarithm of the capacity factor for the test substance into the linear regression equation for the calibration curve. Since the test substance eluted as 13 resolved peaks on the UV detector, a weighted average Log KOC was calculated for each injection of the test substance using the following equation:
Weighted Average Log(KOC) = Σ (LogKOC x Area %)/Σ (Area %)

Type:

Koc

Value:

>= 6.61 L/kg

Type:

log Koc

Value:

>= 5.79 - <= 5.83 other: weighted average

Details on results (HPLC method):

Two combined reference standard solutions comprised of a total of six reference substances was prepared and injected in duplicate (once near the beginning and once near the end of the HPLC sequence). The retention times for one of the reference substances in one of the combined standards, thiourea were used to determine the analytical column dead time (t0) for use in calculating capacity factors (k′) of the remaining reference substances and the test substance. The mean retention time of thiourea was 2.042 minutes. Five additional reference substances contained in the combined reference standard solutions were analyzed. The capacity factors of all the reference substances were calculated based upon their retention times. Prior to initial injection of the combined reference standard, an injection of a reagent blank solution (55%:45% MeOH:H2O, v/v) showed that the reagents used were free of any contaminants and confirmed the peak retention assignments for the reference substances. The three 10.0 mg/mL test substance solutions were sequentially injected. The test substance eluted as 13 resolved peaks on the UV detector and 5 resolved peaks on the ELSD. The mean retention times of each UV peak ranged from 1.231 minutes to 59.451 minutes, while the mean retention times of each ELSD peak ranged from detector offset corrected 1.780 minutes to 59.538 minutes. Prior to the injections of the test substance solutions, a dilution solvent blank solution was injected to identify any solvent background peaks. The capacity factors (k′) of each peak were then calculated based on the corresponding retention time. The corresponding mean adsorption coefficients (Log KOC) for the test substance UV peaks were calculated to range from an unretained (< thiourea) peak to a greater than extrapolated value of 6.61, with an extrapolated overall weighted average of 5.81 ± 0.02 (N = 3, CV = 0.35%).

Validity criteria fulfilled:

yes

Conclusions:

Under the chromatographic conditions specified, the test substance eluted as 13 peaks on the ultraviolet (UV) detector and 5 peaks on the evaporative light scattering detector (ELSD). The corresponding Log Koc for the test substance by UV ranged from unretained (< thiourea) to a greater than extrapolated value of 6.61L/kg, with an extrapolated overall weighted average of 5.81 ± 0.02 (N = 3, CV = 0.35%).

Description of key information

log Koc: 5.81

Key value for chemical safety assessment

Koc at 20 °C:

645 654