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Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 25 sept 2007 to 23 jan 2008

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))

Deviations:

no

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))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Radiolabelling:

no

Test temperature:

25ºC (temperature of the HPLC column)

Details on study design: HPLC method:

EQUIPMENT
- Apparatus:
- Type: Varian autosampler 9100
Varian pump ProStar 230
Jones column oven 7990
- Type, material and dimension of analytical (guard) column: LiChrospher CN, particle size 5 µm, 250 mm x 4 mm
- Detection system: Varian UV/VIS detector ProStar 310, 210 nm


MOBILE PHASES
- Type: Water / methanol (45:55; v/v)
- Experiments with additives carried out on separate columns: no
- pH: 6.4
- Solutes for dissolving test and reference substances: no


DETERMINATION OF DEAD TIME
- Method: Sodium nitrate (10.93 mg) was dissolved in 10 mL of acetonitrile to obtain a stock solution. The stock solution (8.5 μL) was diluted with 1 mL of a solvent mixture of water and methanol (45:55; v/v). This sodium nitrate solution was injected twice for the determination of the dead time of the HPLC system.


REFERENCE SUBSTANCES
- Identity:
Sodium nitrate (lot: 452735/151104057, purity: 100.3%, expiry date: 02/2009)
Acetanilide (lot: A0203171, purity: 99.9%, expiry date: 08/2014)
Isoproturon (lot: 61117, purity: 99.0%, expiry date: 11/2012)
Linuron (lot: 20214, purity: 99.5%, expiry date: 01/2008)
Pyrazophos (lot: 40715, purity: 97.0%, expiry date: 06/2008)
Diclofop-methyl (lot: 60510, purity: 96.5%, expiry date: 05/2009)
2.4-DDT (lot: 31127, purity: 98.0%, expiry date: 05/2010)
- Method: Stock solutions of the reference items were prepared as described:
10.94 mg of acetanilide, 10.89 mg of isoproturon, 10.03 mg of linuron, 11.37 mg of pyrazophos, 11.17 mg of diclofop-methyl and 10.49 mg of 2,4-DDT were each dissolved in 10 mL of methanol.
A combined reference solution was prepared by transferring 222 μL of the acetanilide stock solution, 200 μL of the isoproturon stock solution, 130 μL of the linuron stock solution, 1370 μL of the pyrazophos stock solution, 286 μL of the diclofop-methyl stock solution and 794 μL of the 2,4-DDT stock solution into one volumetric flask and diluting to a volume of 10 mL with a solvent mixture of water and methanol (45:55; v/v). This reference solution was injected six times.

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 10 µL. DIMETHYL 2-METHYL GLUTARATE (62.98 mg) was dissolved in acetonitrile (50 mL) to
prepare a stock solution of 1259.6 μg/mL. The stock solution (1 mL) was diluted with a solvent mixture of water and methanol (45:55; v/v) (1 mL) to obtain a test solution of 629.8 μg/mL. The pH value of the test item solution was determined to be 6.9. This test item solution was injected three times.
- Quantity of reference substances: 10 µL
- Intervals of calibration: no data


REPETITIONS
- Number of determinations: The test item solution was injected three times. The reference solution was injected six times and sodium nitrate twice.


EVALUATION
- Calculation of capacity factors k': Based on the OECD test guideline No. 121 and Council Regulation (EC) C.19, the HPLC-method can be used to accurately evaluate log Koc values in the range of 1.5 to 5.0. To this end, the capacity factor (k’) is calculated from the retention time of the reference items, the test item (tR) and an un-retained item (t0):
k’ = (tR - t0)/ t0
where
tR = Retention time of the test item or reference item
t0 = Time a non-sorbed chemical needs to pass the column (dead-time, sodium nitrate solution)

- Calculation of retention times: A calibration graph of the log k' data versus log Koc for the used reference items was plotted. The corresponding logarithms of the capacity factors were calculated and then plotted as a function of the retention time versus the log Koc mean values given in the Annex of the guideline.
- Determination of the log Koc value: A correlation of log k’ versus log Koc of the reference items is plotted using linear regression according to the following equation.
y = a + b . x x = (y - a) / b
where
y = log k’ values
x = log Koc values
a = Y-axis intercept of the regression curve
b = Slope

The log k’ value of the test item was then used to calculate its log Koc value.

Type:

Koc

Value:

8.89

Key result

Type:

log Koc

Value:

0.9

Details on results (HPLC method):

- Retention times of reference substances used for calibration:
Acetanilide: 3.04 min
Isoproturon: 3.55 min
Linuron: 4.28 min
Pyrazophos: 5.38 min
Diclofop-methyl: 6.11 min
2,4-DDT: 8.98 min
- Details of fitted regression line (log k' vs. log Koc): see table 1
linear regression: slope = 0.136
y-axis intercept = 0.098
Coefficient of regression (r) = 0.999
- Graph of regression line attached: yes
- Average retention data for test substance: 2.92 min

Validity criteria fulfilled:

yes

Conclusions:

The log Koc of DIMETHYL 2-METHYL GLUTARATE was found to be < 1.25 (lowest reference item used), which is equal to a Koc value of < 18. The logarithm of the adsorption coefficient of DIMETHYL 2-METHYL
GLUTARATE was extrapolated from the regression curve to be 0.9, which is equal to a Koc value of 8.9.



The log of the adsorption coefficient (KOC) of DIMETHYL 2-METHYL GLUTARATE was estimated to be log KOC < 1.25 which is equal to a KOC value of < 18 using the HPLC method. This value indicates that DIMETHYL 2-METHYL GLUTARATE will not be adsorbed by organic carbon in soil. DIMETHYL 2-METHYL GLUTARATE can be classified to be of very high mobility.

Executive summary:

The determination of the adsorption coefficient (Koc) of DIMETHYL 2-METHYL GLUTARATE was performed according to the OECD Guideline for the Testing of Chemicals, No. 121, Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge using High Performance Liquid Chromatography (HPLC), January, 2001 and the EC Directive 2001/59, C.19.

 

The test item solution and six reference items were injected 3 or 6 times, and the sodium nitrate solution was injected for the determination of the dead time of the HPLC system.

The reference items covered the range of log Koc 1.25 to log Koc 5.63. The log Koc of the test item in soil was calculated using a regression curve and was found to be < 1.25 (lowest reference item used), which is equal to a Koc value of < 18. The logarithm of the adsorption coefficient of DIMETHYL 2-METHYL GLUTARATE was extrapolated from the regression curve to be 0.9, which is equal to a Koc value of 8.9.

 

DIMETHYL 2-METHYL GLUTARATE is very high mobile in soils.

This study is classified as acceptable and satisfies the guideline requirements for an adsorption coefficient study.

Description of key information

The log Koc of DIMETHYL 2-METHYL GLUTARATE was found to be < 1.25 (lowest reference item used), which is equal to a Koc value of < 18. The logarithm of the adsorption coefficient of DIMETHYL 2-METHYL GLUTARATE was extrapolated from the regression curve to be 0.9, which is equal to a Koc value of 8.9.

Key value for chemical safety assessment

Koc at 20 °C:

8.9

Additional information

One experimental study, scored as Klimisch 1, is available (Weissenfeld M., 2008) and selected as a key study.