4-tert-butylpyrocatechol

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 10 sept 2009 to 08 feb 2010

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:

25°C

Details on study design: HPLC method:

EQUIPMENT
- Apparatus:
- Type: Varian autosampler 9100
Varian pump 9010
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 9050, 220 nm


MOBILE PHASES
- Type: Water / methanol (45:55; v/v)
- Experiments with additives carried out on separate columns: no
- pH: 6.47
- Solutes for dissolving test and reference substances: no


DETERMINATION OF DEAD TIME
- Method: 11.68 mg of Sodium nitrate was dissolved in 10 mL of methanol to obtain a stock solution. 500 µL of the stock solution was diluted to 5 mL with a solvent mixture of methanol / water (55:45; v/v). This sodium nitrate solution was injected three times for the determination of the dead time of the HPLC system.


REFERENCE SUBSTANCES
- Identity:
Acetanilide (lot: A0203171, purity: 99.9%, expiry date: 08/2014)
Isoproturon (lot: 61214, purity: 99.0%, expiry date: 12/2012)
Linuron (lot: 60324, purity: 99.5%, expiry date: 03/2012)
Pyrazophos (lot: 70122, purity: 97.0%, expiry date: 01/2011)
Diclofop-methyl (lot: 80218, purity: 98.3%, expiry date: 03/2012)
2.4-DDT (lot: 70821, purity: 99.0%, expiry date: 08/2013)
- Method: Stock solutions of the reference substances were prepared as described:
13.62 mg of acetanilide, 12.05 mg of isoproturon, 10.24 mg of linuron, 12.63 mg of pyrazophos, 14.46 mg of Diclofop-methyl and 10.54 mg of 2,4-DDT were each dissolved in 10 mL of methanol.
A combined reference solution was prepared by transferring
500 µL each of the acetanilide stock solution, the isoproturon stock solution, the linuron stock solution, the pyrazophos stock solution, the diclofop-methyl stock solution and of the 2,4 DDT stock solution into one volumetric flask and diluting to a volume of 5 mL with a solvent mixture of methanol / water (55:45; v/v).


DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 20µL. 35 mg of test item 4-TBC was dissolved in 100 mL of solvent mixture of methanol / water (55:45; v/v) to prepare a stock solution of 350.0 µg/mL. 3 mL of the the stock solution was diluted with the same solvent to 10 mL to obtain a test solution of 105 µg/mL.
- Quantity of reference substances: 20µL
- Intervals of calibration: from 3.13 min (Acetanilide, log Koc = 1.25) to 10.25 min (2,4-DDT, log Koc = 5.63)


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


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.

Key result

Type:

Koc

Value:

23.73

Temp.:

25 °C

Type:

log Koc

Value:

1.37

Temp.:

25 °C

Details on results (HPLC method):

- Retention times of reference substances used for calibration:
Dead time (sodium nitrate): 1.37 min
Acetanilide: 3.13 min
Isoproturon: 3.77 min
Linuron: 4.49 min
Pyrazophos: 5.76 min
Diclofop-methyl: 6.68 min
2,4-DDT: 10.25 min
- Details of fitted regression line (log k' vs. log Koc): log k' = 0.156 log Koc - 0.066 (R² = 0.998)
- Average retention data for test substance: 3.31 min (3.32 min / 3.29 min / 3.32 min)

Validity criteria fulfilled:

yes

Conclusions:

The log of the adsorption coefficient (Koc) of 4-tert-butylpyrocatechol (4-TBC) in soil was calculated to be:
log Koc = 1.37 which is equal to a Koc value of 23.73 using the HPLC method.

The log Koc in sewage sludge could not be determined, as the Koc of the test item was below the Koc of the recommended reference items for sewage sludge in Table 1 of OECD No. 121.

The Koc value is less than 50. This indicates that 4-tert-butylpyrocatechol (4-TBC) is very high mobile in soils.

Executive summary:

In a study (Harlan study, C60394, 2010), the adsorption coefficient in soil and sewage sludge of 4-tert-butylpyrocatechol was determined by HPLC method according to the regulation (EC) n°440/2008, C.19, and the OECD guideline n°121.

 

The test item solution, with a concentration of 105 µg/mL, 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 be1.37,which is equal to a Koc value of 23.73.

The log Koc in sewage sludge could not be determined, as the Koc of the test item was below the Koc of the recommended reference items for sewage sludge in Table 1 of OECD guideline n°121.

 

4-tert-butylpyrocatechol is considered to be highly mobile in soils.

 

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

Description of key information

4-tert-butylpyrocatechol is considered as highly mobile in soils.

Key value for chemical safety assessment

Koc at 20 °C:

23.73

Additional information

Two studies are available (Harlan, 2010; Hemwall, 1965). The first of them, scored as reliability 1 according to Klimisch, was selected as a key study. The adsorption coefficient in soil and sewage sludge of 4 -TBC was determined by HPLC method according to OECD guideline n°121. The log Koc of 4 -TBC in soil was found to be 1.37, which is equal to a Koc value of 23.73. The log Koc in sewage sludge could not be determined. 4 -TBC is highly mobile in soils.

The second study, scored as reliability 2 according to Klimisch and selected as supporting study, investigated the possible adsorption of 4 -TBC on various clay minerals. The adsorption of 4 -TBC by clay minerals is initially quite rapid, and then continue for an extended period of time at a relatively slow rate. The adsorption of 4 -TBC by clay from water is quite strong.

[LogKoc: 1.37]