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Diss Factsheets

Administrative data

Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
28 August 2017 - 17 December 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report date:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
2000
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.18 (Adsorption / Desorption Using a Batch Equilibrium Method)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
batch equilibrium method
Media:
soil/sewage sludge

Test material

Constituent 1
Chemical structure
Reference substance name:
Mycophenolic acid
EC Number:
246-119-3
EC Name:
Mycophenolic acid
Cas Number:
24280-93-1
Molecular formula:
C17H20O6
IUPAC Name:
6-(4-hydroxy-6-methoxy-7-methyl-3-oxo-1,3-dihydro-2-benzofuran-5-yl)-4-methylhex-4-enoic acid
Test material form:
solid: particulate/powder
Details on test material:
- Batch no. 116-172
- Assay (HPLC) 99.2%
- Analysis date August 12, 2016
- Retest date August 12, 2018
- Solubility in water: 45 mg/I, water (25 °C, pH 5), 710 mg/I, water (25 °C, pH 7) (MSDS)*
- Hydrolysis: 46% (5 d, pH 5, 50 °C); 29% (5 d, pH 7, 50 °C); 37% (5 d, pH 9, 50 °C); hydrolytically unstable, extrapolated half-life at 25 °C between 1 day and 1 year (MSDS)
- Appearance: white to practically white powder (according to Safety Data Sheet provided by the sponsor); light-brown powder (observed on current batch)
Specific details on test material used for the study:
- Batch No. 116-172
- Storage Conditions: 5±3 °C
Radiolabelling:
no

Study design

Test temperature:
laboratory ambient temperatures

Batch equilibrium or other method

Analytical monitoring:
yes
Details on sampling:
not specified
Matrix propertiesopen allclose all
Matrix no.:
#1
Matrix type:
silty clay loam
% Clay:
35.9
% Silt:
61.7
% Sand:
2.5
% Org. carbon:
2.98
pH:
6.63
Matrix no.:
#2
Matrix type:
sandy loam
% Clay:
15.3
% Silt:
25.5
% Sand:
59.3
% Org. carbon:
0.51
pH:
4.3
Matrix no.:
#3
Matrix type:
silty clay loam
% Clay:
31.5
% Silt:
61.9
% Sand:
6.7
% Org. carbon:
0.69
pH:
7.04
Matrix no.:
#4
Matrix type:
other: domestic sludge
% Org. carbon:
34
pH:
6.63
Matrix no.:
#5
Matrix type:
other: mixed (industrial-domestic) sludge
% Org. carbon:
31
pH:
6.46
Details on matrix:
#1: Type 2, Identification no. I 30 02 1, GPS X: 454922.3056, GPS Y: 180016.1719
#2: Type 5, Identification no. I 21 02 1, GPS X: 455135.9908, GPS Y: 175802.8086
#3: Type 6, Identification no. I 27 02 1, GPS X: 460234.7541, GPS Y: 180319.9312
#4: Identification no. sludge 1, source: Balatonfüred Wastewater Treatment Plant; sampling date: July 21, 2017
#5: Identification no. sludge 2, source: Balatonfuzfo Wastewater Treatment Plant; sampling date: August 09, 2017
Details on test conditions:
Preparation of Sludge and Soil Samples for the Test:
Until the start of the experiments soil samples were stored under aerobic circumstances in a dark room where the temperature is monitored.
Sludge samples were dried in an oven. Then they were prepared as the soil samples.
The air-dried soils were sieved to a particle size =2 mm. Then soil and sludge were sterilised in a lab oven (105 °C, 1 hour).
The moisture content of each soil/sludge was determined at 105 °C on three aliquots with the help of a gravimetric moisture balance. For all the calculations the dry mass of soils was used.

Test Conditions:
All experiments were carried out at laboratory ambient temperature in 50 ml polypropylene centrifuge tubes

Control experiments
A control sample with only the test item in 0.01 M CaCl2 solution (no soil/sludge) was subjected to precisely the same steps as the test systems, in order to check the stability of the test item in CaCl2 solution and its possible adsorption on the surfaces of the test vessels.
Blank run per soil/sludge: the same amount of soil/sludge and 0.01 M CaCl2 solution (without test item) were subjected to the same test procedure. This served as a background control during the analysis to detect interfering compounds or contaminated soils/sludges.

Equilibration before the test
Before the day of the experiment the air-dried soil/sludge samples were equilibrated by shaking with a volume of 25 cm3 of 0.01 M CaCl2 overnight (12 h, dark).

Preparation of the test mixtures
Afterwards, a 25 µl of the stock solution II of the test item was added in order to adjust the final volume. This resulted in an initial concentration of the test item of approximately 20 mg/l (C0).
Equilibration
The parallel method (as many replicates as the time intervals) was applied. Each experiment was performed in duplicate.
The mixtures were shaken with the overhead mixer. Aqueous phase of the mixtures was analysed at different equilibration time intervals.

Evaluation
The percentage adsorption (itA) was calculated at each time point (ti) on the basis of the difference between the nominal initial concentration and the measured concentration at the sampling time (ti).
Duration of adsorption equilibrationopen allclose all
Sample No.:
#1
Duration:
48 h
Initial conc. measured:
62.5 mg/kg soil d.w.
Remarks:
soil solution ratio: 1/3 (m/V) soil dry mass: 8.0 g volume aqueous phase 25 cm3 concentration of test item in solution: 20 mg/L temperature: ambient laboratory temperature
Sample No.:
#2
Duration:
54 h
Initial conc. measured:
20 mg/kg soil d.w.
Remarks:
Soil solution ratio: 1/1 (m/V), soil dry mass: 24.95 g, volume aqueous phase 25 cm3, concentration of test item in solution: 20 mg/L
Sample No.:
#3
Duration:
48 h
Initial conc. measured:
62.9 mg/kg soil d.w.
Remarks:
Soil solution ratio: 1/3 (m/V), soil dry mass: 7.95 g, volume aqueous phase 25 cm3, concentration of test item in solution: 20 mg/L
Sample No.:
#4
Duration:
45 h
Initial conc. measured:
500 mg/kg soil d.w.
Remarks:
Soil solution ratio: 1/25 (m/V), soil dry mass: 1.0 g, volume aqueous phase 25 cm3, concentration of test item in solution: 20 mg/L
Sample No.:
#5
Duration:
45 h
Initial conc. measured:
100 mg/kg soil d.w.
Remarks:
Soil solution ratio: 1/5 (m/V), soil dry mass: 5.0 g, volume aqueous phase 25 cm3, concentration of test item in solution: 20 mg/L
Computational methods:
The percentage adsorption was calculated at each time point (itA) and was plotted versus time. The distribution coefficient Kd at equilibrium, as well as the organic carbon normalized adsorption coefficient Koc was also calculated.

Results and discussion

Adsorption coefficientopen allclose all
Key result
Sample No.:
#1
Type:
Koc
Value:
168 other: cm3/g
Matrix:
soil type 2, silty clay loam
% Org. carbon:
2.98
Key result
Sample No.:
#2
Type:
Koc
Value:
557 other: cm3/g
Matrix:
soil type 5, sandy loam
% Org. carbon:
0.51
Key result
Sample No.:
#3
Type:
Koc
Value:
320 other: cm3/g
Matrix:
soil type 6, silty clay loam
% Org. carbon:
0.69
Key result
Sample No.:
#4
Type:
Koc
Value:
37 other: cm3/g
Matrix:
sludge 1
% Org. carbon:
34
Key result
Sample No.:
#5
Type:
Koc
Value:
30 other: cm3/g
Matrix:
sludge 2
% Org. carbon:
31
Key result
Sample No.:
#1
Type:
Kd
Value:
5 other: cm3/g
Matrix:
soil type 2. silty clay loam
% Org. carbon:
2.98
Key result
Sample No.:
#2
Type:
Kd
Value:
2.8 other: cm3/g
Matrix:
soil type 5, sandy loam
% Org. carbon:
0.51
Key result
Sample No.:
#3
Type:
Kd
Value:
2.2 other: cm3/g
Matrix:
soil type 6, silty clay loam
% Org. carbon:
0.69
Key result
Sample No.:
#4
Type:
Kd
Value:
13 other: cm3/g
Matrix:
sludge 1
% Org. carbon:
34
Key result
Sample No.:
#5
Type:
Kd
Value:
9.3 other: cm3/g
Matrix:
sludge 2
% Org. carbon:
31

Results: Batch equilibrium or other method

Recovery of test material:
Mass balance
The mass balance is defined as the percentage of substance which can be analytically recovered after the adsorption test versus the nominal amount of substance at the beginning of the test. Based on the results Mycophenolic acid is considered to be stable in the time scale of the test. Therefore in the course of the experiments only the aqueous phase was analysed.

Concentration of test item in the aqueous phase at the end of adsorption test:
#1: 8.08 µg/ml
#2: 5.63 µg/ml
#3:12.36 µg/ml
#4: 13.27 µg/ml
#5: 7.00 µg/ml

Mass Balance
#2: Soil type 5, soil/solution ratio m/V: 1/1, Mass Balance: 95%
#4: Sludge type 1, soil/solution ratio m/V: 1/25, Mass Balance: 107%
Mass balance (%) at end of adsorption phaseopen allclose all
Sample no.:
#1
Duration:
48 h
% Adsorption:
62
Sample no.:
#2
Duration:
54 h
% Adsorption:
74
Sample no.:
#3
Duration:
48 h
% Adsorption:
41
Sample no.:
#4
Duration:
45 h
% Adsorption:
34
Sample no.:
#5
Duration:
45 h
% Adsorption:
65
Transformation products:
not specified

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
Conclusions:
The soil adsorption of Mycophenolic acid was studied in three different European soils and two different sewage sludges.
The following soil/solution ratios (m/V) were applied: 1/25 (sludge type 1); 1/5 (sludge type 2); 1/3 (soil types 2 and 6); and 1/1 (soil type 5).
Based on the mass balance Mycophenolic acid was considered to be stable in the time scale of the test.
For the screening test three soils and two sludges were used. The initial concentration of the test item was 20 µg/ml. The adsorption equilibrium was reached after about 10 hours agitation. The adsorption coefficients Kd were in the range of 2.2–13 cm3/g and Koc were 30 - 557 cm3/g.
Executive summary:

The adsorption behaviour of the test item, Mycophenolic acid on soil and sludge was determined using three soils and two sewage sludges applying the batch equilibrium method according to OECD Guideline No. 106. The following soils/sludges were used:

Table 1: Characteristics of the soils and sludges

 Type Identification no. GPS X  GPS Y  pH(KCl)  Organic C  Sand %  Silt %  Clay %  soil texture (USDA classes) 
2  I 30 02 1 454922.3056  180016.1719  6.63  2.98  2.5  61.7  35.9  silty clay loam 
5 I 21 02 1  455135.9908  175802.8086  4.30  0.51  59.3  25.5  15.3  sandy loam 
 6 I 27 02 1 460234.7541  180319.9312  7.04  0.69  6.7  61.9  31.5  silty clay loam 
 - sludge 1  -  -  6.63  34  -  -  -  domestic sludge 
-  sludge 2  -  -  6.46  31  -  -  -  mixed (industr./dom.) sludge 

 

Preliminary test:

All the three types of soil and both types of sludge were tested. Initial concentration of the test item was approximately 20 µg/ml.

The optimal soil/solution ratios (m/V) chosen for the main test were 1/1 and 1/3 in case of the soils; 1/5 and 1/25 for the sludges.

Screening test:

Three different soils and two sewage sludges of different origin were used. Initial concentration of the test item was approximately 20 µg/ml. The parallel method was applied.

The adsorption equilibrium was reached after about 10 hours. Based on the mass balance Mycophenolic acid was considered to be stable in the time scale of the test.

The percentage adsorption was calculated at each time point. The adsorption coefficients, Kd and Koc were calculated at equilibrium:

Table 2: Results of the screening test

   Soil type 2  Soil type 5   Soil type 6  Sludge type 1  Sludge type 2 
 Kd, cm3/g 5.0  2.8  2.2  13  9.3 
Koc, cm3/g  168  557  320  37  30