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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27 Dec 2018 to 25 Jan 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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))
Version / remarks:
March 04, 2016
Deviations:
no
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))
Version / remarks:
January 22, 2001.
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: EC Technical Guidance Document on Risk Assessment Part III Chapter 4.3: Use of (Quantitative) Structure Activity Relationships ((Q)SARs) - Soil and Sediment Sorption
Version / remarks:
2003
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Specific details on test material used for the study:
Appearance: Off-white powder
Purity/Composition: 98.8%
Test item storage: At room temperature
Radiolabelling:
no
Test temperature:
35 °C
Analytical monitoring:
no
Key result
Type:
log Koc
Value:
1.83
pH:
2
Key result
Type:
Koc
Value:
67
pH:
2
Key result
Type:
log Koc
Value:
< 1.26
pH:
7
Key result
Type:
Koc
Value:
< 18
pH:
7

pKa Values

No pKa values for basic groups in the molecular structure of the test item in the logarithm range of 1 - 14 were calculated.

The pKa values in the logarithm range of 1 - 14 for acidic groups in the molecular structure of the test item were calculated using the Perrin calculation method.  The results are given in Table 12.

Table 12       

pKa Values of the Test Item

Acidic
ARCOOH pKa3.6

Koc HPLC Method

pH 2

UPLC-UV chromatograms of the test item solution and corresponding blank are shown in Figure 10 and Figure 11, respectively.  In the chromatogram of the test solution, one test item peak was observed.

The results of the HPLC method are given in Table 13.  Figure 12 shows the calibration curve of the log k’ of the reference substances as function of log Koc.  The equation of the regression line was: log k’ = 0.309 × log Koc – 0.814 (r = 0.983, n = 14).

Table 13       

pH 2:  Koc of the Test Item

Substance Retention time (min) log Koc Koc
tr,1 tr,2 mean
Formamide (t0) 0.696 0.694 0.695    
Acetanilide 0.91 0.908   1.26  
Monuron 1.113 1.105   1.99  
Naphthalene 1.452 1.434   2.75  
Benzoic acid phenylester 1.711 1.682   2.87  
Fenthion 2.265 2.214   3.31  
Phenanthrene 2.484 2.43   4.09  
4,4’-DDT 5.887 5.672   5.63  
Test item 1.087 1.087 1.087 1.83 6.7

×

101

pH 7

UPLC-UV chromatograms of the test item solution and the corresponding blank are shown in Figure 13 and Figure 14, respectively.  In the chromatogram of the test item solution, one peak with a retention time of 0.497 minutes was observed.  Under the same analytical conditions, the retention time of acetanilide (log Koc = 1.26) was 0.902 minutes.  It was concluded that the log Koc of test item was < 1.26 (Koc < 1.82 × 101).

Table 14       

pH 7:  Koc of the Test Item

Substance Retention time (min) log Koc Koc
tr,1 tr,2 mean
Acetanilide 0.901 0.903 0.902 1.26  
Test item 0.498 0.495 0.497 < 1.26 < 1.8

×

101
Validity criteria fulfilled:
yes
Conclusions:
The HPLC method using soil-adsorption-reference was applied for the determination of the adsorption coefficient (Koc) of 2-Benzoylbenzoic acid.

The Koc and log Koc values of the test item at pH 2 and pH 7 were:
pH 2: Koc = 67, Log Koc = 1.83
pH 7: Koc = < 18, Log Koc < 1.26
Executive summary:

In this guideline (OECD 121) study conducted with GLP certification, the test material (EC 201-612-2) was determined to have the following adsorption coefficients:

  pH 2 pH 7
Koc log Koc Koc log Koc
Test item 67 1.83 < 18 <1.26

Description of key information

Study conducted to recognised testing guidelines with GLP certification.

Key value for chemical safety assessment

Koc at 20 °C:
67

Additional information

  pH 2 pH 7
Koc log Koc Koc log Koc
Test item 67 1.83 < 18 <1.26