4-hydroxybenzophenone

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:

13 November 2018 to 14 November 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: White powder
Purity/Composition: 99.72%
Test item storage: At room temperature desiccated

Radiolabelling:

no

Test temperature:

35°C ± 1°C

Details on study design: HPLC method:

The principle of the test method is similar to that of the OECD guideline no. 117: "Partition coefficient (n-octanol/water), high performance liquid chromatography (HPLC) method". While passing through the column along with the mobile phase the test item interacts with the stationary phase. As a result of partitioning between mobile and stationary phases, the test item is retarded. The dual composition of a cyanopropyl stationary phase, having polar and non-polar sites allows for interaction of polar and non-polar groups of a molecule in a similar way as is the case for organic matter in soil or sewage sludge matrices. This enables the relationship between the retention time on the column and the Koc on organic matter to be established.

According to the guidelines, the determination of the Koc for test items that are ionized for at least 10% within pH 5.5 to 7.5 should be performed with both the ionized and non-ionized form. Therefore, the pKa values of the test item were calculated using the Perrin calculation method (pKalc 5.0, module in Pallas 3.0, CompuDrug International San Francisco, CA, USA). Based on the calculations, the HPLC method was performed at pH 4 and pH 7.

Solutions of reference substances with known log Koc values based on soil adsorption data and the test item were analyzed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the references substances were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Koc value for the test item was calculated by substituting its mean log k’ in the calibration curve. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.

Analytical Method:
Analytical Conditions:
Instrument: Acquity UPLC system (Waters, Milford, MA, USA)
Detector: Acquity UPLC TUV detector (Waters)
Column: Acquity UPLC HSS Cyano, 100 mm × 2.1 mm i.d., dp = 1.8 µm (Waters)
Column temperature: 35°C ± 1°C
Injection volume: 5 µL
Mobile phase : 55/45 (v/v) methanol/buffer pH 4 or 55/45 (v/v) methanol/buffer pH 7
Flow: 0.4 mL/min
UV detection: 210 nm

Details on test conditions:

Buffer Solutions
Acetate buffer pH 4, 0.01 M Solution of 16.7% 0.01 M sodium acetate in water and 83.3% 0.01 M acetic acid in water. Buffer contained 0.0009% (w/v) sodium azide.
Phosphate buffer pH 7, 0.01 M Solution of 0.01 M potassium di-hydrogen-phosphate in water adjusted to pH 7 using 1N sodium hydroxide. Buffer contained 0.0009% (w/v) sodium azide.

Key result

Sample No.:

#1

Type:

Koc

Remarks:

pH 4

Value:

0.021 dimensionless

Key result

Sample No.:

#1

Type:

log Koc

Remarks:

pH 4

Value:

2.33 dimensionless

Key result

Sample No.:

#1

Type:

Koc

Remarks:

pH 7

Value:

0.012 dimensionless

Key result

Sample No.:

#1

Type:

log Koc

Remarks:

pH 7

Value:

2.07 dimensionless

Details on results (HPLC method):

pH 4:
UPLC-UV chromatograms of the test item solution and corresponding blank are shown in Figure 4 and Figure 5, 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 and Figure 6 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’ = 0.335 ´ log Koc – -0.799 (r = 0.98, n = 16).

pH 7
UPLC-UV chromatograms of the test item solution and corresponding blank are shown in Figure 4 and Figure 5, respectively. In the chromatogram of the test solution, one test item peak was observed.
The results of the HPLC method are given in Table 14. Figure 15 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’ = 0.327 ´ log Koc – -0.798 (r = 0.98, n = 16).

pK_a 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 7.

Table 12       

pKa Values of the Test Item

Acidic
PHENOL	pKa8.1

Table 13       

pH 4:  Koc of the Test Item

Substance	Retention time (min)			log Koc	Koc
	tr,1	tr,2	mean
Formamide (t0)	0.703	0.702	0.703
Acetanilide	0.95	0.95		1.26
Monuron	1.199	1.199		1.99
2,5-Dichloroaniline	1.403	1.404		2.55
Naphthalene	1.647	1.649		2.75
Benzoic acid phenylester	1.963	1.966		2.87
Fenthion	2.754	2.758		3.31
Phenanthrene	3.049	3.054		4.09
4,4’-DDT	8.111	8.16		5.63
Test item – peak 1	1.374	1.378	1.376	2.33	210

Table 14       

pH 7:  Koc of the Test Item

Substance	Retention time (min)			log Koc	Koc
	tr,1	tr,2	mean
Formamide (t0)	0.702	0.7	0.701
Acetanilide	0.94	0.939		1.26
Monuron	1.178	1.177		1.99
2,5-Dichloroaniline	1.366	1.363		2.55
Naphthalene	1.612	1.608		2.75
Benzoic acid phenylester	1.93	1.924		2.87
Fenthion	2.605	2.592		3.31
Phenanthrene	2.915	2.901		4.09
4,4’-DDT	7.335	7.292		5.63
Test item – peak 1	1.23	1.227	1.229	0.752	120

Validity criteria fulfilled:

yes

Conclusions:

The HPLC method using soil-adsorption-reference data was applied for the determination of the adsorption coefficient (Koc) of 4-Hydroxy-benzophenone.

pH 4: Koc 210; log Koc 2.33

pH 7: Koc 120; log Koc 2.07

Executive summary:

In this guideline (OECD 121) study conducted with GLP certification, the test material (EC 214-507-1) was determined to have the following adsorption coefficients:

	pH 4		pH 7
	Koc	log Koc	Koc	log Koc
Test item – peak 1	210	2.33	120	2.07

Description of key information

Study conducted to recognised testing guidelines with GLP certification.

Key value for chemical safety assessment

Koc at 20 °C:

120

Additional information

Koc 120 at 20 °C at pH 7

Koc 210 at 20 °C at pH 4