(8α,9R,8'''α,9'''R)-1,1'-[(2,3,5,6-tetrafluoro-1,4-phenylene)bis(methylene)]bis(6'-methoxycinchonan-1-ium-9-ol) dibromide

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:

2021-06-23 until 2022-04-20

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))

Version / remarks:

January 2001

Deviations:

no

GLP compliance:

yes

Type of method:

HPLC estimation method

Radiolabelling:

no

Test temperature:

25°C

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Thermo Scientific Dionex HPLC equipped with Ultimate 3000 diode array-detector
- Type, material and dimension of analytical column: Zorbax 300SB-CN, 250 x 4.6 mm, 5 µm. 300 Å, Agilent Technologies
- Detection system: UV (210 nm, 3D field 190-800 nm)

MOBILE PHASES
- Type: methanol : phosphate citrate buffer (50:50, v:v)
- Experiments with additives carried out on separate columns: no
- pH: 5.5 and 7.5
- Solutes for dissolving test and reference substances: methanol (stock solutions of test and reference items), methanol:buffer pH 5.5 (50:50, v:v) and methanol:buffer pH 7.5 (50:50, v:v) (test item solutions, reference compound solutions)

DETERMINATION OF DEAD TIME
- Method: by inert substances which are not retained by the column (formamide)

REFERENCE SUBSTANCES
- Identity: acetanilide, atrazine, endosulfan alcohol, isoproturon, linuron, phenol, triadimenol A
- Purity: of all reference substances ≥97.8%, except acetanilide for which purity is not stated (certified melting point standard)

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 5.0 µg (50 µL of a 100 µg/mL solution)
- Quantity of reference substances: 5.0 µg (50 µL of a 100 µg/mL solutions)
- Intervals of calibration: All reference compounds were injected before (injection A) and after (injection B) the test substance to confirm that retention times had not drifted.

REPETITIONS
- Number of determinations: Two replicates (injections) per reference compounds and test item

EVALUATION
- Calculation of capacity factors k': k' and log k' were calculated using the measured retention times
- Determination of the log Koc value: correlation graph was produced by plotting the Log k' value versus the Log Koc value for each reference compound; literature Log Koc values were obtained from OECD Guideline 121. A Log Koc value for the test item was then extrapolated from the correlation graph.

Key result

Type:

log Koc

Value:

< 1.25

Temp.:

25 °C

Details on results (HPLC method):

For the plots of the Log k’ versus Log KOC of the reference compounds, acceptable linearity was observed, as the r2 value of the linear regression was 0.9523 and 0.9412, for the mobile phase conditions pH 5.5. and pH 7.5, respectively.

The retention time of CA5727 was shorter than any of the reference compounds and the dead time marker formamide for both pH conditions.

It was assumed that the even earlier non-retention of CA5727, as compared to formamide, was a chromatographic effect due to the ionic nature and relatively large molecular size of the test item (molecular weight of CA5727 is 984.75 g/mol, molecular weight of formamide is 45.04 g/mol). During the study, a number of preliminary tests, including the assessment of cyanopropyl HPLC columns with different pore sizes, was carried out but the non-retention of CA5727 (compared to that of formamide) could not be improved.

As CA5727 eluted outside of the calibration range, the adsorption coefficient of CA5727 was estimated based on the adsorption coefficient of acetanilide, the calibrant with the lowest Log Koc of 1.25. Reference substances with Log Koc values lower than acetanilide are not listed in the OECD 121 guideline. Thus, the adsorption coefficient of CA5727 was reported as Log Koc < 1.25 (equates to Koc <17.8).

Capacity kactors (k') and adsorption coefficient (Koc) values for CA5727 using methanol:buffer pH 5.5:

Compound	Retention Time (min)	Average^1 Retention Time (min)	Capacity Factor k’	Log k’	Log KOC
Formamide	2.79	2.80	0.000	Unretained	Unretained*
	2.80
Phenol	3.20	3.20	0.145	-0.839	1.32*
	3.21
Acetanilide	3.25	3.25	0.161	-0.793	1.25*
	3.25
Atrazine	3.99	4.00	0.429	-0.367	1.81*
	4.00
Isoproturon	4.20	4.20	0.501	-0.300	1.86*
	4.20
Triadimenol A	5.38	5.38	0.923	-0.035	2.40*
	5.38
Linuron	5.53	5.54	0.982	-0.008	2.59*
	5.56
Endosulfan alcohol	6.94	6.96	1.489	0.173	3.02*
	6.98
CA5727	2.65	2.66	-0.051	†	†
	2.66

¹ Mean retention time of two injections per sample

* Reference Compound Literature values taken from OECD Guideline 121

† Log k’ and, thus, log K_OC could not be calculated from k’ since k’ was a negative value (i.e. test substance eluted before the retention time marker)

 

Equation of calibration plot (Figure 11):  y = 0.5771x – 1.4846

Coefficient of determination of calibration plot = 0.9523

 

Capacity kactors (k') and adsorption coefficient (Koc) values for CA5727 using methanol:buffer pH 7.5:

Compound	Retention Time (min)	Average^1 Retention Time (min)	Capacity Factor k’	Log k’	Log KOC
Formamide	2.79	2.79	0.000	Unretained	Unretained*
	2.79
Phenol	3.20	3.19	0.144	-0.841	1.32*
	3.19
Acetanilide	3.25	3.25	0.163	-0.788	1.25*
	3.24
Atrazine	4.04	4.04	0.447	-0.349	1.81*
	4.03
Isoproturon	4.27	4.28	0.532	-0.274	1.86*
	4.28
Triadimenol A	5.52	5.52	0.977	-0.010	2.40*
	5.51
Linuron	5.59	5.59	1.004	0.002	2.59*
	5.59
Endosulfan alcohol	7.01	6.99	1.507	0.178	3.02*
	6.98
CA5727	2.52	2.52	-0.096	†	†
	2.52

¹ Mean retention time of two injections per sample

* Reference Compound Literature values taken from OECD Guideline 121

† Log k’ and, thus, log K_OC could not be calculated from k’ since k’ was a negative value (i.e. test substance eluted before the retention time marker)

 

Equation of calibration plot (Figure 11):  y = 0.5802x – 1.4788

Coefficient of determination of calibration plot = 0.9412

 

 

 

Validity criteria fulfilled:

yes

Conclusions:

The log Koc of the test item was found to be <1.25 by using the HPLC method.

Executive summary:

The adsorption coefficient of the substance was studied under GLP to OECD TG 121 using High Performance Liquid Chromatography (HPLC), January 2001. The test item was chromatographed on a cyanopropyl solid phase HPLC column under isocratic conditions using UV-detection (210 nm). Calibration was performed using seven reference compounds of known adsorption coefficient values. The dead time t0 was determined with formamide, an inert substance that is not retained by the HPLC column. Since the substance is ionic with pKa values of 3.4, 4.0 and 11.4, the adsorption coefficients for the test item were estimated using buffered mobile phases at two pH conditions within the environmental relevant range of pH values: One run was carried out using methanol:phosphate citrate buffer pH 5.5 (50:50, v:v) and a second run was performed using methanol:phosphate citrate buffer pH 7.5 (50:50, v:v) as mobile phase. Correlation graphs were produced by plotting the Log k’ value versus the Log Koc value of each reference compound and fitting with a linear regression. Literature Log Koc values were obtained from OECD Guideline 121. Acceptable linear correlations between Log k’ and Log Koc were observed for the reference compounds at the two pH conditions, with coefficients of determination (r2) of 0.9523 and 0.9412, respectively. The test substance eluted prior to all reference substances and formamide, the column dead time marker, at both pH conditions. As the substance eluted outside of the calibration range, the adsorption coefficient was estimated based on the adsorption coefficient of acetanilide, the calibrant with the lowest Log Koc of 1.25. Reference substances with Log Koc values lower than acetanilide are not listed in the OECD 121 guideline. Thus, the adsorption coefficient of the substance was reported as Log Koc <1.25 (equates to Koc <17.8). The substance can be classified as “highly” mobile.

Description of key information

The adsorption coefficient of the substance was studied under GLP to OECD TG 121 using High Performance Liquid Chromatography (HPLC). The test item was chromatographed on a cyanopropyl solid phase HPLC column under isocratic conditions using UV-detection (210 nm). The test substance eluted prior to all reference substances and formamide, the column dead time marker, at both tested pH conditions. As the substance eluted outside of the calibration range, the adsorption coefficient was estimated based on the adsorption coefficient of acetanilide, the calibrant with the lowest Log KOC of 1.25. Thus, the adsorption coefficient of the substance was reported as Log KOC <1.25 (equates to KOC <17.8) and the substance can be classified as “highly” mobile.