4-(2-hydroxyethyl)piperazin-1-ylethanesulphonic acid

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 2012-08-07 to 2014-02-03

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:

2001

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Radiolabelling:

no

Test temperature:

25 ± 1 °C.

Details on study design: HPLC method:

EQUIPMENT
- Pump: Gynkotek Pump M480 G, Autosampler ASI-100
- Type, material and dimension of analytical (guard) column: Reprosil-Pur CN Dr. Maisch, 4.6 mm i.D., 125 mm length, particle size 3 µm
- Detection system: Dionex, UVD 170S

MOBILE PHASES
- Type: mixture of 55% methanol and 45% water, isocratic
- Experiments with additives carried out on separate columns: no
- pH: approx. 6

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

REFERENCE SUBSTANCES
Sodium nitrate
Phenol
Methylbenzoate
Naphthalene
1,2,3-Trichlorbenzene
Phenanthrene
DDT

DETERMINATION OF RETENTION TIMES (see Table 2 below)
- Quantity of test substance / reference substance introduced in the column: One vial was filled with the reference item mix and one vial with the test item solution with concentration 1 g/L

REPETITIONS
- Number of determinations: 6 for reference substances and 3 for test substance


EVALUATION
- Calculation of capacity factors k': The capacity factor k´ for every peak was calculated as follows: k'= (tr -to)/to, with tr = retention time and to=dead time (retention time of sodium nitrate)
- Calculation of retention times: retention time of peaks were used
- Determination of the log Koc value: The calibration function was drawn up from the six measurements of the capacity factors of the reference items. By plotting the (known) log Koc values of the reference items against the mean log capacity factors and performing linear regression, a calibration function was obtained. With the calculated capacity factors for the test item, each log Koc from the three determinations was calculated. Finally, mean and standard deviation of the log Koc were calculated.

Key result

Type:

log Koc

Value:

0.01 dimensionless

Temp.:

25 °C

Key result

Type:

Koc

Value:

1.023 dimensionless

Temp.:

25 °C

Details on results (HPLC method):

- Retention times (mean in minutes) of reference substances used for calibration:
Sodium nitrate: 1.215
Phenole: 2.855
Methylbenzoate: 3.241
Naphthaline: 4.418
1,2,3-Trichlorbenzene: 5.024
Phenanthrene: 6.940
DDT: 13.955
- Details of fitted regression line (log k' vs. log Koc): log k’ = 0.2052 * logKoc - 0.1476 (r2=0.9989)
- Average retention data for test substance: 2.085 (SD = 0.01)

Transformation products:

no

Table 1: Reference items

 

Name	CAS-No.	Concentration injected
Sodium nitrate	7631-99-4	2.00 mg/L
Phenol	108-95-2	4.00 mg/L
Methylbenzoate	93-58-3	2.00 mg/L
Naphthalene	91-20-3	2.00 mg/L
1,2,3-Trichlorbenzene	87-61-6	4.00 mg/L
Phenanthrene	85-01-8	6.00 mg/L
4,4’-DDT	50-29-3	19.7 mg/L

 

 

Table 2: Retention Times Reference Items

 

Compound	RT 1	RT 2	RT 3	RT 4	RT 5	RT 6
	min.	min.	min.	min.	min.	min.
Sodium nitrate	1.213	1.218	1.217	1.205	1.221	1.218
Phenole	2.856	2.857	2.855	2.850	2.856	2.853
Methylbenzoate	3.240	3.245	3.242	3.236	3.241	3.241
Naphthaline	4.415	4.420	4.416	4.411	4.422	4.421
1,2,3-Trichlorbenzene	5.019	5.027	5.022	5.018	5.030	5.030
Phenanthrene	6.927	6.938	6.935	6.934	6.956	6.949
DDT	13.922	13.938	13.938	13.963	13.997	13.972

 

 

Table 3: Mean Retention Times, Capacity Factors Reference Items

 

Compound	RT Mean	RT Stand. Dev.	RT Relative Stand. Dev.	k’
	min.	min.	%
Sodium nitrate	1.215	0.006	0.467	0.000
Phenole	2.855	0.003	0.091	1.3487
Methylbenzoate	3.241	0.003	0.090	1.6666
Naphthaline	4.418	0.004	0.096	2.6348
1,2,3-Trichlorbenzene	5.024	0.005	0.107	3.1341
Phenanthrene	6.940	0.011	0.154	4.7102
DDT	13.955	0.028	0.197	10.4824

 

Table 4: Log k’ and log Koc of Reference Items

 

Compound	log k’	log Koc
Sodium nitrate	-	-
Phenole	0.1299	1.32
Methylbenzoate	0.2218	1.80
Naphthaline	0.4207	2.75
1,2,3-Trichlorbenzene	0.4961	3.16
Phenanthrene	0.6730	4.09
DDT	1.0205	5.63

 

 

Table 5: Retention Times Test Item

 

Peak 1 Test Item	RT
	min.
Measurement 1	2.074
Measurement 2	2.086
Measurement 3	2.094
Mean	2.085
Standard deviation	0.010

 

 

Table 6: Capacity Factor, log Capacity Factor, log Koc Test Item

 

Peak 1 Test Item	k’	log k’	log Koc
Measurement 1	0.7065	-0.1509	-0.016
Measurement 2	0.7164	-0.1448	0.014
Measurement 3	0.7230	-0.1409	0.033
Mean			0.010
Standard deviation			0.025

 

Dead time is 1.215 ± 0.006 minutes, with a RSD of 0.467%.

The RSD of the retention times of the reference items lay all below 0.5 %.

Equation of the regression:

log k' = 0.2052 * logKoc - 0.1476

with a coefficient of determination r2 = 0.9989.

 

Table 7: Validity Criteria and Results

 

Parameter	Criterion	Found	Assessment
Range (Max – Min. log Koc)	< 0.1	0.049	valid
Value within Range of Calibration	1.32 – 5.63	0.010	not valid*

 

* The log Koc of the test item lies outside the range of the reference items.

 

Validity criteria fulfilled:

yes

Conclusions:

The adsorption coefficient of the test item was determined according to the HPLC-method described in guideline 67/548/EEC, annex C.19 and OECD 121 (2001). The Log Koc was determined as 0.010 and lies outside the range of the reference items (range: 1.32 - 5.63). Therefore the log Koc of the test item is stated as < 1.32.

Executive summary:

A GLP-adsorption study according to OECD 121 (2001) was performed with the test substance using a HPLC with a cyanopropyl chemical bound resin on a silica base column. Six reference items with different retention times were used to produce a calibration curve, since retention time on cyanopropyl columns and Koc are correlated. The reference items were chosen on behalf of the retention time of the test item on the column. First, a solution of the reference items was analysed three times with HPLC, then a solution of the test item (three times) and finally three more times the solution with the references. For each reference item, the capacity factor k’ was calculated from the retention time of sodium nitrate and the retention time of the respective reference item. A calibration function was set up using the literature values for Koc of the reference items and the mean capacity factor of the six determinations. In the graph Log k’ versus Log Koc, linear regression was performed, giving r2= 0.9989. The chromatogram of the test item gave one peak (mean RT = 2.085 min). With the help of the calibration, the Log Koc was determined as 0.010 and lies outside the range of the reference items (range: 1.32 – 5.63). Therefore the log Koc of the test item is stated as < 1.32.

Description of key information

The adsorption coefficient of the test item was determined according to the HPLC-method described in guideline 67/548/EEC, annex C.19 and OECD 121 (2001). The Log Koc was determined as 0.010 and lies outside the range of the reference items (range: 1.32 - 5.63).  Therefore the log Koc of the test item is stated as < 1.32.

Key value for chemical safety assessment

Koc at 20 °C:

1.023

Additional information

A GLP-adsorption study according to OECD 121 (2001) was performed with the test substance using a HPLC with a cyanopropyl chemical bound resin on a silica base column. Six reference items with different retention times were used to produce a calibration curve, since retention time on cyanopropyl columns and Koc are correlated. The reference items were chosen on behalf of the retention time of the test item on the column. First, a solution of the reference items was analysed three times with HPLC, then a solution of the test item (three times) and finally three more times the solution with the references. For each reference item, the capacity factor k’ was calculated from the retention time of sodium nitrate and the retention time of the respective reference item. A calibration function was set up using the literature values for Koc of the reference items and the mean capacity factor of the six determinations. In the graph Log k’ versus Log Koc, linear regression was performed, giving r2= 0.9989. The chromatogram of the test item gave one peak (mean RT = 2.085 min). With the help of the calibration, the Log Koc was determined as 0.010 and lies outside the range of the reference items (range: 1.32 – 5.63). Therefore the log Koc of the test item is stated as < 1.32.