2-Thiophenecarboxylic acid, 5-chloro-

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:

8 Feb - 26 Feb 2007

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Determined Koc value for the test substance at pH 6 (0.6) does not exactly meet the range of application of the test guideline (1.5-5.0). However, as the measurement uncertainty was ± 0.5 log units, the value is considered valid. For the test at pH 6 no reference substance with a Koc value above the value for the test substance was available. For this reason result was extrapolated.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Deviations:

no

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))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Radiolabelling:

no

Test temperature:

The column temperature was 40°C, however, this temperature is without influence on the results of the determination. The calibration was done refering to Koc-values of reference substances determined at 25°C.

Details on study design: HPLC method:

EQUIPMENT
- Type, material and dimension of analytical (guard) column: LiChrospher 100 CN particle diameter 5 µm, length 250 mm, inner diameter 4mm
- Column temperature: 40°C
- Detection system: DAD, 220 nm

MOBILE PHASES
- Test pH 2: A, 250 mL buffer solution pH2* + 125 mL water demin. *Buffer solution pH 2: Riedel de haen, Art. No 33541
- Test pH 6: A, 165 mL buffer solution pH 6* + 832 mL water demin. *Buffer solution pH 6: Riedel de Haen, Art. No 33545; B, acetonitrile

DETERMINATION OF DEAD TIME
- Method: by inert substances which are not retained by the column (3 determinations), the mean value of the deadtime with sodium nitrate was 2.970 min (pH2) and 2.613 min (pH6)

REFERENCE SUBSTANCES
- Identity: Sodium nitrate, 2-Nitrobenzamide, 3-Nitrobenzamide, 3,5-Dinitrobenzamide, Triazoxid, Naphthalene, 1,2,3-Trichlorobenzene, 5-Chlorothiophen-2carboxylic acid

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 5 µL injection volume (test concentration 0.16 mg/mL)
- Quantity of reference substances: 5 µL injection volume (test concentration 0.3 to 0.32 mg/mL)

REPETITIONS
- Number of determinations: 3

EVALUATION
- Calculation of capacity factors k': k'= tR-t0/t0
- Calculation of retention times: retention time was measured
- Determination of the log Koc value: from linear regression curve of the reference substances

Details on test conditions:

TEST CONDITIONS
- Buffer:
pH 2 Buffer solution, Riedel de Haen, Art. No. 33541
pH 6 Buffer solution, Riedel de Haen, Art. No. 33545

TEST SYSTEM
- Measuring equipment: determination of the pH value is done with a pH meter equipped with a calibrated single-rod glass electrode.

Sample No.:

#1

Type:

log Koc

Value:

2.3

pH:

2

Temp.:

25 °C

Key result

Sample No.:

#2

Type:

log Koc

Value:

0.6

pH:

6

Temp.:

25 °C

Details on results (HPLC method):

- Retention times of reference substances used for calibration (min):
pH2: 2-Nitrobenzamide (4.684), 3-Nitrobenzamide (5.362), 3,5-Dinitrobenzamide (6.467), Triazoxid (6.809), Naphthalene (19.001), 1,2,3-Trichlorobenzene (23.642)
pH6: 2-Nitrobenzamide (4.691), 3-Nitrobenzamide (5.346), 3,5-Dinitrobenzamide (6.413), Triazoxid (11.904), Naphthalene (18.483), 1,2,3-Trichlorobenzene (23.114)

- Details of fitted regression line (log k' vs. log Koc):
pH2: effective correlation, log k'=a+b*log Koc, k'=tR-t0/t0; a=-1.38743; b=0.69343; r=0.93311
pH6: effective correlation, log k'=a+b*log Koc, k'=tR-t0/t0; a=-1.15289; b=0.65643; r=0.94641

- Average retention data for test substance (min):
pH2: 5-Chlorothiophen-2-carboxylic acid (7.706)
pH6: 5-Chlorothiophen-2-carboxylic acid (3.041)

Validity criteria for the measurement of the adsorption/ desorption:

Target condition according to guideline:	Actual condition according to the study:	Validity criteria met:
Determinations should be run at least in duplicate. The values of log Koc derived from individual measurements should be within a range of 0.25 log unit.	Number of determinations: 3 The values of log Koc between the individual measurements differed <0.25 log unit.	Yes
To correlate the measured HPLC-retention data of a test substance with its adsorption coefficient Koc, a calibration graph of log Koc versus log k’ has to be established. A minimum of six reference points, at least one above and one below the expected value of the test substance should be used.	Two calibration graphs, each with six reference points, were established with log Koc ranging from 1.45 - 3.16. For the test at pH 6 no reference substance with Koc above the measured log Koc of the substance was available, for this reason result was extrapolated.	No
The method is applicable for the determination of log Koc values ranging from 1.5 to 5.0 .	The determined value for the test substance at pH 6 was Koc=0.6 and does not exactly meet the range of application.	No

 

Validity criteria fulfilled:

no

Remarks:

See 'Any other information on results incl. tables'.

Conclusions:

The adsorption coefficient (Koc) of the test substance is log Koc=2.3 at pH2 and log Koc=0.6 at pH6.

Executive summary:

A study was performed to determine the adsorption coefficient (Koc) of the test substance according to EEC-guideline 2001/59/EEC C.19 (OECD 121). To comply with the demand of the guideline (dissociation of ionic test substances) and considering environmental relevance, pH 6 was chosen as pH value for the buffer. For the non-ionic form of the test substance the pH value was set to 2. Therefore, six calibration substances were injected into a HPLC-system at each buffer solution (pH 2, pH 6) under the same analytical conditions (column temperature 40 °C) as the test item. A calibration curve was created by using the measured retention (log k'-values) and the known log Koc-values of the calibration substances for linear regression. For the test at pH 6, no reference substance with a Koc value above the value for the test substance was available. For this reason, the result was extrapolated. From the resulted calibration curve and its equation the log Koc of the substance had been calculated. A significant difference between the results at pH 6 and pH 2 was observed. The adsorption coefficient (Koc) of the test item is log Koc=0.6 (pH 6) and for the non-ionic form of the test substance log Koc=2.3 (pH 2).

Description of key information

A study was performed to determine the adsorption coefficient (Koc) of the test substance according to EEC-guideline 2001/59/EEC C.19 (OECD 121). To comply with the demand of the guideline (dissociation of ionic test substances) and considering environmental relevance, pH 6 was chosen as pH value for the buffer. For the non-ionic form of the test substance the pH value was set to 2. Therefore, six calibration substances were injected into a HPLC-system at each buffer solution (pH 2, pH 6) under the same analytical conditions (column temperature 40 °C) as the test item. A calibration curve was created by using the measured retention (log k'-values) and the known log Koc-values of the calibration substances for linear regression. For the test at pH 6, no reference substance with a Koc value above the value for the test substance was available. For this reason, the result was extrapolated. From the resulted calibration curve and its equation the log Koc of the substance had been calculated. A significant difference between the results at pH 6 and pH 2 was observed. The adsorption coefficient (Koc) of the test item is log Koc=0.6 (pH 6) and for the non-ionic form of the test substance log Koc=2.3 (pH 2).

Key value for chemical safety assessment

Other adsorption coefficients

Type:

other: Koc (pH 6)

Value in L/kg:

4

at the temperature of:

25 °C

Other adsorption coefficients

Type:

other: Koc (pH 2)

Value in L/kg:

200

at the temperature of:

25 °C