4-(cyclohexylamino)butane-1-sulfonic acid

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Remarks:

HPLC

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 29 April 2019 to 21 May 2019

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

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:

2016

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil

Test temperature:

35 °C (column temperature)

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Acquity UPLC system (Waters, Milford, MA, USA)
- Column: Acquity UPLC HSS Cyano, 100 mm x 2.1 mm i.d., dp = 1.8 μm (Waters)
- Detection system: Xevo TQ-S mass spectrometer (Waters)
- Analytical conditions:
- Column temperature: 35 ± 1 °C
- Injection volume: 5 μL
- Mobile phase: 30/70 (v/v) methanol/buffer pH 2 or 7
- Flow: 0.4 mL/min
- UV detection (reference substance): 210 nm
- MS detection
- Ionization source: ESI+
- Cone voltage: 40 V
- Collision energy: 15 eV
- Quantitation (test item): m/z 236.1  m/z 154.0

MOBILE PHASES
- Type: Buffer 1: water adjusted to pH 2 using formic acid, and; Buffer 2: solution of 0.01 M ammonium bicarbonate in water adjusted to pH 7 using formic acid.
- pH: 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 2 and pH 7.

REFERENCE SUBSTANCES
- Identity: Acetanilide (purity >99.9%).
- Log Koc: 1.26 (according to the OECD 121 guideline based on soil adsorption data).

PREPARATION OF SOLUTIONS
- Reference substance solution: A stock solution of the reference substance at a concentration of approximately 1 g/L in methanol was used. The stock solution was diluted to obtain an end solution of 30/70 (v/v) methanol/buffer pH 2 or pH 7.
- Reference blank solution: The blank solution for the mixture of reference substances was 30/70 (v/v) methanol/buffer pH 2 or 7.
- Test substance solution: A 1000 mg/L stock solution of the test item was prepared in methanol. The stock solution was diluted with 30/70 (v/v) methanol/buffer pH 2 or pH 7. The final concentration of the test item solution was 0.025 mg/L.
- Test blank solution: The test item blank solution was 30/70 (v/v) methanol/buffer pH 2 or 7.

Key result

Type:

Koc

Value:

< 18 L/kg

pH:

7

Temp.:

35 °C

Type:

log Koc

Value:

< 1.26 dimensionless

pH:

7

Temp.:

35 °C

Type:

Koc

Value:

< 18 L/kg

pH:

2

Temp.:

35 °C

Type:

log Koc

Value:

< 1.26 dimensionless

pH:

2

Temp.:

35 °C

Details on results (HPLC method):

- pH 2: In the chromatogram of the test item solution, one peak with a retention time of 0.872 minutes was observed. Under the same analytical conditions, the retention time of Acetanilide (log Koc = 1.26) was 1.437 minutes. It was concluded that the log Koc of test item was < 1.26 (Koc < 18).
- pH 7: In the chromatogram of the test item solution, one peak with a retention time of 0.906 minutes was observed. Under the same analytical conditions, the retention time of Acetanilide (log Koc = 1.26) was 1.449 minutes. It was concluded that the log Koc of test item was < 1.26 (Koc < 18).

Validity criteria fulfilled:

not applicable

Conclusions:

The substance has a Koc of <18 L/kg (log Koc 1.26).

Executive summary:

The adsorption coefficient of the test substance was determined in a HPLC screening test according to OECD TG 121 and in compliance with GLP criteria. Solutions of a single reference substance (acetanilide, with a known log Koc value of 1.26 based on soil adsorption data), and the test substance were analysed by HPLC (UPLC-MS) using an Acquity UPLC HSS Cyano column. Based on the calculated pKa values, the HPLC method was performed at pH 2 and pH 7. Retention times of the test substance were considerably lower than retention times of the reference substance at both pH 2 (0.872 min. vs 1.437 min.) and pH 7 (0.906 min. vs 1.449 min.). It was therefore concluded that under the conditions of the test, the log Koc is <1.26 (equivalent to a Koc value <18 L/kg) at both pH values.

Description of key information

The adsorption coefficient of the test substance was determined in a HPLC screening test according to OECD TG 121 and in compliance with GLP criteria. Solutions of a single reference substance (acetanilide, with a known log Koc value of 1.26 based on soil adsorption data), and the test substance were analysed by HPLC (UPLC-MS) using an Acquity UPLC HSS Cyano column. Based on the calculated pKa values, the HPLC method was performed at pH 2 and pH 7. Retention times of the test substance were considerably lower than retention times of the reference substance at both pH 2 (0.872 min. vs 1.437 min.) and pH 7 (0.906 min. vs 1.449 min.). It was therefore concluded that under the conditions of the test, the log Koc is <1.26 (equivalent to a Koc value <18 L/kg) at both pH values.

Key value for chemical safety assessment

Koc at 20 °C:

18