Tar bases, coal, lutidine fraction

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

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

Radiolabelling:

no

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Thermo Scientific Dionex
- Type: HPLC
- Type, material and dimension of analytical (guard) column: Zorbax CN, 250 x 4.6 mm, 5 µm, Agilent Technologies
- Detection system: UV detector

MOBILE PHASES
- Type: acetonitrile : water (25:75, v:v)
- Solutes for dissolving test and reference substances: acetonitrile, water

DETERMINATION OF DEAD TIME
- Method: by inert substance formamide which was not retained by the column

REFERENCE SUBSTANCES
- Identity: Acetanilide, atrazine, isoproturon, linuron, phenol, triadimenol A

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: a solution of the test substance in acetonitrile:water (25:75, v:v) with a concentration of 200.0 µg/mL was prepared, and the test substance was injected twice (injection volume 50 µL)
- Quantity of reference substances: reference compound solutions were prepared in acetonitrile:water (25:75, v:v) at nominal concentrations of 200 µg/mL (formamide), 10 µg/mL (acetanilide), 10 µg/mL (atrazine), 40 µg/mL (isoproturon), 20 µg/mL (linuron), 10 µg/mL (phenol) and 50 µg/mL (triadimenol A), and each reference substance was injected twice (injection volume 50 µL)
- Intervals of calibration: 1.25 to 2.59 for log Koc values

REPETITIONS
- Number of determinations: 2

EVALUATION
- Calculation of capacity factors k': k'=(tr - t0)/t0, where tr is the retention time of the reference compound, t0 is the dead time of column
- Calculation of retention times: retention time in UV-detector of each injection (minutes)
- Determination of the log Koc value: following chromatography using acetonitrile:water (25:75, v:v) as mobile phase, a 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 substance was then extrapolated from the correlation graph.

Sample No.:

#1

Type:

Koc

Value:

< 18 dimensionless

Details on results (HPLC method):

- Retention times of reference substances used for calibration: see Table in "Any other information on results"
- Details of fitted regression line (log k' vs. log Koc): obtained equation is y = 0.7116x - 0.7065 (R2 = 0.9542)
- Average retention data for test substance: two peaks were observed for the test substance with average retention times of 5.24 and 6.62 minutes

Table 1: HPLC retention times and Koc values of reference substances and test substance

Reference Items	Log KOC (batch equilibrium)	Mean rt (min)
Formamide	(t0)	3.15
Acetanilide	1.25	7.42
Phenol	1.32	8.12
Atrazine	1.81	14.98
Isoproturon	1.86	22.23
Triadimenol A	2.40	34.92
Linuron	2.59	39.80
Test substance	< 1.25	5.24
Test substance	< 1.25	6.62

Validity criteria fulfilled:

yes

Conclusions:

The retention times of both peaks detected for CA3490A were shorter compared to the retention times of all the reference substances used, which means that CA3490A is outside of the calibration range of the recommended reference compounds. The method for the estimation of the adsorption coefficient by HPLC was not suitable for the test item CA3490A since the test item has a log KOC value < 1.25 (i.e. KOC < 18).

Executive summary:

The adsorption coefficients (KOC) of the substance were estimated using the retention time of the test item measured by HPLC in accordance with OECD TG 121 and under GLP.

Two significant peaks were observed for the substance eluting at retention times of 5.2 minutes and 6.6 minutes. Since the test substance is a complex mixture it is credible that several peaks are observed. The retention times of both peaks detected for the substance were shorter compared to the retention times of all the reference substances used, but it was more retained than formamide used to determine the dead time of the column. The reference substances included acetanilide and phenol which have the lowest log k’ values and log KOC values listed in the OECD guideline 121. This means that the retention time of the test substance is below retention times within the calibration range of the recommended reference compounds.  For this reason, the adsorption coefficient of the substance can be specified to be log KOC < 1.25 and KOC < 18, log KOC of 1.25 being the log KOC of acetanilide, lowest log KOC in the calibration.

Description of key information

The adsorption coefficients (Koc) of CA3490A were estimated using the retention time of the test item measured by HPLC. The retention times of both peaks detected for CA3490A were shorter compared to the retention times of all the reference substances used, which means that CA3490A is outside of the calibration range of the recommended reference compounds. The method for the estimation of the adsorption coefficient by HPLC was not suitable for the test item CA3490A since the test item has a log KOC value < 1.25 (i.e. KOC < 18).  However, CA3490A can be classified as “highly” mobile. The value of 18 L/kg will be used for the KOC will be used in the chemical safety assessment.