2-amino-6-methyl-4-propyl-1,2,4-triazolo[1,5-a]pyrimidin-5(4H)-one

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:

2016-01-28 until 2017-04-24

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 (incl. QA statement)

Type of method:

HPLC estimation method

Specific details on test material used for the study:

CA3575 tech., 2-amino-4,5-dihydro-6-methyl-4-propyl-s-triazole-[1,5-a]pyrimidin-5-one

Radiolabelling:

no

Test temperature:

25 °C

Details on study design: HPLC method:

EQUIPMENT
-Apparatus: Thermo Scientific Dionex HPLC equipped with Ultimate 3000 UV-Detector
- Type, material and dimension of analytical column: Zorbax CN, 250 x 4.6 mm, 5 µm, Agilent Technologies with guard column (12.5 x 4.6 mm) of the same material
- Detection system: UV

MOBILE PHASES
- Type: methanol/water 50:50 (v/v)
- Experiments with additives carried out on separate columns: no
- pH: -
- Solutes for dissolving test and reference substances: acetonitrile (stock solutions of reference compounds), methanol/water 50:50 (stock solution of test item, test item solution and reference compounds solutions)

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

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

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 0.25 µg (50 µL of a 5.0 µg/mL solution)
- Quantity of reference substances: 0.5 µg of acetanilide, atrazine and phenol (50 µL of 10 µg/mL solutions), 1.0 µg of linuron (50 µL of a 20 µg/mL solution) and 2.5 µg of isoproturon and triadimenol A (50 µL of 50 µg/mL solutions)
- Intervals of calibration: All reference compounds were injected before (injection A) and after (injection B) the test item 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.

Type:

Koc

Value:

< 18

Details on results (HPLC method):

The retention time of CA3575C was 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 CA3575C is below the calibration range of the recommended reference compounds. For this reason, the adsorption coefficient of CA3575C 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.

 Capacity Factor (k') and Adsorption Coefficient (Koc) Values for CA3575 C

Compound	Retention Time UV-detector of each injection (min)	Average^1Retention Time UV-detector (min)	Capacity Factor k’	Log k’	Log Koc
formamide	3.34	3.34	0.000	Unretained	Unretained*
	3.34
acetanilide	5.18	5.18	0.551	-0.259	1.25*
	5.18
phenol	5.32	5.32	0.593	-0.227	1.32*
	5.32
atrazine	7.40	7.41	1.217	0.085	1.81*
	7.41
isoproturon	8.92	8.92	1.671	0.223	1.86*
	8.92
triadimenol A	11.32	11.31	2.386	0.378	2.40*
	11.30
linuron	14.38	14.38	3.305	0.519	2.59*
	14.38
CA3575C	4.55	4.55	0.362	-0.441	0.89†
	4.55

¹Mean retention time of two injections per sample

* Reference Compound Literature values taken from OECD Guideline 121

† Calculated from equation of calibration plot (see below and Figure 10) although log k’ of CA3575C is below the log k’ values of all reference substances (below calibration)

 

Equation of calibration plot (cfFigure 10): y = 0.5711x – 0.9491

Coefficient of determination of calibration plot = 0.9688

Validity criteria fulfilled:

yes

Conclusions:

The method for the estimation of the adsorption coefficient by HPLC was not suitable for the test item CA3575C since the Koc of the test substance was outside of the range of Koc values covered by the reference substances.

Log Koc of CA3575C < 1.25
Koc of CA3575C < 18

However, CA3575C can be classified as “highly” mobile.

Executive summary:

STUDY DESIGN

The adsorption coefficient of CA3575C was estimated according to the OECD Guideline for Testing of Chemicals, 121, Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC), January 2001.

The test item was chromatographed on a cyanopropyl solid phase HPLC column concurrently with 6 reference compounds of known adsorption coefficient values.

Following chromatography using methanol:water (50:50, v:v) as mobile phase, a correlation graph was produced by plotting the log k’ value versus the log Koc value for each compound. Literature log Koc values were obtained from OECD Guideline 121.

Log Koc values for the test items were then extrapolated from the correlation graph.

RESULTS

A good correlation between log k’ and log Koc is observed for the reference compounds tested with a coefficient of determination r²of 0.9688.

The retention time of CA3575C was 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 CA3575C is below the calibration range of the recommended reference compounds. For this reason, the adsorption coefficient of CA3575C can be specified to be log Koc < 1.25 and Koc < 18 (< 10^1.25), log Koc of 1.25 being the log Koc of acetanilide, lowest log Koc in the calibration.

CONCLUSION

The method for the estimation of the adsorption coefficient by HPLC was not suitable for the test item CA3575C since the test item has a log Koc value < 1.25.

Log Koc of CA3575C < 1.25

                    Koc of CA3575C < 18

However, CA3575C can be classified as "highly" mobile.

Description of key information

Log Koc of <1.25, OECD 121, HPLC estimation method, Derz 2017