spirodiclofen (ISO);3-(2,4-dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl 2,2-dimethylbutyrate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

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:

draft

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: 95/36/EC

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

soil

Radiolabelling:

no

Test temperature:

oven temperature: 40 °C

Details on study design: HPLC method:

HPLC is performed on analytical columns packed with a commercially available cyanopropyl solid phase containing lipophilic and polar moieties. While passing through the column along with the mobile phase the test substance interacts with the stationary phase. As a result of partitioning between mobile and stationary phases the test substance is retarded. The dual composition of the stationary phase having polar and non-polar sites allows for interaction of polar and non-polar groups of a molecule in a similar way as is the case for organic matter in soil. This enables the relationship between the retention time on the column and the adsorption coefficient on organic matter to be established. This test is useful for chemicals, which are difficult to study in other experimental systems, i.e. a batch equilibrium test. The pH-value has a significant influence on sorption behaviour in particular for polar substances. For agricultural soils pH normally varies between pH 5.5 and 7.5.

Analytical monitoring:

yes

Details on sampling:

The objective of this study was to determine the mobility of Spirodiclofen in soil by estimation of the adsorption coefficient. In the present study the adsorption coefficient K0c of Spirodiclofen was investigated using High-Performance Liquid Chromatography (HPLC). The retention time of the test substance measured in this study was used to calculate Koc -values for Spirodiclofen.

Details on test conditions:

TEST CONDITIONS
- Buffer:Citric acid monohydrate, Merck, No. 1.00244.1000 adjusted to pH 6.0 with a water based solution of Sodium Hydroxide, Merck, No. 6498.1000
- methanol: Promochem, No. 3041 D-46485 Wesel
- Water: cleaned in a Milli-Q unit

Test System:
In the OECD proposal for a new guideline "Estimation of the Adsorption Coefficient (Koc) on Soil using HPLC" [2] the test is required to be carried out using a liquid chromatograph, fitted with a pulse-free pump and a suitable detection device. Commercial cyanopropyl chemically bound resins on a silica base was used. As mobile phase methanol/0.01 M citrate-buffer pH 6.0 (55/45, v/v) was used

Stock solution of the reference substances
An amount of approx. 10 mg of the reference substances was weighed into a 10-mL volumetric flask and diluted to volume with methanol.

Standard solutions:
According to the guideline, the maximum concentration of the test substance should not exceed 1/2 the solubility in the solvent. Therefore the measurements were carried out at concentrations of approx. 5 mg/L. The solvent was similar to the mobile phase of the HPLC method (i.e. methanol / citrate buffer pH 6.0, 55/45, v/v). A total of 0.1 ml_ taken from the standard stock solution was transferred into a 20-mL volumetric flask and diluted to volume with the mobile phase methanol / citrate buffer pH 6.0. The flask was shaken and ultrasonicated for one minute to dissolve the substance.

Key result

Sample No.:

#1

Type:

Koc

Value:

31 037

pH:

6

Matrix:

(methanol / citrate buffer pH 6.0, 55/45, v/v)

Details on results (HPLC method):

HPLC retention time data for the reference compounds are given in Table 1. The dead time (to) was determined to be 1.536 minutes using sodium nitrate. Variability of the retention times from repetitive injections was low, confirming HPLC system stability throughout the analysis period. Representative chromatograms are given in Appendix 2 to Appendix 15. The HPLC solvent blank injections showed a small undisturbing contamination at 2.84 minutes retention time throughout the analyses. The KOC value estimated for Spirodiclofen is 31,037.

Validity criteria fulfilled:

yes

Executive summary:

The adsorption coefficient KOC of the test item on soil was estimated using High Performance Liquid Chromatography (HPLC).
Thirteen reference standards of known K0c were chromatographed on a HPLC system to determine an average capacity factor k'. Sodium nitrate was used to determine the HPLC system dead time (to). A regression line was plotted with the
determined k' values and the known KOC values (log k' vs. log K0c)- Spirodiclofen was chromatographed on the same HPLC system during the same sample sequence as the reference substances, and average k' values were determined. The KOC value for Spirodiclofen was estimated by interpolation from the reference substance regression line. The linear regression of measured k' values against literature K0c values yielded a line with a slope of 2.95, an intercept of 1.97 and a correlation coefficient R2 of 0.9076.
The estimated K0c value for Spirodiclofen is 31,037.

Key value for chemical safety assessment

Koc at 20 °C:

31 037