2-Propenoic acid, 2-hydroxyethyl ester, reaction products with O,O-bis(dialkyalkyl) hydrogen phosphorodithioate and dimethyl phosphonate

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:

07 August 2019 to 27 August 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

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))

Version / remarks:

2001

Deviations:

no

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Test temperature:

Column temperature: 40.0 °C

Details on study design: HPLC method:

OBJECTIVE
- The objective of this study was to experimentally estimate the adsorption coefficient of the test substance in sorbent soil and sewage sludge by a reverse-phase high performance liquid chromatography method.
- The adsorption coefficient (KOC) is defined as the distribution coefficient (Kd, ratio of equilibrium concentrations in sorbent and aqueous phases) normalised to organic carbon content and serves as an indicator of the binding capacity of a chemical onto organic matter or soil and/or sewage sludge.

EXPERIMENTAL DESIGN
- In this experiment, the interaction of the test substance containing polar and/or non-polar functional groups with a dual composition (polar and non-polar sites) HPLC stationary phase mimicked the interaction of the test substance with organic matter present in soil and sludge matrices. The HPLC method was applicable to the test substance since an appropriate detection system (e.g. UV absorbance) was available and the test substance did not react with either the eluent or the stationary phase. The test substance met the other applicability criteria specified in the study protocol for use of the HPLC-estimation method. For a given mobile phase composition and pH, capacity factors were calculated for reference standards of known Log KOC using urea to estimate column dead time (i.e., the retention time of an unretained organic compound). The logarithms of the calculated capacity factors were then plotted against published Log KOC values to establish a linear regression equation.
- Solutions of test item were prepared in 55 % methanol (MeOH): 45 % ultrapure H2O v/v at nominal concentrations of 75.0 and 100 mg/L. The test substance solutions were prepared from a stock solution in MeOH. Six reference standards were prepared in the respective mobile phase at a nominal concentration range (5.00 to 300 mg/L) selected to provide desired ultraviolet (UV) detector response. Of these reference substances, one was used for dead time determination and the other five had known Log KOC values given in the OECD 121 guideline and were used as calibration standards. The reference standard preparations were sequentially injected into an HPLC system followed by a single injection of each test substance solution. The calibration reference standards injection sequence was repeated following the test substance injections. The HPLC system was operated under standardised isocratic, reverse-phase operating conditions per the guideline.

REFERENCE SUBSTANCES
- Six reference calibration standards were prepared and analysed with the test substance.
- The reference substance urea was used to determine the analytical column dead time.
- Five additional reference substances with known Log KOC values found in the OECD 121 guideline were used to prepare a calibration curve for calculating an estimated Log KOC for each of the test substance components.
- The six reference standards are identified in Table 1 (attached).

SOLVENTS AND REAGENTS
- Fisher methanol (MeOH) and acetonitrile (ACN) as well as ultrapure water (collected from a Thermo Scientific GenPure water purification system) were used. All of the solvents were HPLC-grade or higher quality and the following reagents used in the study were ACS reagent grade or better.
- Reagent blanks consisting of 55 % MeOH: 45 % ultrapure water (v/v) were prepared and analysed concurrently with the test and reference substances to identify any chromatographic peaks originating from the solvents and reagents.

MOBILE PHASE PREPARATION
- The guideline specified 55 % MeOH: 45 % ultrapure H2O (v/v) mobile phase composition was prepared in situ by the HPLC system from one reservoir containing manually degassed MeOH and a second reservoir containing manually degassed ultrapure water.
- An aliquot of the eluent leaving the analytical column was collected under the guideline condition of 55:45 (v/v) MeOH: ultrapure water and the pH was measured. The pH of the mobile phase flowing through the column was determined to be 6.3.

PREPARATION OF REFERENCE STOCKS AND STANDARDS
- A primary stock of each reference substance was prepared in either acetonitrile (ACN) or methanol (MeOH). An appropriate amount of each reference stock was fortified into separate 10.0 mL volumetric flasks partially filled with 55 % MeOH: 45 % ultrapure H2O (v/v) dilution solvent and brought to a 10.0 mL final volume with the dilution solvent.
- The reference standard solutions yielded the selected standard nominal concentrations and gave an appropriate detector response for each reference substance.
- Details on the preparation of the reference standard solutions and the nominal concentrations for each stock and standard are provided in Table 2 (attached).

TEST SOLUTION PREPARATION
- A primary stock solution of test item was prepared at a nominal concentration of 1.00 mg/mL
by weighing 0.1000 g of the test substance into a 100-mL volumetric flask. The volumetric flask was
then brought to final volume with MeOH.
- Three subsamples of the stock solution were prepared at a nominal concentration of 75.0 mg/L for analysis by fortifying an appropriate amount (0.750 mL) of the primary stock into separate 10-mL volumetric flasks partially filled with 55% MeOH: 45% ultrapure H2O (v/v) dilution solvent and brought to a 10.0 mL final volume with the dilution solvent. A fourth subsample of the stock solution was prepared at a nominal concentration of 100 mg/L by fortifying an appropriate amount (1.00 mL) into a 10 mL volumetric flask partially filled with 55% MeOH: 45% ultrapure H2O (v/v) dilution solvent. The volumetric flasks were brought to final volume with the dilution solvent. An aliquot of each test substance solution was transferred to an autosampler vial, capped and submitted for HPLC/UV/CAD analysis. Each of the solution injection (10.0 µL) gave an acceptable CAD response. A CAD was required to monitor the test substance since sensitivity by UV was unacceptable.

TEST PROCEDURE
- Retention times of the test substance and reference substances were determined using an Agilent Series 1100 High Performance Liquid Chromatograph (HPLC) equipped with an Agilent Series 1100 variable wavelength ultraviolet (UV) detector and a Thermo Corona Veo charged aerosol detector (CAD).
- A mean detector offset between the UV and CAD detectors was 0.192 ± 0.000707 minutes (N = 3,
CV = 0.369%). Chromatographic separations were achieved using an Agilent Technologies InfinityLab Poroshell 120 EC-CN analytical column (100 mm x 3.0 mm, 2.7 µm particle size). The column
temperature was maintained at 40 °C. The flow rate was 0.500 mL/minute. Prior to test substance analyses, the dead time was determined by injecting the urea reference standard. The instrument parameters are summarised in Table 3 (attached).
- A set of six reference standards (10.0 µL injection volume) were injected prior to and after the test substance injections to determine retention times. The four test substance preparations were each injected following the initial reference standards injections and were analysed under the same chromatographic conditions as the reference standards.

Key result

Type:

log Koc

Value:

4.92 dimensionless

pH:

6.3

Temp.:

40 °C

Remarks on result:

other: results reported as less than urea (Log Koc 0.499) to 4.92

Details on results (HPLC method):

RESULTS
- A total of six reference substances were prepared and injected in duplicate (once at the beginning and once near the end of the HPLC sequence). The retention times for one of the reference substances, urea, was used to determine the HPLC system dead time (t0) for use in calculating capacity factors (k) of the remaining reference substances and the test substance. The mean retention time of the duplicate urea standard injections was 1.099 minutes.
- Five additional reference substances were analysed. The capacity factors of all the reference substances were calculated based upon their retention times. Calculated Log k values for the reference substances are presented in Table 4 (attached). Representative reference standard chromatograms are presented in Figure 2 (attached).
- Before the injection of the reference standards, an injection of each reagent blank solution (55 % MeOH: 45 % ultrapure water (v/v)) showed that the reagents used were free of any contaminants and confirmed the peak retention assignments for the reference substances. A representative chromatogram of one of the reagent blank solutions is presented in Figure 2 (attached).
- The triplicate 75.0 mg/L test item solutions were sequentially injected. The test item eluted as four peaks on the CAD. The test substance was not detected on the UV detector. A fourth test substance solution prepared at 100 mg/L was subsequently injected to verify which peaks were correctly attributed to the test substance. The mean retention times of the peaks on the CAD were 0.907, 1.10, 1.27 and 4.24 minutes. Three peaks had a detector offset retention time less than that of the dead time reference standard, urea (i.e. predicted Log Koc = 0.499(3)) The fourth peak had a mean detector offset retention time of 4.04 corresponding to an offset adjusted Log k of 0.428. The mean adsorption coefficient (Log KOC) value for the fourth test substance peak was 4.92. The calculated mean retention times, capacity factors, and mean adsorption coefficients for the test substance are presented in Table 5 (attached). Representative chromatograms of 75.0 mg/L and 100 mg/L test substance solutions are presented in Figure 3 (attached).

Statistics:

DATA ANALYSIS
- The capacity factor (k), was calculated for the test substance and each reference substance using the equation k = (tr – t0)/t0 where tr was the retention time of the test substance or reference substance and t0 was the column dead time established with urea.
- A correlation graph of Log k versus Log Koc for the reference standards was plotted and fitted to a regression equation in the form y = mx + b.
- The calibration curve is presented in Figure 1 (attached).
- Log Koc values for each test substance peak were calculated by substituting the calculated logarithm of the capacity factor for the test substance peak into the linear regression equation for the applicable calibration curve.

Validity criteria fulfilled:

yes

Conclusions:

Under the chromatographic conditions specified, the test substance eluted as four peaks on the charged aerosol detector (CAD). The corresponding mean adsorption coefficients (Log KOC) for three of the test substance peaks were less than urea (i.e. predicted Log Koc = 0.499) and for the fourth test substance peak was 4.92.

Executive summary:

GUIDELINE

The test was performed based on procedures in 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) and Official Journal of the European Communities No. L225. Method C.19: Estimation of the Adsorption Coefficient (KOC) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC) .

 

METHODS

Solutions of test item were prepared in 55 % methanol (MeOH): 45 % ultrapure H2O v/v at nominal concentrations of 75.0 and 100 mg/L. The test substance solutions were prepared from a stock solution in MeOH. Six reference standards were prepared in the respective mobile phase at a nominal concentration range (5.00 to 300 mg/L) selected to provide desired ultraviolet (UV) detector response. Of these reference substances, one was used for dead time determination and the other five had known Log KOC values given in the OECD 121 guideline and were used as calibration standards. The reference standard preparations were sequentially injected into an HPLC system followed by a single injection of each test substance solution. The calibration reference standards injection sequence was repeated following the test substance injections. The HPLC system was operated under standardised isocratic, reverse-phase operating conditions per the guideline.

 

RESULTS

Under the chromatographic conditions specified, the test substance eluted as four peaks on the charged aerosol detector (CAD). The corresponding mean adsorption coefficients (Log KOC) for three of the test substance peaks were less than urea (i.e. predicted Log Koc = 0.499) and for the fourth test substance peak was 4.92.

Description of key information

Under the chromatographic conditions specified, the test substance eluted as four peaks on the charged aerosol detector (CAD). The corresponding mean adsorption coefficients (Log KOC) for three of the test substance peaks were less than urea (i.e. predicted Log Koc = 0.499) and for the fourth test substance peak was 4.92 (OECD 121 and EU Method C.19).

Key value for chemical safety assessment

Koc at 20 °C:

83 176

Additional information

GUIDELINE

The test was performed based on procedures in 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) and Official Journal of the European Communities No. L225. Method C.19: Estimation of the Adsorption Coefficient (KOC) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC) .

 

METHODS

Solutions of test item were prepared in 55 % methanol (MeOH): 45 % ultrapure H2O v/v at nominal concentrations of 75.0 and 100 mg/L. The test substance solutions were prepared from a stock solution in MeOH. Six reference standards were prepared in the respective mobile phase at a nominal concentration range (5.00 to 300 mg/L) selected to provide desired ultraviolet (UV) detector response. Of these reference substances, one was used for dead time determination and the other five had known Log KOC values given in the OECD 121 guideline and were used as calibration standards. The reference standard preparations were sequentially injected into an HPLC system followed by a single injection of each test substance solution. The calibration reference standards injection sequence was repeated following the test substance injections. The HPLC system was operated under standardised isocratic, reverse-phase operating conditions per the guideline.

 

RESULTS

Under the chromatographic conditions specified, the test substance eluted as four peaks on the charged aerosol detector (CAD). The corresponding mean adsorption coefficients (Log KOC) for three of the test substance peaks were less than urea (i.e. predicted Log Koc = 0.499) and for the fourth test substance peak was 4.92.