Phosphoric acid, 2-ethylhexyl ester

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:

Testing was conducted between 19 May 2011 and 06 August 2011.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.

Qualifier:

equivalent or similar 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:

Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.

Deviations:

no

Qualifier:

equivalent or similar 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:

The determination was carried out using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

other: test item and reference standards prepared in methanol

Radiolabelling:

no

Details on study design: HPLC method:

Procedure:Preparation of sample solutionTest item (0.0543 g) was diluted to 50 ml with methanol and then further diluted by a factor of 20 using methanol (54.3 mg/l).Preparation of dead time solutionThe dead time was determined by measuring the retention time of formamide (purity 99.94%, 609 mg/l solution in mobile phase).Preparation of reference standard solutions:Solution of reference standards were prepared in methanol.Determination of retention timeThe sample, dead time and reference standard solutions were injected in duplicate using the following HPLC parameters:HPLC System:Agilent Technologies 1200, incorporating workstationColumn:Luna CN 5 µm (150 x 4.6 mm id)Column temperature:30ºCMobile phase:methanol : reverse osmosis water (55:45 v/v) Flow-rate:1.0 ml/minInjection volume:10 µlUV detector (standards)210 nmMass spectrometer detector (samples) :Source:electrosprayPolarity:negativeMode:single ion monitoringMass (m/z):209, 321 amuDrying gas flow:13 l/minDrying gas temperature:300°CNebuliser pressure:20 psiCapillary voltage:4500 VFragmentor voltage:100 VConstruction of calibration curve:A calibration curve was constructed from the retention time data of the dead time and reference standard solutions (Figure 12.1 in attachment 1 - attached background material)). The capacity factors (k) for the reference standards were calculated using Equation 12.1.Adsorption coefficient of sample:The capacity factor was calculated using Equation 12.1 See Calculations section within this summary and the log10 Koc value determined using Equation 12.2 with reference to the calibration curve (Figure 12.1 in attachment 1 - attached background material).

Type:

Koc

Value:

< 17.8

Temp.:

30 °C

Type:

log Koc

Value:

< 1.25

Temp.:

30 °C

Transformation products:

not measured

Results

Calibration

The retention times of formamide and the retention times, capacity factors (k) and log₁₀K_ocvalues for the reference standards are shown in the two following tables:

Table 12.2

Dead Time	Retention Time (mins)		Mean Retention Time (mins)
	Injection 1	Injection 2
Formamide	1.980	1.980	1.980

Table 12.3

Standard	Retention Time (mins)		Mean Retention Time (mins)	Capacity Factor (k)	Log10k	Log10Koc
	Injection 1	Injection 2
Acetanilide	2.468	2.470	2.469	0.247	-0.607	1.25
Phenol	2.454	2.455	2.455	0.240	-0.620	1.32
Atrazine	2.867	2.868	2.868	0.448	-0.348	1.81
Isoproturon	3.093	3.094	3.094	0.562	-0.250	1.86
Triadimenol	3.323	3.323	3.323	0.678	-0.169	2.40
Linuron	3.715	3.717	3.716	0.877	-5.71 x 10^-2	2.59
Naphthalene	4.759	4.741	4.750	1.40	0.146	2.75
Endosulfan-diol	3.758	3.749	3.754	0.896	-4.78 x 10^-2	3.02
Fenthion	5.750	5.753	5.752	1.91	0.280	3.31
a-Endosulfan	6.542	6.537	6.540	2.30	0.362	4.09
Phenanthrene	7.856	7.841	7.849	2.96	0.472	4.09
DDT	15.868	15.794	15.831	7.00	0.845	5.63

Adsorption coefficient of sample: The retention times, capacity factors and log₁₀ Koc values determined for the sample are shown in the following table: Table 12.4

Injection	Retention Time (mins)	Capacity Factor (k)	Log10k	Log10Koc
1	1.169	<0.247	<-0.607	<1.25
2	1.172	<0.247	<-0.607	<1.25

Mean log₁₀ K_oc: <1.25

Adsorption coefficient: <17.8

Validity criteria fulfilled:

yes

Conclusions:

The adsorption coefficient (Koc) of the test item has been determined to be less than 17.8 (log10 Koc <1.25).

Executive summary:

Method

The determination was carried outusing the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.

Discussion

The method guideline states that the measurement of adsorption coefficient should be carried out on substances in their ionised and unionised forms. However, the dissociation constants of certain functional groups found in the test item made it impossible to satisfy this criterion. Testing would be required at approximately pH 1 or below for the acidic functional groups to be in the unionised form. As a consequence of this, one of the functional groups will always be present in the ionised form. Therefore, as pH 1 or below is outside the environmental pH range for this test and also experimentally impractical, testing was carried out at approximately neutral pH with the functional groups ionised.

Conclusion

The adsorption coefficient (K_oc) of the test item has been determined to be less than 17.8 (log₁₀K_oc <1.25).

Description of key information

Log Koc = <1.25; Butler & White (2011); OECD 121 (HPLC Estimation Method)

Key value for chemical safety assessment

Koc at 20 °C:

17.8

Additional information

In a single key study, the adsorption coefficient was determined in accordance with OECD Guideline 121 (HPLC Estimation Method). The adsorption coefficient (K_oc) of the test item has been determined to be less than 17.8 (log₁₀ K_oc <1.25).

[LogKoc: 1.25]

[LogKoc: 1.25]