Naphtha (Fischer-Tropsch), light, C4-10-branched and linear

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:

May 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP and in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not effect the quality of the relevant results.

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))

Deviations:

yes

Remarks:

see "Principles of method if other than guideline"

Principles of method if other than guideline:

As the test material had a high affinity for the HPLC column stationary phase, it was necessary to increase the methanol content of the mobile phase to 100% to elute the test material. This was performed at a time greater than the retention time of DDT (25 minutes) such that all components eluted by the amended mobile phase shared a common adsorption coefficient value, that of greater than the highest calibration standard. To allow detection of the test material, fractions of eluent were collected from the HPLC instrument for analysis by gas chromatography (GC).
Furthermore the method guideline states that the measurement of absorption coefficient be performed on the ionised and unionised form of the test material. However in the absence of any dissociating groups, the test material being a mixture of alkanes, the determination was performed at an approximately neutral pH only, on the test material in an unionised form.

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

other: HPLC column: Genesis CN 4µ

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Water solubility: information not available
- Solubility in organic solvents: information not available
- Dissociation constant: information not available
- log Pow: information not available

Radiolabelling:

no

Test temperature:

40°C

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Agilent Technologies 1100, incorporating autosampler and workstation
- Type: HPLC system
- Type, material and dimension of analytical (guard) column: Genesis 4µ CN (250 x 4.6 mm id)
- Detection system: UV detector (210 nm)


MOBILE PHASES
- Type: methanol: water (55:45 v/v)
- Experiments with additives carried out on separate columns: no
- pH: 7.0, obtained using dilute hydrochloric acid and sodium hydroxide
- Solutes for dissolving test and reference substances: methanol


DETERMINATION OF DEAD TIME
- Method: measuring the retention time of formamide (purity≥99.5%, 221 mg/l solution in methanol)


REFERENCE SUBSTANCES
- Identity:

Standard Purity (%) Concentration (mg/l)
--------------------------------------------------------------------
Acetanilide ~99 163
Atrazine 99.2 112
Linuron 99 105
Naphthalene ≥99.0 112
Endosulfan-diol 99.9 103
Fenthion 99.7 256
α-Endosulfan 99.8 101
Phenanthrene ≥97.0 104
Diclofop-methyl 99 104
DDT 98 105



DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 20 µl
- Quantity of reference substances: 20 µl
- Intervals of calibration: information not available


REPETITIONS
- Number of determinations: 2


EVALUATION (for fraction analysis by GC)
- Calculation of capacity factors k': k = (tr-t0)/t0
where:
k = capacity factor
tr= retention time (min)
t0= dead time (min)
- Calculation of retention times: unknown
- Determination of the log Koc value: the log Koc value was determined with reference to the calibration curve

Type:

Koc

Value:

> 427 000

Type:

log Koc

Value:

> 5.63

Details on results (HPLC method):

- Retention times of reference substances used for calibration: Acetanilide 3.877 mins
Atrazine 4.438 mins
Linuron 5.948 mins
Naphthalene 5.790 mins
Endosulfan-diol 7.199 mins
Fenthion 8.141 mins
α-Endosulfan 10.480 mins
Phenanthrene 8.674 mins
Diclofop-methyl 10.268 mins
DDT 20.802 mins
- Details of fitted regression line (log k' vs. log Koc): A=-0.975; B=0.316; r=0.980
- Average retention data for test substance: >26.5 min
- Peaks from the notified chemical eluted after the reference substances Atrazine, Linuron, Naphthalene, Endosulfan-diol, Fenthion, α-Endosulfan, Phenanthrene, Diclofop-methyl, DDT

1) Calibration (GC)

The retention times of formamide and the retention times, capacity factors (k) and log10 Koc values for the reference standards are shown in the two following tables:

Dead Time	Retention Time (min)		Mean Retention Time (min)
	Injection 1	Injection 2
Formamide	3.242	3.242	3.242

Standard	Retention Time (mins)		Mean Retention Time (mins)	Capacity Factor (k)	Log10k	Log10Koc
	Injection 1	Injection 2
Acetanilide	3.881	3.872	3.877	0.196	-0.708	1.25
Atrazine	4.439	4.437	4.438	0.369	-0.433	1.81
Linuron	5.949	5.946	5.948	0.835	-7.86 x 10^-2	2.59
Naphthalene	5.790	5.790	5.790	0.786	-0.105	2.75
Endosulfan-diol	7.195	7.203	7.199	1.221	8.66 x 10^-2	3.02
Fenthion	8.140	8.142	8.141	1.511	0.179	3.31
α-Endosulfan	10.485	10.474	10.480	2.232	0.349	4.09
Phenanthrene	8.673	8.675	8.674	1.676	0.244	4.09
Diclofop-methyl	10.273	10.262	10.268	2.167	0.336	4.20
DDT	20.784	20.819	20.802	5.416	0.734	5.63

2) Remarks

The test material was known to primarily be a complex mixture of alkanes and therefore a majority of the components were not anticipated to absorb in the ultraviolet region. Preliminary assessment of the test material therefore used a refractive index (RI) detector. Unfortunately,

unlike the partition coefficient, fraction collection and GC analysis indicated that negligible components were successfully eluted when maintaining an isocratic mobile phase, in this case at a ratio of 55: 45 v/v methanol: water as required by the method guideline. A gradient increase in the

methanol content of the mobile phase composition was therefore required at a time greater than the retention time of the highest calibration standard to elute a majority of the test material. This requirement for a gradient method invalidated the use of the RI detector. This is since the detector baseline is adversely affected by the continuing shift in the refractive index of the mobile phase caused by the gradient. Therefore the sample was monitored in the far UV region, possibly detecting trace levels of aromatics, and the elution of the test material confirmed by fraction

collection and subsequent GC analysis.

With the exception of the component at a GC retention time of approximately 5.1 minutes, all the major components of the test material were positively detected in the analysed fractions. By GC normalisation, this was equivalent to 91.4% of the test material having been identified as having a log₁₀ K_oc value greater than 5.63. The absence of this single component was noted but concluded not to impact on the validity of the test. This was since a significant majority of the test material, greater than 90%, had been successfully detected and quantified.

The retention time limit value used for the calculation of the adsorption coefficient for those components identified in the collected fractions represents the start of the amended 100% methanol mobile phase. All these components share a common adsorption coefficient value, that of greater than the highest calibration standard.

3) Results

The retention times, capacity factors and  Log₁₀K_ocvalues determined for the sample are shown in the following table:

Peak Number	Injection	Retention Time (mins)	Capacity Factor (k)	Log10k	Log10koc	Mean log10koc
1	1	4.760	0.468	-0.330	2.05	2.05
	2	4.763	0.469	-0.329	2.05
2	1	5.283	0.630	-0.201	2.45	2.45
	2	5.287	0.631	-0.200	2.46
3	1	5.967	0.841	-7.55 x 10^-2	2.85	2.85
	2	5.971	0.842	-7.48 x 10^-2	2.85
4	1	6.883	1.123	5.04 x 10^-2	3.25	3.25
	2	6.892	1.126	5.15 x 10^-2	3.25
5*	1	>25.0	>6.711	>0.827	>5.63	>5.63
	2	>25.0	>6.711	>0.827	>5.63

* Represents components eluted by the amended 100% methanol mobile phase and detected by GC analysis of collected eluent fractions

- mean  Log₁₀K_ocrange: 2.05 to >5.6

- adsorption coefficient range: 111 to >4.27 x 10⁵

Validity criteria fulfilled:

yes

Conclusions:

The adsorption coefficient (Koc) of the test material has been determined to be greater than 111 to >4.27 x 10e5, log10 Koc 2.05 to >5.63, using the HPLC screening method, Method C19 of Commission Directive 2001/59/EC). By fraction collection and subsequent GC analysis, 91.4% of the test material had a log10 Koc value greater than 5.63, calculated from GC normalisation data.

Executive summary:

The determination of the adsorption coefficient was carried out using the HPLC screening method, EU Method C.19. To allow detection of the test material, which had a high affinity for the HPLC column stationary phase, fractions of eluent were collected from the HPLC instrument for analysis by gas chromatography (GC).

The adsorption coefficient (K_oc) of the test material has been determined to be greater than 111 to 4.27 x 10⁵ (log K_oc 2.05 to >5.63). By fraction collection and subsequent GC analysis, 91.4% of the test material had a log₁₀ K_oc value greater than 5.63, calculated from GC normalisation data.

Description of key information

EU method C.19 (HPLC screening method): adsorption coefficient (Koc) >4.27 x 10e5, log Koc>5.63 [at 40°C; the limit value of 5.63 is based on the retention time of the reference substance DDT.

Additional information

The determination of the adsorption coefficient (KOC) was carried out using the HPLC screening method, EU Method C.19. The adsorption coefficient (Koc) of the test material has been determined to be greater than 111 to 4.27 x 105 (log Koc 2.05 to >5.63). By fraction collection and subsequent GC analysis, 91.4% of the test material had a log10Koc value greater than 5.63, calculated from GC normalization data.