Melaleuca alternifolia, ext.

Adsorption / desorption

Administrative data

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Test guideline 1

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))

Test guideline 2

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))

GLP compliance:

yes

Type of method:

HPLC estimation method

Test material

Test material information

Constituent 1

Reference substance name:

Melaleuca alternifolia, ext.

EC Number:

285-377-1

EC Name:

Melaleuca alternifolia, ext.

Cas Number:

85085-48-9

Molecular formula:

Not applicable (a generic molecular formula cannot be provided for this specific UVCB substance).

IUPAC Name:

Essential oil of melaleuca alternifolia

Test material form:

liquid

Specific details on test material used for the study:

- Physical state: Liquid.
- Purity: 100%
- Composition of test material: Composition meets ISO Standard 4730-2004 Oil of Melaleuca, terpinen-4-ol type (Tea Tree Oil).
- Lot No.: 1215
- Lab No.: 1536
- Expiration date of the lot: 30 March 2009
- Storage condition of test material: Room temperature, protected from light.

Since the test substance consists of a complex mixture of components, the following materials were obtained for use on this study. The compounds represented the principal components of Tea Tree Oil:
Cineole (Grade: 99%; Supplier: Acros)
Terpinen-4-ol (Grade: 97%; Supplier: Acros)
Alpha-terpinene (Grade: 90%; Supplier: Acros)
Alpha-terpineol (Grade: 99%; Supplier: Acros)
Gamma-terpinene (Grade: 98+%; Supplier: Acros)

Radiolabelling:

no

Study design

Test temperature:

Column temperature: 25°C

HPLC method

Details on study design: HPLC method:

- Reference substances: In order to correlate the measured capacity factor (k) of the test material with its Koc, six reference materials were selected from a list of recommended compounds. These reference compounds were selected to have log10Koc values between 1.3 and 5.6 (see 'Any other information on materials and methods' for further details).

- Method of determination of dead time: An internal standard (formamide) with no retention on the HPLC column was used to determine the deadtime of the HPLC system.

- Procedure: A solution of Tea Tree Oil (552 mg/l in HPLC mobile phase, and also containing I.D.S. (406 mg/l)) was prepared and chromatographed in duplicate, bracketed by samples of the reference mixture, using the following conditions:
- Instrument: Hewlett Packard 1050 Liquid Chromatograph
- Column: Hypersil CPS (25 cm x 4.6 mm internal diameter)
- Column temperature: 25°C
- Mobile phase composition: Acetonitrile:water (55:45 v/v)
- Flow rate: 1.0 ml/min
- Injection volume: 20 μl
- Detector: UV set at 210 nm
Since the test substance consists of a complex mixture, solutions of the component substances were analysed by the method in order to assign identities to the peaks detected.

- Calculations: The mean calibration curve produced was: log10Koc = 3.46 log10k + 3.83, where k = capacity factor = t'r / t0 = (tr - t0) / t0, and t'r = true retention time obtained by subtracting deadtime, or t0, of I.D.S. from measured retention time of sample or reference.

Results and discussion

Adsorption coefficient

Type:

other: log10Koc

Value:

>= 2.3 - <= 5 dimensionless

Remarks on result:

other: Since the test substance was a compex mixture of components, the adsorption coefficient was reported as a range for the compounds.

Results: HPLC method

Details on results (HPLC method):

Table 1 (see 'Any other information on results') presents the primary data from which the calibration curve (see attached Figure 1) was generated. Figures 2 and 3 (see attached) present examples of chromatograms of the standard mixture and test substance generated during this test. The mean calibration curve was used to interpolate the results.

The test substance eluted as a series of peaks between approximately 4 and 10 minutes and consequently the adsorption coefficient was reported as a range for the compounds. The range of log10Koc values obtained for Tea Tree Oil was 2.3 to 5.0.

On analysis of the individual substances, which represented the principal components of the test substance, it was found that: terpinen-4-ol and alpha-terpineol eluted at approximately the same retention time and corresponded to the peak at 4.4 minutes in Tea Tree Oil; and alpha-terpinene and gamma-terpinene also eluted at approximately the same retention time and corresponded to the peak at 6.0 minutes in Tea Tree Oil. The chromatogram obtained for cineole showed that the compound was not detected by the HPLC method.

From the analysis of the individual substances it was established that terpinen-4-ol and alpha-terpineol had a log10Koc value of 2.3, and alpha-terpinene and gamma-terpinene had a log10Koc value of 3.6 (see Table 2 in 'Any other information on results').

Any other information on results incl. tables

Table 1. HPLC determination of log10Koc for Tea Tree Oil.

Sample	Component	tr (minutes)	k	log10k	log10Koc
Standard Run A  (t0 = 3.216 minutes)	Acetanilide	3.756	0.168	-0.775	1.25
	Aniline	4.379	0.362	-0.442	2.07
	Naphthalene	5.347	0.663	-0.179	2.75
	2-Methylnaphthalene	5.980	0.859	-0.066	3.87
	Anthracene	8.049	1.503	0.177	4.41
	DDT	13.249	3.120	0.494	5.63
Sample A (t0 = 3.216 minutes)	Tea Tree Oil	4.382	0.363	-0.441	2.31
		10.094	2.139	0.330	4.98
Sample B (t0 = 3.216 minutes)	Tea Tree Oil	4.383	0.363	-0.440	2.31
		10.101	2.141	0.331	4.98
Standard Run B (t0 = 3.218 minutes)	Acetanilide	3.760	0.168	-0.774	1.25
	Aniline	4.384	0.362	-0.441	2.07
	Naphthalene	5.354	0.664	-0.178	2.75
	2 -Methylnaphthalene	5.989	0.861	-0.065	3.87
	Anthracene	8.064	1.506	0.178	4.41
	DDT	13.275	3.125	0.495	5.63

Linear regression (based on mean of standard runs A and B): log10Koc = 3.46 log10k + 3.83

Table 2. log10Koc for components of Tea Tree Oil.

Component	Retention time (minutes)	log10Koc
Cineole	Not detected	-
Terpinen-4-ol	4.4	2.3
Alpha-terpineol	4.4	2.3
Alpha-terpinene	6.0	3.6
Gamma-terpinene	6.0	3.6

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The range of log10Koc values for Tea Tree Oil was from 2.3 to 5.0.

Executive summary:

A study was performed to determine the adsorption/desorption coefficient of the test substance, tea tree oil. The test was conducted according to the procedure described in EEC Method C19, OECD Method 121. Since the test substance was a complex mixture of components the adsorption coefficient was reported as a range. The range of log10Koc values for tea tree oil was from 2.3 to 5.0.