Hexan-1-ol

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

December 2013

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to an appropriate OECD test guideline. However, no purity data, no pH data, no temperature data and no information on repeatability (number of duplicates) were reported.

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:

no

Remarks:

however the study was covered by ISO 17025 certification

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Radiolabelling:

no

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Agilent 1200 pump, autosampler, and refractive index detector with an EZChrom Elite data system.
- Type:
- Type, material and dimension of analytical (guard) column: Discovery® Cyano 5 µm 250 mm x 4.6 mm analytical column maintained at 40˚C with a 5μm Discovery® Cyano Supelguard™ Cartridge 20 mm × 4.0 mm guard column positioned between the injection system and the analytical column.
- Detection system: Refractive index detection.

MOBILE PHASES
- Type:
- Experiments with additives carried out on separate columns: yes / no: not reported.
- pH: Not reported.
- Solutes for dissolving test and reference substances: methanol.

DETERMINATION OF DEAD TIME
- Method: by inert substances which are not retained by the column (formamide).

REFERENCE SUBSTANCES
- Identity: Phenol, Methyl benzoate, 3,5-Dinitrobenzamide, Naphthalene, 1,2,3-Trichlorobenzene and DDT.

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 5 µl: Test and reference samples were prepared with 0.05 g of test substance in 25 ml of methanol. 5 µl of sample were injected with a flow rate of 1 ml min-1 and a mobile phase of 55% (v/v) methanol and water.
- Quantity of reference substances: 5 µl.
- Intervals of calibration: Not reported.

REPETITIONS
- Number of determinations: Not reported.

EVALUATION
- Calculation of capacity factors k': capacity factor, k, where k = (tr – t0)/t0
- Calculation of retention times: The retention time was determined for each of the reference and test substances, tr, in relation to that of the unretained solute, formamide, t0.
- Determination of the log Koc value: The retention times for a series of reference compounds were determined to form a correlation plot for the calculation of the log organic carbon-water adsorption coefficient for test substances. Linear regression of the organic carbon-water adsorption coefficient (log Koc) of reference substances against the log of capacity factors (log k) of the reference substances determines the linear regression coefficients (a and b). The organic carbon-water adsorption coefficient of a test substance can be calculated by inserting its experimentally determined capacity factor into the below equation:
Log Koc = a + b log k

Type:

log Koc

Value:

1.25

Remarks on result:

other: hexan-1-ol

Type:

Koc

Value:

17.9

Remarks on result:

other: hexan-1-ol

Details on results (HPLC method):

- Retention times of reference substances used for calibration: normal (refer to Table 1 below).
- Details of fitted regression line (log k' vs. log Koc): The data demonstrate a good correlation (R2 = 0.9907) between the experimentally derived capacity factor (k) and the literature log Koc values for the reference substances.
- Average retention data for test substance: mean retention time 4.25 min; log k = -0.64; Koc 17.9, log Koc 1.25.

Table 1. Comparison of experimentally determined log k and literature log K_ocvalues for the reference substances

Substance	Mean retention time (tr) (min)	Log k (log(tr-t0/t­0))	Literature log Koc
Phenol	4.26	1.27	1.32
Methyl benzoate	4.50	1.70	1.80
3,5-Dinitrobenzamide	4.88	2.23	2.31
Naphthalene	5.58	2.90	2.75
1,2,3-Trichlorobenzene	6.27	3.37	3.16
DDT	13.44	5.49	5.63

Table 2. HPLC-derivedlog K_ocvalues for the range of alcohol test substances

Test substances (alcohols)	Mean retention time (tr) (min)	Log k (log(tr-t0/t0))	Koc	Log Koc
1-hexanol	4.25	-0.64	17.9	1.25
1-heptanol	4.48	-0.53	47.3	1.68
1-octanol	4.77	-0.43	123	2.09
1-nonanol	4.96	-0.36	211	2.32
1-decanol	5.58	-0.21	802	2.90
1-undecanol	6.15	-0.11	2006	3.30
1-dodecanol	6.89	0.00	5098	3.71
1-tridecanol	7.85	0.10	13149	4.12
1-tetradecanol	9.08	0.21	33983	4.53
1-pentadecanol	10.69	0.32	89883	4.95
1-hexadecanol	12.89	0.43	249732	5.40

Table 3. Experimentally derived log K_ocvalues for the test substances, comparison of HPLC and adsorption study results

Compound	Koc	Log Koc	Log Koc	Difference	Possible Correction factor^1
	Previous experimental data		HPLC
1-hexanol	10.2	1.01^2	1.25	-0.24	0.17+0.74
1-dodecanol	17980	4.25^3	3.71	0.55
1-tridecanol	50830	4.71^3	4.12	0.59
1-hexadecanol	143000	5.15^3	5.40	-0.24

1 = mean difference between the methods

2 = Gerstl and Helling (1987)

3 = van Compernolle et al. (2006)

Validity criteria fulfilled:

yes

Conclusions:

An adsorption coefficient (Koc) value of 17.9 (log Koc 1.25) was determined in a reliable study conducted according to an appropriate test protocol (OECD 121).

Reference 2

Endpoint:

adsorption / desorption, other

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: The result is sourced from secondary literature. The original reference, with original Koc measurement work, was not available for review and no further information is available.

Type:

log Koc

Value:

1.01

Conclusions:

A log Koc value of 1.01 (equivalent to Koc = 10.2) is reported from a source of non assignable reliability. The original reference, with original Koc measurement work, was not available for review and no further information is available. The method used is not known.

Executive summary:

A log K_oc value of 1.01 (equivalent to K_oc = 10.2) is reported from a source of non assignable reliability. The original reference, with original K_oc measurement work, was not available for review and no further information is available. The method used is not known.

Reference 3

Endpoint:

adsorption / desorption, other

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Remarks:

The result was obtained by the valid application of a well-established predictive method.

Justification for type of information:

Please refer to the associated QMRF and QPRF for details of the model validation, input parameters and other remarks.QSAR validation for this endpoint is discussed further in the Alcohols Environmental Fate Category Report.

Principles of method if other than guideline:

The result was obtained using an appropriate QSAR method.

GLP compliance:

no

Media:

soil

Type:

Koc

Value:

56 L/kg

Remarks on result:

other: Predominantly Hydrophobics method

Type:

Koc

Value:

19.6 L/kg

Remarks on result:

other: Alcohols method

Type:

Koc

Value:

119 L/kg

Remarks on result:

other: Non-hydrophobics method

Conclusions:

Koc values in the range 19.6 - 119 were obtained using three different accepted QSAR calculation methods. The result is considered to be reliable.

Description of key information

Adsorption/desorption: Koc 17.9 for hexan-1-ol (OECD 121)

Key value for chemical safety assessment

Koc at 20 °C:

17.9

Additional information

An estimated K_oc value has been derived in the HPLC adsorption test (OECD 121), supported by various QSAR methods. A K_oc study using HPLC (OECD 121) methodology was conducted for a range of linear aliphatic alcohols in accordance with ISO 17025 (Shell Global Solutions, 2013). The K_oc result for hexan-1-ol from this study was 17.9. The good performance of the OECD 121 method for alcohols in this category is demonstrated by the close results obtained for decan-1-ol by OECD 121 as part of the same study and by the batch equilibrium method (OECD 106), which were within a factor of 2 for the same substance.

It is notable that significant technical difficulties were encountered during method development for the study of decan-1 -ol (CAS 112 -30 -1) in natural standard soils, in that it was not possible to detect sufficient substance and establish equilibrium in non-sterilised soil samples, due to the rapid rate of biodegradation of the test substance by the soil microbiota. The HPLC technique avoids the complications of biodegradation in the soil test substrate.

K_oc values of 56, 19.6 and 119 were obtained using the well-established QSAR calculation method for 'predominantly hydrophobic' substances; the method for 'Alcohol' substances and the method for 'non-hydrophobic' substances respectively, developed by Sabljić and Güsten (1995) for the European Commission, and recommended in EU Guidance. The lower end of the range of predictions is close to the HPLC value. Further details are presented in the endpoint study record.

Additionally, a K_oc value of 10.2 has been sourced from secondary literature for hexan-1-ol (Schuurmann, 2006). The original reference, with original K_ocmeasurement work, was not available for review and no further information is available. The method used is not known.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

Substantial evidence exists within the alcohols Category, in the form of sewage sludge adsorption measurements, literature values, High Performance Liquid Chromatography (HPLC) estimates conducted in accordance with OECD Guideline 121, and a recent OECD Guideline 106 test in soils and a wastewater treatment plant sludge. Predictive methods based on log K_owand MCI have also been explored for members of this Category. The available measured data supports the following conclusions:

- The HPLC predictions correlate very well with the available measured K_oc data, requiring no additional correction.

- Adsorption results in the OECD Guideline 106 study conducted with the structural analogue decan-1 -ol indicate that the alcohol interacts only with the organic carbon in the soils. This confirms the expectation that setting a value of K_oc is sufficient to understand adsorption to the relevant substrates (soil, sediment, sludges).

- There are no confounding factors anticipated for the alcohols in this Category (e.g. unusual interaction with the stationary phase). Based on the structure and simple physical chemistry of hexan-1-ol, there is every reason to believe that the K_oc value obtained from the OECD 121 guideline study is valid and fit-for-purpose.

- Different log K_ow-based QSAR predictions of K_oc vary widely depending on which equation is selected.

- HPLC measured K_oc values across the series show a predictable increase in K_oc value as the carbon number increases. Regression analysis shows that the linear relationship between carbon number and log K_oc value measured using this method is extremely well correlated with very low error.

Reference:

Sabljić A and Güsten H (1995) QSARs for soil sorption. in: overview of structure-activity relationships for environmental endpoints. Hermens JLM (ed), report prepared wtihin the framework of the project "QSAR for prediction of fate and effects of chemicals in the environment", an international project of the Environmental Technologies RTD programme (DG XII/D-1) of the European Commission under contract number EV5V-CT92-0211.

[LogKoc: 1.25]