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

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

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 A.6 (Water Solubility)

Deviations:

yes

Remarks:

see below "Principles of method if other than guideline"

Principles of method if other than guideline:

The preliminary water solubility test indicated that the column elution method should have been performed as the solubility was less than 1x10-2 g/l. However, due to the physical nature of the test material, it was not possible to use this method; experience has shown that liquid test materials coated onto glass beads cause these beads to adhere together forming a plug within the column and thus preventing water circulation.
Furthermore the results of the preliminary test indicated that the test material was essentially insoluble in water and that the loading rate had no
influence on the final analysed TOC concentration. Therefore the definitive test was performed at a single loading rate only, that of 0.1 g/l.

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Water solubility:

< 1 other: mg TOC/L

Temp.:

20 °C

pH:

7.1

1) Calculation

The total carbon content (TC) and inorganic carbon content (IC) of each sample were measured and calculated automatically by the TOC instrument from curves generated during calibration, The total organic carbon content (TOC) was then calculated by the instrument using the following equation: TOC = TC - IC

where:

TOC = total organic carbon (mg/l)

TC = total carbon content (mg/ l)

IC = inorganic carbon content (mg/l)

2) Results

a) Preliminary test

The total organic carbon (TOC) content of the preliminary test samples are shown in the following table - each value has been corrected for a TOC result of 0.6 mg/l TOC determined for a water blank:

Sample Number	Nominal Loading Rate (g/l)	Mean TOC Content (mg/I)
1	0.10	3.97
2	1.00	2.41
3	10.0	2.54

Negligible response (<0.5 mg/I TOC) was detected on the analysis of a water blank.

b) Definitive test

The TOC concentrations (mg/l) in the sample solutions are shown in the following table:

Solution	Total Organic Carbon Content  (TOC in mg/l)
Sample 1A	<1.0
Sample 1B	<1.0
Sample 2A	<1.0
Sample 2B	<1.0
Sample 3A	2.02 *
Sample 3B	<1.0
Water blank	0.237

* Sample excluded as a statistically significant outlier, Grubbs’ test, P = 0.05, using unrounded data values.

As the water blank represented a significant contribution towards each sample TOC content, it has been subtracted from the definitive test overall results. On excluding Sample 3A as a statistically significant outlier, all TOC contents were below 1.0 mg/l (1.0 x l0^-3 g/l), the limit of quantification applied to the procedure. The results and sample treatment summary are shown in the following table:

Sample Number	Time Shaken at ~30°C (hours)	Time Equilibrated at 20°C (hours)	TOC Content (g/I)	Solution pH
1	24	24	<1.0 x 10^-3	7.1
2	48	24	<1.0 x 10^-3	7.1
3	72	24	<1.0 x 10^-3	7.1

c) Overall result

Solubility less than 1.0 x 10^-3g TOC/l at 20.0 ± 0.5°C (arithmetic mean of three determinations).

Conclusions:

- water solubilty: less than 1 mg TOC/L at 20.0 ± 0.5°C (arithmetic mean of three determinations)
- interpretation of result: slightly soluble (0.1-100 mg/L)

Executive summary:

The determination of the water solubility was carried out using the flask method, EU Method A.6, although the preliminary test indicated that the column elution method should have been performed as the solubility was less than 1x10e-2 g/L. However, due to the physical nature of the test material, it was not possible to use this method - experience has shown that liquid test materials coated onto glass beads cause these beads to adhere together forming a plug within the column and thus preventing water circulation.

Due to the test material being a complex mixture of hydrocarbons, and is also being essentially insoluble in water, analysis of the sample solution was performed monitoring the total organic carbon (TOC) content of the sample solutions only. The water solubilty was determined to be less than 1 mg TOC/L at 20.0 ± 0.5°C, monitoring the total organic carbon (TOC) content of the sample solutions (arithmetic mean of three determinations).

Description of key information

water solubility of the test material: less than 1 mg TOC/L at 20.0 ± 0.5°C (monitoring the total organic carbon (TOC) content of the sample solutions)

Additional information

The determination of the water solubility was carried out using the flask method, EU Method A.6, although the preliminary test indicated that the column elution method should have been performed as the solubility was less than 1.0E0-2 g/l. However, due to the physical nature of the test material, it was not possible to use this method - experience has shown that liquid test materials coated onto glass beads cause these beads to adhere together forming a plug within the column and thus preventing water circulation.

Due to the test material being a complex mixture of hydrocarbons, and is also being essentially insoluble in water, analysis of the sample solution was performed monitoring the total organic carbon (TOC) content of the sample solutions only.

The water solubilty was determined to be less than 1 mg TOC/L at 20.0 ± 0.5°C (arithmetic mean of three determinations).

Water solubility values for constituents of GTL Naphtha were calculated from partition coefficient using a validated calculation method, according to the following equation:

log WS (mmol/l) = -1.02*log K_ow+ 2.60

Additional information is given in the attached QM(P)RF documents.