Trihexyl phosphate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23-29 Feb 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

GLP compliance:

yes (incl. QA statement)

Remarks:

Rheinland-Pfalz Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Mainz, Germany

Type of method:

flask method

Key result

Water solubility:

0.25 mg/L

Conc. based on:

test mat. (dissolved fraction)

Loading of aqueous phase:

300 mg/L

Incubation duration:

>= 2 - <= 6 d

Temp.:

20 °C

pH:

>= 6 - <= 7

To determine the dependency of the water solubility on the amount of the test item added, four different loading rates were chosen. The following amounts were added to the flasks (volume of H₂O: 800 mL in each flask):

Flask No.	Amount test item* [µL]	Resulting nominal concentration [mg/L]
1A	255	300
1B	255	300
1C	255	300
2	42.6	50
3	85.1	100
4	426	500

*Calculated from the density of the test item 0.94 g/cm³

Measurements during equilibration: data acquired during equilibration time (flask 1A-C, in duplicate)

Day	Temperature [°C]	pH*	Measured conc. [mg/L]	Conc. Test Item** [mg/L]	Conc. Test Item Mean [mg/L]	Difference to previous sample
1	20.1	6-7	8.03;7.88	0.198;0.195	0.197	-
2	20.2	6-7	9.63;9.75	0.238;0.241	0.240	+21.9%
3	20.5	6-7	10.10;9.96	0.250;0.246	0.248	+3.5%
5***	19.5	6-7	10.95;10.51	0.270;0.259	0.265	+6.7%
6	19.6	6-7	10.16;10.00	0.251;0.247	0.249	-5.9%

*measured using pH paper

**50-fold enrichment and 81% recovery rate from the medium was taken into account

*** the test item solution from the flask 1A (day 4) was not measured as an error occurred during the extraction of the solution

After the analysis of the sample on day 6, the plateau was considered as reached.

Measurements at plateau:

Flask	2	3	4
pH	6.53	6.23	6.36
Measured concentration test item [mg/L]	9.76;9.79	10.46;10.60	12.47;12.44
Enrichment factor	50	50	50
Recovery rate from medium [%]	81	81	81
Concentration test item mean [mg/L]	0.242	0.260	0.308
Nominal concentration test item [mg/L]	50	100	500

The measurements of the days 2-6 were included in the calculation of the mean as the plateau was not reached on day 1 (flask 1A).

Day	Flask	Concentration [mg/L]
2	1B	0.240
3	1C	0.248
5	1B	0.265
6	1C	0.249
6	2	0.242
6	3	0.260
6	4	0.308*

*The value was stated as an outlier and it was not used in the calculation of the mean.

Mean: 0.25 ± 0.01 mg/L (RSD = 4.0%).

Description of key information

0.25 mg/L at 20 °C, pH 6 -7

Key value for chemical safety assessment

Water solubility:

0.25 mg/L

at the temperature of:

20 °C

Additional information

The water solubility of the substance trihexyl phosphate (CAS No. 2528-39-4) was determined using flask method according to OECD 105.