spirodiclofen (ISO);3-(2,4-dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl 2,2-dimethylbutyrate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

In-life initiated/completed: 06-March-1997 to 03-July-1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Study conducted under GLP and in a trusted laboratory. Conducted to OECD Guidelines No. 105
corresponding to EC Guideline A.6 guidelines.

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Principles of method if other than guideline:

The water solubility of Spirodiclofen was determined at 20 °C at pH 4 according to the OECD Guidelines No. 105 corresponding to EC Guideline A.6 as described under column method. It was not possible to determine the solubility as a function of pH as the substance is rapidly hydrolysed at pH-values > 4 *). In order to prove that the saturation equilibrium had been reached, samples were drawn at two different flowrates.

Establishment of the solubility equilibrium and sample preparation:
A glass column containing the test substance deposited on Chromosorb as an inert support
material is connected by means of teflon tubes to a levelling vessel filled with water. The flow-rate is adjusted by means of a restriction capillary between the column and the levelling vessel. The concentration is measured in samples collected at two different flow-rates, a starting flow-rate, tentatively chosen and a lower one of approx. half the rate. If samples collected at the lower rate show a higher apparent solubility then the halving of the flow-rates must continue until the results of the concentration measurements from two series are in agreement. Only then the residence time of the water in the saturation column is sufficient for achieving solubility equilibrium.

In order to prepare the loaded support material portions of 5 g of Chromosorb W/AW were added to a solution of approx. 0.5 g of test substance. The solvent of the resulting suspension was completely evaporated using a rotary evaporator. Residues of solvent were removed overnight in a desiccator connected to a rotary slide-valve oil pump.

The loaded support material was suspended in water and transferred into the glass elution columns (inner diameter 1.2 cm) by rinsing with water. The particles of the loaded Chromosorb settled to form a column bed approx. 35 cm long. The column was connected by means of teflon tubing to a levelling vessel filled with water.

The elution column was placed vertically in a large water-bath thermostated at 20 °C ± 0.5 °C and the stopcock between levelling vessel and restriction capillary was opened. The flow-rate of the effluent from the saturation column was determined by collecting it in measuring flasks.

The test substance tends to be adsorbed on the inner glass surface of the sample bottles. To keep the substance in solution the weight amounts of the collected effluents were added with calculated volumes of acetonitrile producing a concentration of 20% (neglecting volume contraction).

In order to vary the flow-rate capillaries of different length were introduced into the teflon tubing above the column. Afterwards the pH of the water was changed by substitution of the water in the levelling vessel by different buffer.

The effluent was directed into the waste for 40 mins. before a fraction was collected during a time period of 20 mins.and 8 mins, respectively. The concentration of the test substance in this clear fractions was directly measured by means of the HPLC method.

GLP compliance:

yes

Type of method:

column elution method

Key result

Water solubility:

49.7 µg/L

Temp.:

20 °C

pH:

4.08

Key result

Water solubility:

50.6 µg/L

Temp.:

20 °C

pH:

4.08

Table. 1 Water solubility - Summary of results

	acidic citrate buffer c(C6H807xH20)	= 0.01 Mole/L	adjusted to pH 4 with cone. NaOH
pH	4.08		4.08
eluation column flow rate (ml/h)	26.4 - 28.0		41.5-43.0
	code	µg/l	code	µg/l
	9230200	50.2	9230210	49.2
	9230201	51.1	9230211	49.3
	9230202	51.3	9230212	50.5
	9230203	51.0	9230213	50.5
	9230204	51.2	9230214	50.1
	9230205	50.7	9230215	50.4
	9230206	51.5	9230216	48.7
	9230207	51.3	9230217	49.5
	9230208	48.8	9230218	49.5
	9230209	49.3	9230219	48.9
mean	50.6		49.7
rel. standard deviation	1.80		1.34

Conclusions:

The substance is considered effectively insoluble in water for purposes of the chemical safety assessment. At pH >4, hydrolysis will occur with a half life of ca 30 days at pH7.

Executive summary:

The water solubility of Spirodiclofen is 50 µg/L in buffered aqueous solutions at pH 4 and 20 °C. Water solubilities for the pH range between 4 and 9 cannot be determined due to the instability of the substance.

Description of key information

The water solubility of Spirodiclofen is 50 µg/L in buffered aqueous solutions at pH 4 and 20 °C. Water solubilities for the pH range between 4 and 9 cannot be determined due to the instability of the substance.

Key value for chemical safety assessment

Water solubility:

50 µg/L

at the temperature of:

20 °C