mecoprop-P (ISO); (R)-2-(4-chloro-2-methylphenoxy)propionic acid

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 November 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

other: CIPAC Method 'MT 157/water solubility'

Deviations:

no

GLP compliance:

yes

Type of method:

flask method

Key result

Water solubility:

860 mg/L

Conc. based on:

test mat.

Incubation duration:

>= 0.5 - <= 4 h

Temp.:

20 °C

pH:

7

Remarks on result:

completely miscible

Water solubility:

780 mg/L

Conc. based on:

test mat.

Incubation duration:

>= 0.5 - <= 4 h

Temp.:

20 °C

pH:

3

Details on results:

Determination of the solubility in bidistilled water: According to these data, the solubility of the test material, rounded off to two significant digits, is 860 mg x L^-1.

Determination of the solubility in water adjusted to pH 3.0: Measurement in a potassium hydrogen phthalate buffer.
These values indicate that the solubility of the test material in the acid buffer is higher than in bidistilled water. The contrary is expected. Therefore we can assume that the composition of this special buffer influences the solubility.
In order to obtain measuring results that are influenced as little as possible by the presence of foreign ions, in another experiment the pH value of the water was adjusted using a strong inorganic acid.

Measurement in hydrochloric solution of pH 3.0: Calculating the mean from two measuring series we found that 780 mg x L^-1 test material dissolve in water of pH 3 at 20 °C.

Determination of the solubility in the alkaline range: These values show that the water solubility of the test material at pH 9.0 and 9.2 is greater than 50 %.

 Results of the Determination of the Solubility in Bidistilled Water

 

Sample	Stirring Period at Test Temperature	Mg Test Material x L^-1
A1	0.5 h	901
A2	1.0 h	865
A3	2.0 h	854
A4	4.0 h	865
		Mean = 871
B1	0.5 h	824
B2	1.0 h	839
B3	2.0 h	850
B4	4.0 h	871
		Mean = 846

Determination of Solubility in Water Adjusted to pH 3 Measurement in a Potassium Hydrogen Phthalate Buffer

Sample	Stirring Period at Test Temperature	Mg Test Material x L^-1
A1	0.5 h	1,232
A2	1.0 h	1,210
A3	2.0 h	1,167
A4	18.0 h	1,157
		Mean = 1,192
B1	0.5 h	1,172
B2	1.0 h	1,150
B3	2.0 h	1,182
B4	18.0 h	1,153
		Mean = 1, 164

Measurement in Hydrochloric Solution pH 3

Sample	Stirring Period at Test Temperature	mg Test Material x L^-1
A1	0.5 h	781
A2	1.0 h	770
A3	2.0 h	776
A4	4.0 h	789
		Mean = 779
B1	0.5 h	776
B2	1.0 h	771
B3	2.0 h	774
B4	4.0 h	792
		Mean = 778

Determination of the Solubility in the Alkaline Range

Preparation	Test Material	mg 6 N NaOH	%	pH value	Density
A	2,662.75	2,463.52	51.90	9.0	1.2241
A	2,623.80	2,429.19	51.88	9.2	1.2257

Conclusions:

Under the conditions of the study, the solubility data of the test material at 20 °C was 860 mg/L dissolved in bidistilled water and 780 mg/L dissolved in water adjusted on an average of pH 3.

Executive summary:

The water solubility of the test material was assessed according to guideline CIPAC Method 'MT 157/2 using a flask method and in compliance with GLP.

The test material was added in excess to the water and stirred intensively for half an hour, in one preparation at 10 °C above the test temperature, in another at 10 °C below the test temperature. Then in both preparations the test temperature was adjusted and stirring continued. Beginning from half an hour after the adjustment of the test temperature of 20 °C, samples were drawn from both preparations at various time intervals. The samples consisting of active ingredient suspensions were cleared from solid particles by pressure filtration using the apparatus Satorius SM 16 249 and a 0.2 µ polytetrafluorethylene membrane filter. The resulting clear solutions were analysed using the HPLC analytical method. Determination of the solubility in water adjusted to pH 3, measurement in hydrochloric solution of pH 3 and determination of the solubility in the alkaline range were also assessed.

Under the conditions of the study, the solubility data of the test material at 20 °C was 860 mg/L dissolved in bidistilled water and 780 mg/L dissolve in water adjusted on an average of pH 3. In the alkaline range (pH >9), the test material forms salts. Aqueous solutions containing more than 50 % of  the test material as sodium salts, did not show a tendency to crystallisation.

Reference 2

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 February 1999 to 22 June 1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 830.7840 (Water Solubility)

Deviations:

no

GLP compliance:

yes

Type of method:

flask method

Key result

Water solubility:

880 mg/L

Conc. based on:

test mat.

Incubation duration:

24 h

Temp.:

20 °C

Remarks on result:

other: pH not specified

Water solubility:

6.65 g/L

Conc. based on:

test mat.

Incubation duration:

24 h

Temp.:

20 °C

pH:

4

Water solubility:

> 250 g/L

Conc. based on:

test mat.

Incubation duration:

24 h

Temp.:

20 °C

pH:

7

Water solubility:

> 250 g/L

Conc. based on:

test mat.

Incubation duration:

24 h

Temp.:

20 °C

pH:

10

Details on results:

The detector calibration was found to be linear over the range 0 to 216 mg/L of standard solutions in mobile phase with a regression coefficient of 1.0000
The solubilites were found to be:
Purified water 880 ± 16 mg/L
pH 4 buffer solution 6.65 ± 0.24 g/L
pH 7 buffer solution > 250 g/L
pH 10 buffer solution > 250 g/L
No peaks were observed in the chromatograms of the blank solutions indicating that the analytical method was free from interference.

Preliminary Results

Solvent System	Volume of Solvent (mL)	Solubility (mg/L)
Purified water	20	> 500
pH 4 buffer	10	> 1 000
pH 4 buffer	5	> 2 000
pH 4 buffer	2	> 5 000

Flask Test

Standard Calibration for the Test Material by HPLC

Standard Concentration (mg/L)	Peak Area
21.60	306.5
43.19	619.1
86.39	1229
129.6	1871
172.8	2491
216.0	3110

Linear regression (including x = 0, y = 0)

y = 14.4x - 4.56

r = 1.0000

x = concentration

y = peak area

 

HPLC Analysis of Samples for the Solubility Test in Purified Water for the Test Material

Sample	Peak Area	CA (mg/L)	Dilution Factor	CB (mg/L)
129.6 mg/L std	1870	-	-	-
Sample 1A	841.0	58.40	15	876.0
Sample 1B	824.0	57.22	15	858.3
129.6 mg/L std	1863	-	-	-
129.6 mg/L std	1863	-	-	-
Sample 2A	832.6	58.00	15	870.0
Sample 2B	846.2	58.94	15	884.1
129.6 mg/L std	1858	-	-	-
129.6 mg/L std	1856	-	-	-
Sample 3A	858.9	60.22	15	903.4
Sample 3B	846.7	59.37	15	890.5
129.6 mg/L std	1840	-	-	-

 

HPLC Analysis of Samples for the Solubility Test in pH 4 Buffer Solution for the Test Material

Sample	Peak Area	CA (mg/L)	Dilution Factor	CB (mg/L)
129.6 mg/L std	1858	-	-	-
Sample 1A	1923	134.1	50	6703
Sample 1B	1860	129.6	50	6482
129.6 mg/L std	1861	-	-	-
129.6 mg/L std	1861	-	-	-
Sample 2A	1992	138.2	50	6910
Sample 2B	1803	125.1	50	6255
129.6 mg/L std	1874	-	-	-
129.6 mg/L std	1840	-	-	-
Sample 3A	1929	135.0	50	6748
Sample 3B	1939	135.6	50	6782
129.6 mg/L std	1864	-	-	-

 

Measurements of Solubility in Purified Water at 20 °C

Sample No.	Time (Days)		Concentration (mg/L)	Mean Concentration (mg/L)	pH
	Held at 30 °C	Equilibrated at 20 °C
1A, 1B	1	1	876, 858	867	2.94, 2.94
2A, 2B	2	1	870, 884	877	2.96, 2.94
3A, 3B	3	1	903, 891	897	2.93, 2.93

Water solubility (determined as mean of all samples) = 880 ± 16 mg/L

(C. of V. = 1.8 %)

determined as mean of all samples

 

Measurements of Solubility in pH 4 Buffer Solution at 20 °C

Sample No.	Time (Days)		Concentration (mg/L)	Mean Concentration (mg/L)	pH
	Held at 30 °C	Equilibrated at 20 °C
1A, 1B	1	1	6.70, 6.48	6.59	4.08, 4.04
2A, 2B	2	1	6.91, 6.26	6.58	4.09, 4.07
3A, 3B	3	1	6.75, 6.78	6.77	4.08, 4.07

Water solubility (determined as mean of all samples) = 6.65 ± 0.24 g/L

(C. of V. = 3.6 %)

Conclusions:

Under the conditions of the study, the solubility of the test material was found to be 880 mg/L in purified water, 6.65 g/L in pH 4 buffer solution, greater than 250 g/L in pH 7 buffer solution, and greater than 250 g/L in pH 10 buffer solution.

Executive summary:

The water solubility of the test material was assessed according to OECD Test Guideline 105 and EU Method A.6. and in compliance with GLP using a flask method.

Samples of the test material (pure grade) were weighed into separate Wheaton vials. The appropriate solvent (30 mL) was added to the flasks, which were purged with nitrogen, sealed and mixed at 30 °C for 1, 2 and 3 days (it was necessary to adjust the pH 4 samples with a few drops of 1M sodium hydroxide to the intended pH value at the start of the tests). On each occasion duplicate vials were transferred to equilibrate at 20 °C for 24 hours. The samples were then filtered through Whatman filter papers, and a subsample (1 mL) of each filtrate was diluted to volume (15 mL for the samples in purified water, and 50 mL for the samples in pH 4 buffer) with mobile phase for analysis by high performance liquid chromatography (HPLC).

The detector calibration was found to be linear over the range 0 to 216 mg/L of standard solutions in mobile phase with a regression coefficient of 1.0000

No peaks were observed in the chromatograms of the blank solutions indicating that the analytical method was free from interference.

Under the conditions of the study, the solubility of the test material was found to be 880 mg/L in purified water, 6.65 g/L in pH 4 buffer solution, greater than 250 g/L in pH 7 buffer solution, and greater than 250 g/L in pH 10 buffer solution.

Reference 3

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11 April 1990 to 20 August 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EPA FIFRA Subdivision D § 63-8

Deviations:

no

GLP compliance:

yes

Type of method:

flask method

Key result

Water solubility:

858.6 mg/L

Conc. based on:

test mat.

Incubation duration:

<= 7 d

Temp.:

20 °C

pH:

>= 2.78 - <= 3.06

Measurements of Water Solubility at 20 °C

Sample Number	Time (Days)		Concentration (mg/L)		Mean Concentration (mg/L)	pH
	Held at 20 °C	Equilibrated at 20 °C
1, 2	2	5	691.8	811.6	751.7	3.02	3.03
3, 4	2	6	661.1	860.6	760.9	2.82	2.78
5, 6	2	7	755.8	881.8	818.8	2.86	2.79
Mean			777.1 mg/L

 

Sample Number	Time (Days)		Concentration (mg/L)		Mean Concentration (mg/L)	pH
	Held at 30 °C	Equilibrated at 20 °C
7, 8	2	5	872.1	913.7	892.9	3.06	3.05
9, 10	2	6	910.8	897.1	904.0	2.80	2.80
11, 12	2	7	1035.1	1011.2	1023.2	2.82	2.78
Mean			940.0 mg/L

 

Water solubility* = 858.6 ± 113.6 mg/L.

(C of V = 13.2 %)

* Determined as overall (pooled) mean of all tests.

Conclusions:

Under the conditions of the study the water solubility of the test material was found to be 858.6 ± 113.6 mg/L at 20 °C.

Executive summary:

The water solubility of the test material was assessed according to OECD Method 105, EEC Method A6 and EPA FIFRA Subdivision D § 63-8 and in compliance with GLP using the flask method.

The preliminary test samples were sonicated for 1 hour prior to equilibration at 20 °C for 24 hours. All the test material appeared to have dissolved in the first three samples, but some remained undissolved in the last sample, indicating a solubility between 600 and 1 000 mg/L. Consequently, the solubility was determined by the flask shaking method.

Four Pyrex bottles, each containing more than 200 mg of the test material and 200 mL of distilled water, were purged with nitrogen and sealed. The samples were sonicated then two bottles were shaken at 20 °C, and the other two at 30 °C for 48 hours before being transferred to equilibrate at 20 °C. After a further 5, 6 and 7 days, aliquots of the samples were filtered through 0.2 µm Millipore filters.  An aliquot (1 mL) of each filtrate was separately diluted to volume (25 mL) with mobile phase and the concentration of the test material in these solutions determined by HPLC/UV analysis.

Under the conditions of the study the water solubility of the test material was found to be 858.6 ± 113.6 mg/L at 20 °C.

Reference 4

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 April to 20 May 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

12 May 1981

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

December 1992

Deviations:

no

GLP compliance:

yes

Type of method:

flask method

Key result

Water solubility:

0.86 g/L

Conc. based on:

test mat.

Incubation duration:

>= 24 - <= 72 h

Temp.:

20 °C

pH:

3.1

Details on results:

The chromatograms of the pretreated water samples were comparable with the chromatograms of the standard dilutions. The chromatograms of the pretreated blank water sample did not show any peak with the same retention as the test material.

Preliminary Tests
First, the test material was stirred together with a 0.05 M buffer of pH 5, 7 or 9. However, after the stirring period it appeared that the pH of the test material had dropped significantly.
Apparently, the buffer capacity was too low. Therefore, the test was repeated using higher buffer concentrations (0.5 M). Again, the pH had dropped significantly after the stirring period, so the buffer capacity was still too small.
Finally, NaOH was added to the test material/ 0.5 M buffer mixtures until a pH of 4.9, 6.4 and 8.9, respectively was reached. This resulted in very high water solubilities at higher pH values.
The pH-dependency of the water solubility is very high in the pH range 3 - 7, indicating that the test material has a pKa value around 5.
Because of the very high water solubility, especially at higher pH-values, it is not possible to use a buffer of adequate strength to keep the solution at a constant pH-value.
Therefore, the main study was performed in double distilled water.
No significant differences were observed between the concentrations analysed after the second and third centrifugation step of preliminary tests 1 and 2.

Main Study
No significant differences were observed between the concentrations analysed after the third and fourth centrifugation step.
The 24, 48 and 72 hours measurements were in agreement. Therefore, the water solubility of the test material was calculated as the mean value of all measurements.

Results of the Water Solubility Test During the Preliminary Tests

Test System	Water Solubility (g/L)	pH
0.05 M buffer pH 5	1.51	3.23
0.05 M buffer pH 7	6.67	4.02
0.05 M buffer pH 9	4.86	3.83
0.05 M buffer pH 5	5.01	4.12
0.05 M buffer pH 7	43.65	4.92
0.05 M buffer pH 9	37.23	4.72
0.05 M buffer pH 5*	60.89	4.91
0.05 M buffer pH 7*	>331**	6.44
0.05 M buffer pH 9*	>230**	8.86

* Adjusted with additional NaOH.

** No correction was made for the mass fraction.

 

Results of the Water Solubility of The Test Material at 20.0 ± 1.0 °C. 

Stirring Time (hours)	Concentrations Analysed (g/L)*	Mean Concentration (g/L)	pH**
24	0.84 / 0.84†	0.84	3.1 / 3.1†
48	0.87 / 0.86†	0.87	3.1 / 3.1†
72	0.89 / 0.86†	0.88	3.1 / 3.1†
	Mean:	0.86

* Mean value or duplicate analysis.

** pH values or the 1:1 (v/v) diluted water samples with 0.01 H NaCl.

† Duplicate samples.

Conclusions:

Under the conditions of the study the water solubility of the test material is 0.86 g/L (pH 3.1) at 20.0 ± 1.0 °C. The pH-dependency of the water solubility is very high.

Executive summary:

The water solubility of the test material was assessed according to OECD Test Guideline 105 and in compliance with GLP using a flask method.

During the preliminary test, the water solubility of the test material was determined to be> 10^- 2 g/L. Therefore, the flask method was used for subsequent performance of the main study.

An amount of 0.6 - 0.7 g of the test material was weighed into each of three Erlenmeyer flasks. To each flask, 25 mL double distilled water was added. The flasks were securely closed and placed on a magnetic stirring device in a thermostatically controlled waterbath at 30 °C. The content of each flask was stirred for 24, 48 or 72 hours.

After the stirring periods, the flasks were removed from the waterbath and re-equilibrated for 24 hours at 20.0 ± 1.0 °C, with occasional agitation.

The concentration of the test material was determined using a High Performance Liquid Chromatographic method.

No significant differences were observed between the concentrations analysed after the third and fourth centrifugation step.

The 24, 48 and 72 hours measurements were in agreement. Therefore, the water solubility of the test material was calculated as the mean value of all measurements. The pH-dependency of the water solubility is very high.

Under the conditions of the study the water solubility of the test material is 0.86 g/L (pH 3.1) at 20.0 ± 1.0 °C.

Description of key information

Pawliczek (1987)

Under the conditions of the study, the solubility data of the test material at 20 °C was 860 mg/L dissolved in bidistilled water and 780 mg/L dissolve in water adjusted on an average of pH 3.

Comb (2000b)

Under the conditions of the study, the solubility of the test material was found to be 880 mg/L in purified water, 6.65 g/L in pH 4 buffer solution, greater than 250 g/L in pH 7 buffer solution, and greater than 250 g/L in pH 10 buffer solution.

Leeyen (1994)

Under the conditions of the study the water solubility of the test material is 0.86 g/L (pH 3.1) at 20.0 ± 1.0 °C.  The pH-dependency of the water solubility is very high.

O'Connor (1990)

Under the conditions of the study the water solubility of the test material was found to be 858.6 ± 113.6 mg/Lat 20 °C.

Key value for chemical safety assessment

Water solubility:

880 mg/L

at the temperature of:

20 °C

Additional information

Pawliczek (1987)

The water solubility of the test material was assessed according to guideline CIPAC Method 'MT 157/2 using a flask method and in compliance with GLP. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The test material was added in excess to the water and stirred intensively for half an hour, in one preparation at 10 °C above the test temperature, in another at 10 °C below the test temperature. Then in both preparations the test temperature was adjusted and stirring continued. Beginning from half an hour after the adjustment of the test temperature of 20 °C, samples were drawn from both preparations at various time intervals. The samples consisting of active ingredient suspensions were cleared from solid particles by pressure filtration using the apparatus Satorius SM 16 249 and a 0.2 µ polytetrafluorethylene membrane filter. The resulting clear solutions were analysed using the HPLC analytical method. Determination of the solubility in water adjusted to pH 3, measurement in hydrochloric solution of pH 3 and determination of the solubility in the alkaline range were also assessed.

Under the conditions of the study, the solubility data of the test material at 20 °C was 860 mg/L dissolved in bidistilled water and 780 mg/L dissolve in water adjusted on an average of pH 3. In the alkaline range (pH >9), the test material forms salts. Aqueous solutions containing more than 50 % of  the test material as sodium salts, did not show a tendency to crystallisation.

Comb (2000b)

The water solubility of the test material was assessed according to OECD Test Guideline 105 and EU Method A.6. and in compliance with GLP using a flask method. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Samples of the test material (pure grade) were weighed into separate Wheaton vials. The appropriate solvent (30 mL) was added to the flasks, which were purged with nitrogen, sealed and mixed at 30 °C for 1, 2 and 3 days (it was necessary to adjust the pH 4 samples with a few drops of 1M sodium hydroxide to the intended pH value at the start of the tests). On each occasion duplicate vials were transferred to equilibrate at 20 °C for 24 hours. The samples were then filtered through Whatman filter papers, and a subsample (1 mL) of each filtrate was diluted to volume (15 mL for the samples in purified water, and 50 mL for the samples in pH 4 buffer) with mobile phase for analysis by high performance liquid chromatography (HPLC).

The detector calibration was found to be linear over the range 0 to 216 mg/L of standard solutions in mobile phase with a regression coefficient of 1.0000

No peaks were observed in the chromatograms of the blank solutions indicating that the analytical method was free from interference.

Under the conditions of the study, the solubility of the test material was found to be 880 mg/L in purified water, 6.65 g/L in pH 4 buffer solution, greater than 250 g/L in pH 7 buffer solution, and greater than 250 g/L in pH 10 buffer solution.

Leeyen (1994)

The water solubility of the test material was assessed according to OECD Test Guideline 105 and in compliance with GLP using a flask method. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

During the preliminary test, the water solubility of the test material was determined to be> 10^-2 g/L. Therefore, the flask method was used for subsequent performance of the main study.

An amount of 0.6 - 0.7 g of the test material was weighed into each of three Erlenmeyer flasks. To each flask, 25 mL double distilled water was added. The flasks were securely closed and placed on a magnetic stirring device in a thermostatically controlled waterbath at 30 °C. The content of each flask was stirred for 24, 48 or 72 hours.

After the stirring periods, the flasks were removed from the waterbath and re-equilibrated for 24 hours at 20.0 ± 1.0 °C, with occasional agitation.

The concentration of the test material was determined using a High Performance Liquid Chromatographic method.

No significant differences were observed between the concentrations analysed after the third and fourth centrifugation step.

The 24, 48 and 72 hours measurements were in agreement. Therefore, the water solubility of the test material was calculated as the mean value of all measurements. The pH-dependency of the water solubility is very high.

Under the conditions of the study the water solubility of the test material is 0.86 g/L (pH 3.1) at 20.0 ± 1.0 °C.

O'Connor (1990)

The water solubility of the test material was assessed according to OECD Method 105, EEC Method A6 and EPA FIFRA Subdivision D § 63-8 and in compliance with GLP using the flask method. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The preliminary test samples were sonicated for 1 hour prior to equilibration at 20 °C for 24 hours. All the test material appeared to have dissolved in the first three samples, but some remained undissolved in the last sample, indicating a solubility between 600 and 1 000 mg/L. Consequently, the solubility was determined by the flask shaking method.

Four Pyrex bottles, each containing more than 200 mg of the test material and 200 mL of distilled water, were purged with nitrogen and sealed. The samples were sonicated then two bottles were shaken at 20 °C, and the other two at 30 °C for 48 hours before being transferred to equilibrate at 20 °C. After a further 5, 6 and 7 days, aliquots of the samples were filtered through 0.2 µm Millipore filters.  An aliquot (1 mL) of each filtrate was separately diluted to volume (25 mL) with mobile phase and the concentration of the test material in these solutions determined by HPLC/UV analysis.

Under the conditions of the study the water solubility of the test material was found to be 858.6 ± 113.6 mg/L at 20 °C.