Paraquat-dichloride

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March 1985 to June 1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

Tested at pH 5, 7 and 9 (should be 4,7 and 9 according to the guideline) and at temperatures of 25 and 40°C (should be 50°C according to the guideline)

GLP compliance:

yes

Radiolabelling:

yes

Remarks:

14C

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: 0, 2, 8, 16 and 30 days
- Sampling method: Duplicate flasks were taken for analysis from each set of buffer solutions at both temperatures.
- Sampling intervals/times for pH measurements: The pH values of the buffer solutions were measured at ambient temperature at time zero and after 30 days incubation and at 40°C.
- Sample storage conditions before analysis: The samples were stored at -20°C prior to analysis.

Buffers:

- pH 5: 0.1 M potassium hydrogen phthalate and 0.05 M sodium hydroxide in a 1:1 ratio
- pH 7: 0.071 M potassium dihydrogen orthophosphate and 0.05 M disodium hydrogen phosphate in a 1:1 ratio
- pH 9: 0.1 M potassium chloride in 0.1 M boric acid and 0.05 M sodium hydroxide in a 1:1 ratio

- Measured pH day 0: 5.00, 6.87 and 9.07
- Measured pH day 30: 5.01, 6.86 and 9.08
- pH at 40 °C: 5.09, 6.81 and 8.95

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 50 mL quickfit stoppered conical flasks were incubated in a shaking water bath.
- Sterilisation method: To ensure sterile conditions for the hydrolysis, buffer solutions and all the glassware used was placed in an autoclave overnight (Maximum temperature 121°C at 15 psi pressure). Substance stock solutions were sterilized by passing through a bacteriological aqueous filter (0.22μm). All transfer of solutions was carried out in a laminar flow hood.
- Measures taken to avoid photolytic effects: The water baths were tightly covered to exclude light.

TEST MEDIUM
- Volume used: 0.7 mL of radiolabelled stock solution, 2.55 mL of non labelled stock solution and buffer to give a final volume of 30mL.

Duration:

30 d

pH:

5

Temp.:

25 °C

Initial conc. measured:

>= 89.3 - <= 90.2 mg/L

Duration:

30 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

>= 95.9 - <= 98.1 mg/L

Duration:

30 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

>= 82.1 - <= 85.6 mg/L

Duration:

30 d

pH:

5

Temp.:

40 °C

Initial conc. measured:

>= 92.7 - <= 94.7 mg/L

Duration:

30 d

pH:

7

Temp.:

40 °C

Initial conc. measured:

>= 94.2 - <= 95.3 mg/L

Duration:

30 d

pH:

9

Temp.:

40 °C

Initial conc. measured:

>= 79.4 - <= 90.5 mg/L

Number of replicates:

Duplicates

Positive controls:

no

Negative controls:

no

Transformation products:

not measured

Details on hydrolysis and appearance of transformation product(s):

- Recovery of radioactivity: over the incubation period, at both temperatures and at all pH values there was no significant loss of radioactivity.
- Chromatographic analysis: samples taken after 2, 8, 16 and 30 days incubation showed that no significant breakdown had occurred.
- Details are provided in the 'any other information on results incl. tables' section

% Recovery:

> 100

pH:

5

Temp.:

25 °C

Duration:

30 d

% Recovery:

>= 98

pH:

5

Temp.:

40 °C

Duration:

30 d

% Recovery:

>= 97

pH:

7

Temp.:

25 °C

Duration:

30 d

% Recovery:

>= 96

pH:

7

Temp.:

40 °C

Duration:

30 d

% Recovery:

>= 87 - <= 99

pH:

9

Temp.:

25 °C

Duration:

30 d

% Recovery:

> 100

pH:

9

Temp.:

40 °C

Duration:

30 d

Key result

pH:

9

Temp.:

40 °C

Remarks on result:

not determinable

Remarks:

Substance is hydrolytically stable under the tested conditions

Key result

pH:

7

Temp.:

40 °C

Remarks on result:

not determinable

Remarks:

Substance is hydrolytically stable under the tested conditions

Key result

pH:

5

Temp.:

40 °C

Remarks on result:

not determinable

Remarks:

Substance is hydrolytically stable under the tested conditions

pH:

9

Temp.:

25 °C

Remarks on result:

not determinable

Remarks:

Substance is hydrolytically stable under the tested conditions

pH:

7

Temp.:

25 °C

Remarks on result:

not determinable

Remarks:

Substance is hydrolytically stable under the tested conditions

pH:

5

Temp.:

25 °C

Remarks on result:

not determinable

Remarks:

Substance is hydrolytically stable under the tested conditions

Details on results:

TEST CONDITIONS
At pH 5, 7 and 9:
- Over the incubation period, at both temperatures and at all pH values there was no significant loss of radioactivity.
- Chromatographic analysis (TLC and linear scanning of the chromatoplates) of the samples taken after 2, 8, 16 and 30 days incubation showed that no significant breakdown of the substance had occurred.
- Detailed results of the chromatographic analysis of the 30 day samples are provided in the 'any other information on results incl. tables' section.

Table: Mean percentage of radioactivity present as paraquat after day 0 and day 30

Sample interval	Temperature (°C)	Sample	pH 5	pH 7	pH 9
Day 0	25	A	97.5	97.8	95.5
Day 0	25	B	94.7	96.0	96.9
Day 0	40	A	95.3	96.6	96.8
Day 0	40	B	97.9	95.6	96.4
Day 30	25	A	96.3	94.7	97.5
Day 30	25	B	94.8	94.4	96.9
Day 30	40	A	96.2	97.2	93.0
Day 30	40	B	90.9	95.5	94.7

Validity criteria fulfilled:

yes

Conclusions:

The results from this study show that the test substance is stable to hydrolysis at temperatures up to 40°C at pH 5 to 9 for 30 days.

Executive summary:

The hydrolysis potential of the 14C radiolabelled test item was investigated in a study similar to OECD TG 111 and in compliance with GLP criteria. This study was performed at 25 and 40 °C for 30 days at pH values of 5, 7 and 9 in duplicate. All incubations were conducted under sterile and dark conditions. The degradation of the parent compound over a period of time was measured using both thin layer chromatography and high performance liquid chromatograph and recovery of radioactive content was determined with liquid scintillation counting. TLC and scintillation counting were performed after 2, 8, 16 and 30 days. Since no significant breakdown was observed detailed chromatographic analysis of the 30 day samples is only reported. The results show that over the incubation period, at both temperatures and at all pH values there was no significant loss of radioactivity. In addition, chromatographic analysis showed that no significant breakdown had occurred during the 30 day period. Therefore, the substance is considered to be hydrolytically stable.

Description of key information

The test substance is hydrolytically stable at pH values of 5, 7 and 9 at a temperature of 25 and 45 °C, OECD TG 111, Upton, 1985

Additional information

Method			Guideline / GLP	Comment	Reference
Temperature	pH	Duration
25 °C	5	30 d	OECD TG 111	The test item is hydrolytically stable at pH values of 5, 7 and 9 at temperature of 25 and 45 °C	Upton, 1985
25 °C	7	30 d
25 °C	9	30 d
40 °C	5	30 d
40 °C	7	30 d
40 °C	9	30 d