reaction mass of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-2H -isothiazol-3-one

Hydrolysis

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Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

No OECD screening test was performed, definitive test was directly initiated. SOPs for HPLC, LSC, BFD and Ambis scanner may not have described the schedule or methods of calibration. Equipment maintenance not always documented as non-/routine.

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-1 (Hydrolysis)

Deviations:

yes

Remarks:

Sterile agar plates for solution sterility determination prepared in a non-GLP microbiology laboratory. Some synthetic standards for chromatography not completely characterized by GLP regulations.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Test material form:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Rohm and Haas, Batch No. 724.0209 (1993 study) and 902.01 (1998 study)

RADIOLABELLING INFORMATION (if applicable)
- Radiochemical purity: 97.4 % (1993 study), 97.73 % (1998 study)
- Specific activity: 31.6 mCi/g (1993 study), 41.0 mCi/g (1998 study)
- Locations of the label: 14C label was in the 4 and 5 positions

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Refrigerated
- Stability under test conditions:
- Solubility and stability of the test substance in the solvent/vehicle: Soluble and stable
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Dissolution in water
- Final preparation of a solid: 2.2 mg (70 µCi) 14C-CMIT in 4 mL water

Radiolabelling:

yes

Study design

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
Reference 1
pH 5: Days 0, 3, 10, 18, 23, and 30
pH 7: Days 0, 3, 10, 18, 23, and 30
pH 9: Days 0, 1, 3, 7, 10, 18, and 30
Reference 2
pH 9: Days 0, 3, 7, 15, 21, and 42
- Sampling method: Vials were prepared for each sampling interval.
- Sampling intervals/times for pH measurements:
Reference 1
The initial pH and the pH on Day 30 pH were measured with a pH meter. At the intermediate sampling interval the pH was measured using pH paper.
Reference 2
The prepared buffer solution was measured using a pH meter while the pH of the individual samples was performed using pH paper.
- Sampling intervals/times for sterility check: All sampling intervals.
- Sample storage conditions before analysis: Usually samples were chromatographed on the collection day. In a few cases the samples were stored prior to analysis. The longest period between sampling and analysis was one day.

Buffers:

- pH: 5
- Type and final molarity of buffer: 0.01 M Acetate
- Composition of buffer: 146 mL of 0.1M acetic acid plus 100 mL of 0.1M NaOH made up to 1000 mL with distilled water

- pH: 7
- Type and final molarity of buffer: 0.01 M Phosphate
- Composition of buffer: 22.4 mL of 0.1M KH2PO4 plus 25.8 mL of 0.1M Na2HPO4 made up to 1000 mL with distilled water

- pH: 9
- Type and final molarity of buffer: 0.01 M Sodium Tetraborate-HCl
- Composition of buffer:
Reference 1: 46 mL of 0.04M HCl plus 500 mL of 0.01M Na2B407•10H2O made up to 1000 mL with distilled water
Reference 2: 23 mL of 0.04M HCL plus 250 mL of 0.01M Na2B407•10H2O made up to 500 mL with distilled water

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 8 mL sterile pyrex tubes
- Sterilisation method: Filtration through a Falcon or Corning 0.22 µm filter
- Lighting: dark
- Measures taken to avoid photolytic effects: placed into a dark incubator
- Measures to exclude oxygen: n/a
- Details on test procedure for unstable compounds: n/a
- Is there any indication of the test material adsorbing to the walls of the test apparatus? Not described
TEST MEDIUM
- Volume used/treatment: 5 mL
- Kind and purity of water: Water from Barnsted Nano Pure II system
- Preparation of test medium: n/a
- Renewal of test solution: No
- Identity and concentration of co-solvent: Reference 2: methanol (0.3%)
OTHER TEST CONDITIONS
- Adjustment of pH: dropwise addition of a NaOH solution
- Dissolved oxygen: n/a

Duration of test

Duration of test 1

Duration:

42 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

478 µg/L

Duration of test 2

Duration:

42 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

1.1 µg/L

Duration of test 3

Duration:

30 d

pH:

5

Temp.:

25 °C

Initial conc. measured:

11.4 µg/L

Duration of test 4

Duration:

30 d

pH:

7

Temp.:

25 °C

Initial conc. measured:

11 µg/L

Duration of test 5

Duration:

30 d

pH:

9

Temp.:

25 °C

Initial conc. measured:

10.9 µg/L

Number of replicates:

2 replicates per sample interval

Positive controls:

no

Negative controls:

no

Statistical methods:

Not described

Results and discussion

Preliminary study:

Reference 1: a preliminary test was employed to estimate the kinetics and develop and refine analytical techniques and methods for the definitive study. Initially a solubility examination was performed by dosing the sterile pH 5, 7, and 9 buffers at a nominal CMIT concentration of 8.4 ppm. Results confirmed that CMIT remained in solution over a 48 hour interval.
A pilot application of 8.4 ppm (nominal) was conducted in the three buffer solutions. Single samples were removed between 1 and 7 days and parent determined chromatographically. These results assisted in determining the sampling intervals in the definitive study.

Reference 2: No preliminary test was necessary.

Transformation products:

yes

Identity of transformation products

No.:

#1

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

Reference 1
- Formation and decline of each transformation product during test: parent compound is very stable at pH 5 and 7. The sum of all the observed degradates at pH 5 and 7 was 6.1 % of the applied activity or less. At pH 9, CMIT hydrolyzes to two detectable degradates. Degradate A ranged from 3.3 % of applied (Day 0) to 39.3 % (Day 30) whereas Degradate B ranged from 0 % on Day 0 to 9.8 % on Day 30. As discussed below, Degradate A was identified as N-methyl malonamic acid.
- Pathways for transformation: See below.

Reference 2
- Formation and decline of each transformation product during test: The percent parent decreased from 100 % on Day 0 to about 20 % on Day 42. N-methyl malonamic acid was the major hydrolytic product observed, first detected at day 7 and constituting about 65 % of 14C applied after 42 days. Other 6 compounds amounted individually to < 6% of 14C applied after 42 days.
- Pathways for transformation: The ring opening yields one major hydrolytic degradate at greater than 10 %, which was definitively identified by mass spectrometry as N-methyl malonamic acid.

Total recovery of test substance (in %)

Total recovery of test substance (in %) 1

% Recovery:

101.3

St. dev.:

5.9

pH:

5

Temp.:

25 °C

Duration:

30 d

Total recovery of test substance (in %) 2

% Recovery:

103.2

St. dev.:

2.4

pH:

7

Temp.:

25 °C

Duration:

30 d

Total recovery of test substance (in %) 3

% Recovery:

104.6

St. dev.:

2.6

pH:

9

Temp.:

25 °C

Duration:

30 d

Total recovery of test substance (in %) 4

% Recovery:

99.96

St. dev.:

1.25

pH:

9

Temp.:

25 °C

Duration:

42 d

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

Key result

pH:

5

Temp.:

25 °C

Hydrolysis rate constant:

< 0.001 h-1

DT50:

> 60 d

Type:

not specified

Remarks on result:

other: R2 = 0.345

Dissipation DT50 of parent compound 2

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

< 0.001 h-1

DT50:

> 60 d

Type:

not specified

Remarks on result:

other: R2 = 0.064

Dissipation DT50 of parent compound 3

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.031 h-1

DT50:

22 d

Type:

not specified

Remarks on result:

other: Reference 1; R2 = 0.921

Dissipation DT50 of parent compound 4

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.041 h-1

DT50:

16.9 d

Type:

not specified

Remarks on result:

other: Reference 2; R2 = 0.974

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS
At pH9:
Reference 1
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 36.6% of the applied amount after 30 days
- Range of maximum concentrations in % of the applied amount at end of study period: 36.6% of the applied amount
Reference 2
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 61.56 to 67.40% of the applied amount after 42 days
- Range of maximum concentrations in % of the applied amount at end of study period: 61.56 to 67.40% of the applied amount

MINOR TRANSFORMATION PRODUCTS
Maximum concentrations in % of the applied amount
Reference 1
- at pH5: Total 2.7%
- at pH7: Total 3.9%
- at pH9: Total 9.8%
Reference 2
- at pH9: Peak 2: 0-4.19%; Peak: 3 0-5.74%; Peak 4: 4.46-8.60%; Peak 5: 0%; Peak 6: 0-3.63%; Peak 8: 0-5.68%.

MINERALISATION (distinguish between dark and irradiated samples)
- % of applied radioactivity present as CO2 at end of study: n/a

INDICATION OF UNSTABLE TRANSFORMATION PRODUCTS: n/a

VOLATILIZATION (at end of study)
n/a

UNIDENTIFIED RADIOACTIVITY (at end of study)
Reference 1
- at pH5: 2.7%
- at pH7: 3.9%
- at pH9: 9.8%

Reference 2
- at pH9: 16.15%

PATHWAYS OF HYDROLYSIS
- Description of pathways: The ring opening yields one major hydrolytic degradate at greater than 10 %, which was definitively identified by mass spectrometry as N-methyl malonamic acid.
- Figures of chemical structures attached: No

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

CMIT is stable to hydrolysis at pH5 and 7. At pH 9 however, CMIT hydrolyses rapidly with an extrapolated half-life of 22 days (Reference 1) and 16.9 days (Reference 2). The ring opening yields one major hydrolytic degradate at greater than 10 %, which was definitively identified by mass spectrometry as N-methyl malonamic acid.

Executive summary:

Reference 1: Sterile pH 5, 7, and 9 buffers were prepared and dosed at nominal 10 ppm with¹⁴C-CMIT. Buffered-¹⁴C solutions were incubated in the dark at 25°C and periodically replicate samples were removed, radioassayed, and parent quantitated using HPLC. Sampling intervals were determined from preliminary experiments.

 

Reference 2: Sterile pH 9 buffer was prepared and dosed at 1.10 ppm with¹⁴C-CMIT. Buffered¹⁴C solutions were incubated in the dark at 25°C and periodically replicate samples were removed and total¹⁴C-activity quantitated by radioassayed. One replicate was chromatographed the day of sampling and the other was stored frozen for about 4 weeks and then chromatographed (HPLC). To assist in identification of degradates, buffer solutions comprising¹²C and¹⁴C CMIT were dosed at 478 ppm. Degradates were isolated from the low and high dose CMIT solutions by HPLC and identified using LC-ESI-MS

Guidelines followed were US EPA FIFRA 161-1. The study was conducted in compliance with GLP guidelines.

These studies fulfil the requirement for determining the effect of aqueous hydrolysis on the fate of CMIT in the environment. CMIT is stable to hydrolysis at pH5 and 7. At pH 9 however, CMIT hydrolyses rapidly with an extrapolated half-life of 22 days (Reference 1) and 16.9 days (Reference 2). The ring opening yields one major hydrolytic degradate at greater than 10 %, which was definitively identified by mass spectrometry as N-methyl malonamic acid.