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Physical & Chemical properties

Stability: thermal, sunlight, metals

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Endpoint:
stability: thermal, sunlight, metals, other
Remarks:
Migrated from section 'Stability: thermal, sunlight, metals'
Type of information:
experimental study
Adequacy of study:
key study
Study period:
February - July 1995
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was not conducted according to guidelines but was conducted according to GLPs and the report contains sufficient data for interpretation of study results.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1995
Report Date:
1995

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
other: ASTM Method E-537-86 for thermal stability
Deviations:
not specified
Qualifier:
no guideline followed
Guideline:
other: for stability to sunlight
Deviations:
not specified
Qualifier:
no guideline followed
Guideline:
other: for stability around metal
Deviations:
not specified
Principles of method if other than guideline:
For stability to sunlight, the test material was kept in the dark and exposed to artificial sunlight for 72 hours. Samples were analyzed by HPLC.

For stability around metal, the test material was analyzed in the presence of mild steel coupons.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: solid
Details on test material:
All Series 63 characterizations of Kordek 573T Industrial Microbicide were done using the Technical Grade Active Ingredient (TGAI). The test material consisted of >95% 2-methyl-4-isothiazol-3-one. Impurities ranged from 0.1 to 1.0% and total less than 5.0%.

Results and discussion

For thermal stability study

Test substance thermally stable:
yes
Operating temperature
Operating temp.:
< 160 °C
Remarks on result:
other: At temperatures above 160C, major exothermic decomposition can be observed with extrapolated onset temperatures of between 222C and 226C and peak temperatures between 235C and 238C.
Transformation products:
yes

For study on stability to sunlight

Test substance stable to sunlight:
yes

For study on stability to metals

Test substance stable to metals / metal ions:
no

Any other information on results incl. tables

Thermal stability

None of the samples exhibited evidence of significant exothermic behavior at temperatures before 160C. At temperatures above 160C, major exothermic decomposition can be observed with extrapolated onset temperatures of between 222C and 226C and peak temperatures between 235C and 238C.

Thermal Stability by TGA for Kordek 573T

      Onsets TC
  Lot #  "true"  extrapolated    Peak TC
1026 -DSC   161  222  235
 1028 -DSC  172  226  240
 1029 -DSC  160  223  237
 1031 -DSC  160 (142)*  222  237

* Base line noise made the exact determination of the "true onset" difficult.

Sunlight Exposure

The F-test for differences among the seven means is significant (F = 16.47, p = 0.0085). The "0 hr/no sun" (control), "72 hr/sun" and "72 hr/no sun" means are not statistically different from each other, but they are different from the other means. The other means (24hr/sun, 24 hr/no sun, 48 hr/sun, 48 hr/no sun) are not statistically different from each other. There may be some other factor that is causing these significant differences. The statistical differences found do not follow the patterns one would expect if exposure and/or storage time degraded percent active ingredient. It is clearly not the exposure to sunlight since exposed and non-exposed samples stored for the same length of time are not statistically different. It is also not do to the length of exposure since the 72 hours samples are not statistically different than the control. The differences may be due to day-to-day testing variation or the sampling of the lot of product.

The regression analysis shows there is no statistically significant trend in the exposure time for both the sunlight exposed or not exposed samples. There is no statistical evidence to show an effect of exposure time on the percent active ingredient of the tested samples.

Stability to Sunlight

 Sample ID  Exposure Time  Foil Covered  Average PPM RH-573 (Std Dev)
 R95 -338 -1  24 hours  yes  97.14 (0.235)
 R95 -338 -20  24 hours  yes  97.04 (0.142)
 R95 -338 - 21  24 hours  no  97.34 (0.174)
 R95 -338 -22  24 hours  no  97.22 (0.100)
 R95 -338 -23  48 hours  yes  97.46 (0.244)
 R95 -338 -24  48 hours  yes  97.08 (0.180)
 R95 -338 -25  48 hours  no  97.13 (0.239)
 R95 -338 -26  48 hours  no  97.55 (0.162)
 R95 -338 -27  72 hours  yes  98.75 (0.103)
 R95 -338 -28  72 hours  yes  98.02 (0.081)
 R95 -338 -29  72 hours  no  98.16 (0.571)
 R95 - 338 -30  72 hours  no  97.98 (0.163)
 R95 - 338 -31  no exposure  --  98.80 (0.094)

Stability to metal

The F-test for differences among the means is significant (F=23.78 p=0.0404). The no metal and control least square means (96.21 and 95.98%AI) are not statistically different, but both differ significantly (p-value<0.05) from the metal mean (93.14%AI). The presence of metal does significantly reduce the percent active ingredient of the Kordek 573T samples.

Stability in the presence of metal

      No Heat, No Metal     Heat (50C), No Metal     Heat (50C) + Metal
 Lot No.  Mean  Grand Mean  Mean  Grand Mean  Mean  Grand Mean
 1029  96.7  ---  97.2  ---  94.6  ---
 1031  95.3  ---  95.3  ---  91.7  ---
 Lots combined  ---  96.0  ---  96.3  ---  93.2

Note Numbers are slightly different in this Summary Table from numbers in text.

Applicant's summary and conclusion

Conclusions:
At temperatures above 160C, major exothermic decomposition can be observed with extrapolated onset temperatures of between 222C and 226C and peak temperatures between 235C and 238C. The test material was stable to sunlight but was not stable in the presence of metal at 50C for one week.
Executive summary:

Stability in the presence of heat, sunlight and metal was determined. At temperatures above 160C, major exothermic decomposition can be observed with extrapolated onset temperatures of between 222C and 226C and peak temperatures between 235C and 238C. The test material was stable to sunlight but was not stable in the presence of metal at 50C for one week.