Pirimiphos-methyl

Boiling point

Link to relevant study record(s)

Reference

Endpoint:

boiling point

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 Sep 2014 to 31 Oct 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 103 (Boiling Point)

Version / remarks:

27 Jul 1995

Qualifier:

according to guideline

Guideline:

EU Method A.2 (Boiling Temperature)

Version / remarks:

30 May 2008

GLP compliance:

yes (incl. QA statement)

Type of method:

differential scanning calorimetry

Key result

Atm. press.:

>= 101 - <= 101.5 kPa

Decomposition:

yes

Decomp. temp.:

162 °C

RESULTS:

The test substance was determined to decompose from approximately 162 °C (435 K), at 101.0 to 101.5 kPa. Decomposition was observed both in air and under a nitrogen atmosphere. Therefore, due to thermal decomposition, the boiling point cannot be determined for this substance.

From comparison of the thermogram profiles obtained from samples analysed using pre-perforated crucible lids (which allow self-pressurisation up to the boiling temperature) and those using manually pierced crucible lids (i.e. an open system), it is possible to evaluate if an observed endotherm originates from a true boiling temperature for the test substance. However in this case, it was possible to conclude from the exothermic response and remaining residue found for determination 1 that the test substance underwent decomposition on heating, with no evidence of boiling. Due to the eruption of the decomposition products from the sample crucible, which had potential to compromise / damage the DSC sensor, all additional determinations were terminated at a lower final temperature of 245 °C. This had no impact on the integrity of the study since the temperature range remained sufficient to allow quantification of the decomposition temperature from the exotherm onset, and decomposition was also further supported visually by the discoloration of the test substance residue remaining on completion of each determination. Due to the low initial rate of enthalpy change during decomposition, the onset temperature could only be approximated. The use of manually pierced crucibles (an open system) also provided an opportunity to assess the stability of the test substance in air and in an inert atmosphere (nitrogen). Decomposition was observed both in air and under a nitrogen atmosphere, indicating the process was most likely thermal and not oxidative.

Table 1  Thermographic data – determination 1

Thermal Event	Interpretation	Temperature
		ºC	K
Approximate exotherm onset temperature.	Approximate decomposition onset temperature	187.79	461
Extrapolated exotherm onset temperature.	Extrapolated decomposition onset temperature	237.43	511

Table 2  Thermographic data – determination 2

Thermal Event	Interpretation	Temperature
		ºC	K
Approximate exotherm onset temperature.	Approximate decomposition onset temperature	178.71	452
Extrapolated exotherm onset temperature.	Extrapolated decomposition onset temperature	234.99	508

Table 3  Thermographic data – determination 3

Thermal Event	Interpretation	Temperature
		ºC	K
Approximate exotherm onset temperature.	Approximate decomposition onset temperature	178.33	451
Extrapolated exotherm onset temperature.	Extrapolated decomposition onset temperature	224.89	498

Table 4  Thermographic data – determination 4

Thermal Event	Interpretation	Temperature
		ºC	K
Approximate exotherm onset temperature.	Approximate decomposition onset temperature	162.10	435
Extrapolated exotherm onset temperature.	Extrapolated decomposition onset temperature	219.99	493

Table 5  Thermographic data – determination 5

Thermal Event	Interpretation	Temperature
		ºC	K
Approximate exotherm onset temperature.	Approximate decomposition onset temperature	166.03	439
Extrapolated exotherm onset temperature.	Extrapolated decomposition onset temperature	217.69	491

Conclusions:

Due to thermal decomposition starting at about 162 °C, the boiling point cannot be determined for this substance.

Executive summary:

The study was performed in accordance with OECD TG 103 and in compliance with GLP to evaluate the boiling temperature of the test substance. The test substance was determined to decompose from approximately 162 °C (435 K), at 101.0 to 101.5 kPa. Decomposition was observed both in air and under a nitrogen atmosphere. Therefore, due to thermal decomposition, the boiling point cannot be determined for this substance.

Description of key information

The test substance decomposes before boiling from approximately 162 °C (99.2% pure), OECD TG 103, DSC, O'Connor 2014.

Key value for chemical safety assessment

Temperature of decomposition (state purity):

162 °C

Additional information

Another study was performed to determine the boiling point of the test substance in technical material in accordance with OECD TG 102 and in compliance with GLP. Here the boiling point could also not be determined as significant decomposition was observed.