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phototransformation in air
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
no guideline available
Principles of method if other than guideline:
Indirect photolysis with *OH radical
GLP compliance:

Test material

Specific details on test material used for the study:
- Name of test material (as cited in study report): L-21343

Study design

Light source:
other: Mercury-Xenon lamp
Details on light source:
- Lamp: Oriel Instruments UV Lamp, Model 66921 equipped with a 480 W Mercury Xenon bulb
- Emission wavelength spectrum: See Figure 1
- Filters used and their purpose: Manufacturer specifies a transmission range of 200-2500 nm for lamp window. No additional filtration. Some attenuation of IR is expected at quartz window of gas cell.
Details on test conditions:
The atmospheric lifetime of Novec 7700 was determined with respect to reaction with hydroxyl radical (OH). Hydroxyl radicals were produced by photolysis of ozone in the presence of water vapor. The results are based on the relative concentration of Novec 7700 and one of the reference compounds methane (CH4) or 1,1,1-trichloroethane, in the presence of the OH radical at 26-29 °C and at a pressure of approximately one atmosphere. The concentrations were monitored using continuous in-situ Fourier Transform Infrared (FTIR) spectroscopy according to EPA method 320.

The measurements were performed in a 10 meter (5.7L volume) heated FTIR gas cell equipped with a polished semiconductor-grade quartz window (Glass Tech Supplies, Inc.). An I-Series FTIR (Midac Corp.) was used for the analysis. The light source was placed above the gas cell and the UV radiation was introduced to the reagent gases through the quartz window. Novec 7700, methane, humidified nitrogen, dry nitrogen, and ozone were mixed using mass flow controllers. The gas mix was flowed through the FTIR cell. The experiment was conducted at approximately 1 atmosphere pressure. When the concentration of the gases reached the target value, the cell was sealed.

For the first part of the experiment, the quartz cell window was blocked with a shutter and the reagent gas concentrations were monitored for 12 to 36 minutes. After this initial period the lamp was switched on and the gases inside the cell were exposed to UV radiation. The decay of the gas concentrations in presence of UV light radiation was monitored for 37-70 minutes. The linear part of the degradation curve (ca. 40 minutes) was used to determine relative reaction rates. Atmospheric lifetime was then estimated for Novec 7700 by applying the relative reaction rates to the atmospheric lifetime of the appropriate reference substance. Three runs were done in total. Total test duration was 75-90 minutes.

During separate experiments, the sample gas mix was collected for subsequent analysis by GC-MS to ensure that only Novec 7700 was being measured and to screen for possible degradation products. Other degradation products were detected directly be FTIR.

Phototransformation of a specific degradation intermediate identified during the test was done as a second test. The same phototransformation chamber was used with illumination using an Oriel model 6251 UV lamp with a 75-W mercury-xenon bulb and 285-nm cutoff filter. No ozone was used, and acetaldehyde served as reference gas. Concentrations of Novec 7700 were ca. 0.6 ppmv, while concentrations of acetaldehyde were 27-37 ppmv. Duplicate runs were done. Total test durations were ca. 100 min or ca. 130 min.
Reference substance:
methane or 1,1,1-trichloroethane

Results and discussion

Dissipation half-life of parent compoundopen allclose all
Key result
3.9 yr
Test condition:
Average of three runs with methane or 1,1,1-trichloromethane as reference substance
0.9 d
Test condition:
Average of two runs for C10 diketone transformation product
Transformation products:
Identity of transformation productsopen allclose all
Reference substance name:
Inventory number:
InventoryMultipleMappingImpl [inventoryEntryValue=EC 206-534-2]
IUPAC name:
carbonyl difluoride
Carbonic difluoride
CAS number:
Molecular formula:
Molecular weight:
SMILES notation:
Reference substance name:
IUPAC name:
Molecular formula:
Molecular weight:
SMILES notation:

Any other information on results incl. tables

Concentrations of Novec 7700 and a reference substance were monitored in the absence of UV/Visible light to assess the background effect of dark reactions (adsorption to or reaction with the cell walls). Less than 1% losses were observed (Att. 1-3). Based on this result Novec 7700 does not react appreciably with either ozone or water vapor. On irradiation, linear declines in concentration of ozone, Novec 7700 and methane were observed for the first phase of illumination (Att. 1-3). Regression of this portion of the decay curves produced the following equations:

Run 1:

1,1,1-trichloroethane: C/Co = -0.00949 * time + 0.34381, R-sq = 0.997

Novec 7700: C/Co = -0.00953 * time + 0.30284, R-sq = 0.99

k,Novec 7700 / k,1,1,1-trichloroethane = -0.00953/-0.00949 = 1.00

lifetime, Novec 7700 = k,Novec 7700/k,1,1,1-trichloroethane * lifetime, 1,1,1-trichloroethane

Based on the accepted value of 1,1,1-trichloroethane lifetime, 5 years, the atmospheric lifetime of Novec 7700 is 5.0 years.

Run 2:

Methane: C/Co = -0.0135 * time + 0.4130, R-sq = 0.99

Novec 7700: C/Co = -0.00592 * time + 0.20287, R-sq = 0.99

k,Novec 7700/k,methane = -0.00592/-0.0135 = 2.28

lifetime, Novec 7700 = k,Novec 7700/k,methane * lifetime, methane

Based on the accepted value of methane lifetime, 12 years, the atmospheric lifetime is 5.3 years.

Run 3:

Methane: C/Co = -0.0110 * time + 0.1061, R-sq = 0.993

Novec 7700: C/Co = -0.00605* time + 0.06567, R-sq = 0.99

k,Novec 7700/k,methane = -0.00605/-0.0110 = 1.82

The corresponding atmospheric lifetime is 6.6 years.

The overall average atmospheric lifetime of Novec 7700 is 5.6 years, for an average half-life of 3.9 years.

Carbonyl difluoride was identified as a degradation product by FTIR. An unknown degradation product was detected as well. This was determined to be C10 diketone (1,1,1,2,4,4,5,5,7,8,8,8-dodecafluoro-2,7-bis(trifluoromethyl)octane-3,6-dione) by GC-MS compared to a known standard. The C10 diketone degradation intermediate was analyzed in duplicate direct photolysis runs v. acetaldehyde (Att. 4, 5):

Run 4:

Acetaldehyde: C/Co = -0.0019 * time + 0.0476, R-sq = 0.997

Novec 7700: C/Co = -0.0070 * time + 0.2409, R-sq = 0.9999

k,Novec 7700/k,acetaldehyde = -0.0070/-0.0019 = 3.68

Based on the accepted value of acetaldehyde lifetime, 5 days, the atmospheric lifetime is 1.4 days

Run 5:

Acetaldehyde: C/Co = -0.0017 * time + 0.0104, R-sq = 0.996

Novec 7700: C/Co = -0.0069 * time + 0.0397, R-sq = 0.9999

k,Novec 7700/k,acetaldehyde = -0.0069/-0.0017 = 4.06

The corresponding atmospheric lifetime is 1.2 days.

Acetaldehyde: C/Co = -0.0019 * time + 0.0476, R-sq = 0.997

Novec 7700: C/Co = -0.0070 * time + 0.2409, R-sq = 0.9999

k,Novec 7700/k,acetaldehyde = -0.0070/-0.0019 = 2.28

The overall average atmospheric lifetime of the C10 diketone intermediate degradation product is 1.3 days, for an average half-life of 0.9 days. Carbonyl difluoride was detected as transformation product of the C10 diketone as well. Carbonyl difluoride and trifluoroacetyl fluoride have very similar infrared spectra. While not specified in the study report, it is likely that trifluoroacetyl fluoride was also produced during both phototransformation experiments owing to branching in the diketone structure.

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
The half-life of Novec 7700 by indirect photolysis in the air is 3.9 years. A ketone intermediate is formed which has a half life of 0.9 days by direct photolysis.
Executive summary:

The atmospheric lifetime of Novec 7700 with respect to *OH was determined using methane or 1,1,1-trichloroethane as reference substance in a 10-m FTIR gas cell. Hydroxyl radical was produced by irradiation of ozone in the presence of water vapor. Temperature was 26-29 °C, and pressure was brought to approximately 1 atmosphere with nitrogen. Progress of the reaction was monitored by FTIR spectroscopy according to EPA method 320. On irradiation, losses of ozone, reference substance, and Novec 7700 were linear for the first phase of the reaction. Regression of the linear portion of the curves was used obtain a rate ratio (k, Novec 7700 / k,reference) for each run. Based on the accepted atmospheric lifetime for the reference substances (1,1,1-trichloroethane, 5 years; methane, 12 years), the atmospheric lifetime of Novec 7700 with respect to *OH is 5.6 years. Carbonyl difluoride was detected as a degradation product. An intermediate degradation product was identified as 1,1,1,2,4,4,5,5,7,8,8,8-dodecafluoro-2,7-bis(trifluoromethyl)octane-3,6-dione (C10 diketone) by GC-MS vs. a known sample. This intermediate was examined via direct phototransformation in the same test chamber but without ozone as a *OH source. The atmospheric lifetime of the C10 diketone was 1.3 days as compared to acetaldehyde (accepted lifetime, 5 days). Carbonyl difluoride was also detected as phototransformation product of this intermediate. While not specified in the study report, it is likely that trifluoroacetyl fluoride was also produced during phototransformation due to branching in the diketone structure.

The study followed sound scientific principles. The study overall was not conducted to GLP criteria. Composition of the reaction mixture is not specified in the report, however the relative reaction rate calculation mitigates the need for this detail. The study assumes phototransformation solely due to hydroxyl radical and does not take direct phototransformation into account. However, the methods described are adequate to obtain the measured result. Therefore, this study is classified as reliable with restrictions. It is suitable for Risk Assessment, Classification & Labeling, and PBT Analysis