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Responses to EPA Review of Fluoropolymers Incineration ECA Final Study Report-Part 2

March 2, 2015

On July 12, 2013, Dr. Philip Taylor of the University of Dayton Research Institute (UDRI) responded 

to several questions sent via electronic mail on May 20, 2013 by Joe Avcin of EPA. Three areas or 

sub-areas of inquiry were deferred to a later date. Further work on these three items has been 

delayed primarily due to refocusing resources on completing and publishing a paper in 

Chemosphere on the Telomers ECA incineration study in 2014 and Dr. Taylor’s retirement from 

UDRI. The text below responds to each of the remaining three items. It is important to note that 

both Phase I and Phase II testing described in the Final Study Report were performed in accordance 

with the requirements of the Enforceable Consent Agreement (ECA) and TSCA GLPs as embodied in 

the EPA-approved Quality Assurance Project Plans (QAPPs). The project team established and 

executed a quality management system to assure conformance with the EPA-approved QAPPs and 

documented such conformance in the Final Study Report submitted October 30, 2009.

1. Area #3 – O-ring a source of F?

During Composite 2 incineration testing of the previously-completed fluorotelomer Phase II incineration study, 

unsteady oxygen and carbon dioxide exhaust concentrations, perhaps due to exhaust gas leaks, led to reactor 

system repairs. The repairs included replacing corroded stainless steel tubing and replacing the reactor exit-end 

silicone O-ring with a higher-temperature-rated perfluoroelastomer O-ring. This perfluoroelastomer O-ring 

remained in service during all fluoropolymer Phase II incineration testing. EPA would like to better understand if 

the observed fluoride ion concentrations in the impinger samples may be the result of the O-ring used in the 

reactor system as well as the combustion of the fluoropolymer composites.

The final report concludes that the fluoride ion concentration resulting from the experimental runs are due 

entirely to the combustion of the fluoropolymer composites. This conclusion was made with the following 

statement on page 16 and 17 of the final report:

“Fluoride ion analytical results for the pre-test steam cleanings (in contrast to pre-test thermal 

blanks) indicate that degradation of the perfluoroelastomer O-ring on the reactor exit is the 

primary source of fluoride ion in the impingers under post-run steam cleaning conditions. (These 

conditions include higher exit end fitting temperature and much higher exhaust gas water 

concentration than during experimental runs.) Hence, the fluoride ion results for the experimental 

runs correspond directly to the combustion of the fluoropolymer composites, independent of Oring degradation during steam cleaning.”

EPA finds a potential issue with using a perfluoroelastomer O-ring as a corrective action to repair a leak in the 

exhaust gas line and with concluding that its use had no effect on the results for experimental runs. The impinger 

results for the thermal blanks also contained a detectable concentration of fluoride ion ranging from 0.031 to 0.12 

mg/L (approximately ten- to twenty-times less than the combustion experimental run results). The contribution of 

fluoride ion during the thermal blank runs may also be a result of O-ring degradation. Therefore, EPA wants to 

know if it is possible that a portion of the fluoride ion present during the experimental runs may also be a result of 

O-ring degradation. 

In a related comment as part of Area #5, EPA also stated:

Further, the study did not subtract any estimate of baseline fluoride ion levels due to degradation of the O-ring.

EPA asks about (a) use of a perfluoroelastomer O-ring as a corrective action to repair an 

apparent leak in the reactor exhaust gas line and (b) the potential contribution of 

perfluoroelastomer O-ring degradation under experimental run (and thermal blank)

conditions to fluoride ion results for experimental run impinger samples.
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a.

As the Agency notes, repairs necessary to correct unsteady oxygen and carbon dioxide 

exhaust concentration during Phase II fluorotelomers incineration testing included 

replacing the reactor exit-end silicone O-ring with a perfluoroelastomer O-ring. These 

repairs were described in a July 22, 2008 Corrective Action Form (included in Appendix 1 

to the Fluorotelomers Final Study Report). As the run checklist T4 Nut readings for 

Fluorotelomer runs 4-6 and runs 1R-3R in Appendix 26 to the Fluorotelomers Final Study 

Report indicate, reactor exit fitting (T4 Nut) temperatures during Fluorotelomers Phase II 

combustion testing (especially steam cleaning) exceeded the maximum continuous service 

temperature of the exit-end silicone O-ring. The only commercially available O-ring 

material capable of such higher temperature service was and is perfluoroelastomer. Hence, 

the reactor exit O-ring was upgraded to a perfluoroelastomer O-ring (Kalrez® 7075) for 

the remainder of the Fluorotelomers study; see page 111 of Richard Striebich’s

Fluorotelomers Phase II notebook in Appendix 5 to the Fluorotelomers Final Study Report. 

Upgrading to a perfluoroelastomer O-ring was necessary to assure steady and 

representative oxygen and carbon dioxide monitoring and to keep the study on schedule to 

comply with the deadlines imposed by the Fluorotelomers incineration ECA. 

As the second July 22, 2008 Corrective Action Form in Appendix 1 to the Fluorotelomers 

Final Study Report indicates, additional testing was performed to evaluate the potential 

contribution of the exit end perfluoroelastomer O-rings to the impinger fluoride results. 

These additional tests were described in Appendix 29 to the Fluorotelomers Final Study 

Report and indicated that fluoride levels seen in Fluorotelomers study steam cleaning 

samples were due to perfluoroeleastomer O-ring degradation during steam cleaning. 

Analytical laboratory problems during analysis of the Fluorotelomers study samples 

prevented confident low-level quantitation of fluoride in the HPLC water used to fill the 

impingers prior to each run, preventing the study team from considering the contribution 

of the HPLC water to fluoride background during the Fluorotelomers study. 

In preparation of the Fluoropolymers incineration study, the reactor exit-end O-ring was 

upgraded from Kalrez® 7075 to Kalrez® 9100 to minimize the potential for 

perfluoroelastomer O-ring contribution to impinger fluoride levels; see October 7, 2009 

Corrective Action form by Richard Striebich (included in Appendix 1 to the Fluoropolymers 

Final Study Report). As noted in that Corrective Action form, the upgrade to 9100 was to 

assure less HF off-gassing at the reactor exit end fitting based on consultation with the 

perfluoroelastomer O-ring manufacturer. 

b.

The data presented for the series of pretest steam cleanings (prior to use of each new 

reactor tube) in the Fluoropolymers Final Study Report clearly show that fluoride ion 

results for steam cleaning samples (with higher fitting temperature and much higher 

exhaust gas water concentration than experimental runs) during the Fluoropolymers 

incineration study are attributable to the perfluoroelastomer O-ring on the exit-end of the 

reactor. However, the potential contribution of the O-ring to the experimental run and 

thermal blank impinger sample fluoride results is another matter.
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Section F.4.a(5) of the Fluoropolymers Final Study Report (p. 56) notes that the sources of 

background levels of fluoride ion in the thermal blank impinger samples were (1) the HPLC 

water used to fill the impingers prior to each run, (2) the synthetic air feed to the reactor 

system, and (3) potential degradation of the exit-end perfluoroelastomer O-ring. 

(1) Review of Richard Striebich’s Fluoropolymers Phase II notebook (Appendix 36 to the 

Fluoropolymers Final Study Report) indicates that Lot C28T002 water was used to fill 

impingers for runs 1, 2, and 3, that Lot D14T068 water was used to fill impingers for runs 

4, 5, 6, and 7, and that Lot D13U027 water began to be used to fill impingers at the 

beginning of run 8. (Review of the notebook pages does not show clear evidence of actual 

use of Lot F17U015 water to fill impingers in the test program.) Fluoride was measured in 

the HPLC water. Table 16 of the Fluoropolymers Final Study Report indicates that fluoride 

was not detected in Lots C28T002 and D14T068 and that Lots D13U027 and F17U015 

contained 0.037 mg/L and 0.043 mg/L of fluoride ion, respectively.

(2) While fluoride was likely present in commercially prepared synthetic air at the time of 

this work based on review of Wickbold Torch system blanks at the Total Fluorine analysis 

laboratory used in another part of the Fluoropolymers study, the synthetic air used in 

testing at UDRI was not analyzed for fluoride.

(3) For a given duration, polymer thermal degradation increases with increasing 

temperature. Hence, if thermal degradation of the perfluoroelastomer O-ring under 

thermal blank (and experimental run conditions) were the main contributor to thermal 

blank fluoride levels, thermal blank fluoride concentrations should positively correlate 

with O-ring (T4 nut) temperatures. However, comparison of T4 nut temperatures to 

fluoride levels for the 28 thermal blanks samples collected in this study does not reveal a 

clear trend even if the thermal blank results from Run 8 onward were blank corrected for 

the fluoride ion concentration of the HPLC water. More recent information indicates that 

for conditions at thermal blank (and experimental run) temperatures HF off-gassing from 

two perfluoroelastomer O-rings (Kalrez® 8900 and Kalrez® 8475) is not expected to be 

significantly different from HF off-gassing from silicone (VMQ-T1) O-rings; see Figures 11, 

12, and 14 of the enclosed 2009 AVS Symposium technical paper “Outgassing 

Characterization of Elastomeric Seals Used in Semiconductor Wafer Processing.”

Based on the information provided in points (1), (2), and (3) above, there is not sufficient 

information available to correct the experimental run impinger fluoride ion results for 

background fluoride levels. If the experimental run fluoride ion results for Runs 8-12 were 

corrected for the 0.037 mg/L level in the HPLC water used in these runs, the fluoride 

recoveries from these five runs would decrease from the range of 100% to 120% in Table 

18 of the Fluoropolymers Final Study Report to the range of 97% to 116%. However, blank 

correction here would not be consistent with the approach used in the data validation of 

the fluoride ion analytical laboratory data package in Appendix 1 to the Fluoropolymers 

Final Study Report, for the experimental run fluoride ion results are 13 to 22 times higher 

than the associated thermal blank values.
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The variability in the fluoride ion recoveries cannot be thoroughly explained by the factors 

discussed above. But the range of fluoride ion recoveries for this experimental program 

(Table 18) is generally consistent with the range of single-operator mean recoveries for 

repeat fluoride determinations by ion chromatography across the aqueous matrices 

evaluated (73% to 101%) for Method 300.0 (Table 2A in EPA, 1993) and with the range of 

fluoride recoveries using the IonPac AS4A-SC Column (57.0% to 109.0%) across types of 

water samples (Table 4 in Dionex, 2004). 

Literature Cited:

EPA, 1993. Method 300.0: Determination of Inorganic Anions by Ion Chromatography, 

Revision 2.1, August 1993.

Dionex, 2004. Application Note 133: Determination of Inorganic Anions in Drinking Water 

by Ion Chromatography.

2. Area #4 – CGA Concerns

Issues were encountered during testing that involved the continuous gas analyzer (CGA). During the post-run 

thermal blank for the third run, the CGA unexpectedly shutdown and the post-run thermal blank had to be rerun. 

As a result of this issue, the CGA was serviced by the manufacturer prior to the seventh set of runs. It is noted in 

the final report on page 47 that the pressure drop across the CGA decreased to 14 inches W.C. during the final six 

runs compared to 22 inches W.C. that was observed during the first six runs. It was also noted that the records for

the recalibration of the CGA after it was serviced were not provided (see Area #8). It is not clear how this pressure 

drop may have affected the final results or if it had any effect at all.

Additionally, during part of the ninth post-run steam cleaning and all of the twelfth post-run steam cleaning, the 

CGA was connected to the reactor system exhaust gas. The established protocol was to not have the CGA 

connected during steam cleanings to prevent condensation from occurring in the tubing of the machine. It is not 

clear how this affected the final results or if it had any effect at all.

EPA raises questions about (a) recalibration of the continuous gas analyzer (CGA) following 

service by the manufacturer prior to beginning Run 7 (see page 47 of Final Study Report)

and documentation of this recalibration, (b) the potential impact of the change in pressure 

drop across the CGA as a result of such service, and (c) potential effect of the CGA being 

connected to the reactor system exhaust during post-run steam cleaning for part of Run 9 

and all of Run 12. 

Items (a) and (c) were addressed in the July 12, 2013 electronic mail message to Joe Avcin 

(EPA) from Philip Taylor (UDRI). The potential impact of the change in pressure drop 

across the CGA as a result of CGA service is addressed here.

The October 7, 2009 Corrective Action Form by Richard Striebich (included in Appendix 1 

to the Final Study Report) concerning the CGA flow sensor bypass provides a starting point. 

This Corrective Action Form explains that the CGA read low for CO2 following the flow 

sensor bypass, referring to the low readings for CO2 during Runs 7, 8, and 9 as the result of 

drift. Review of the CO2 readings in Table 14 of the Final Study Report and in the relevant 
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run checklists before and after the CGA flow sensor bypass in Appendices 49 and 58 of the 

Final Study Report as well as pages 61-65, 67-68, 72, 78-82 Richard Striebich’s Phase II 

notebook in Appendix 36 of the Final Study Report indicates that the change in back 

pressure (pressure drop across the CGA) apparently contributed to this drift. As the 

stoichiometric calculations in Appendix 10 to the Final Study Report show, reactor 

pressure = room pressure + back pressure. Using 740 torr as a typical value for room 

pressure, the ratio of reactor pressure with 14 inches W.C. back pressure to reactor 

pressure with 22 inches W.C. is 0.98. This ratio is within the span gas-based correction 

factor used for CO2 in Table 14 of the Final Study Report, indicating that the change in back 

pressure helps account for the CO2 drift during runs 7, 8, and 9.

As the October 7, 2009 Corrective Action Form notes, the full CGA recalibration for CO2

prior to beginning run 10 brought the CGA readings for CO2 back to the same levels 

observed before CGA service and the correction factor using known and measured CO2

concentration of span gas corrected the run average CO2 values in Table 14 of the Final 

Study Report. Hence, the impact of the change in pressure drop across the CGA has been 

accounted for in the Final Study Report.

3. Area #6 – Other Perfluorinated Compounds

The identity of the ions associated with some peaks in the chromatograms at various points during the experiment 

were not clear. What is the likelihood that there were other perfluorinated compounds present in the samples?

EPA asks whether unmarked apparent peaks in the LC/MS/MS chromatograms for 

experimental runs represent other perfluoroinated compounds in the samples. 

Examination of the chromatograms by an LC/MS/MS expert indicates that the unmarked 

apparent peaks on these chromatograms were instrument noise. Furthermore, review of 

the LC/MS/MS analytical method (Exygen Method No.: 1M-008-046 Revision 1 as modified 

by the ECA) specified in the QAPP and included in the Final Study Report (included in 

Appendix 69 to the Fluoropolymers Final Study Report) shows that the only transition 

monitored was 413  369, confirming that the only analyte determinable by the 

LC/MS/MS method in use was the PFO anion.