1. Silicon-Lined Canister Cleaning Practices and Blank VOC Concentrations
Jason S. Herrington, Gary Stidsen, Trent Sprenkle, Steve Kozel

2. U.S. EPA Method TO-15
A “guidance document” for a Performance Based Method (PBM)
Means a laboratory can meet performance criteria by hook or crook

3. NEMC Canister Blank/Cleaning “Trilogy”
2015
Evaluated a proprietary cleaning procedure for stubborn canisters
2016
Evaluated storage time, sweep gas, and temperature impacts on blank concentrations
2017
Fill gas impacts
Un-Coated vs. Silicon-Lined

4. Why all the focus on canister blanks/cleaning?
Compound
1-in-1-million cancer risk (pptv)
Noncancer effects (pptv)
Acrolein NA 9
Naphthalene
5.6
570
Propylene Dichloride 11
870
1,3-Butadiene 15
900
Acrylonitrile
6.8
920
Ethylene Dibromide
0.22
1200
Methyl Bromide
1300
Benzene 39
9200
Carbon Tetrachloride 26
16000
Vinyl Chloride 44
38000
1,4-Dichlorobenzene
133000
Ethylbenzene 92
230000
1,1,2,2-Tetrachloroethane
2.5
Ethylene Dichloride
9.5
Tetrachloroethylene 25
Trichloroethylene 93
GC-MS systems are getting more sensitive
Preconcentrators are advancing
Canister cleaning remains unchanged…

5. TO-15 Blank Criteria
At the end of the evacuation/pressurization cycle, the canister is pressurized to 206 kPa (30 psig) with humid zero air. The canister is then analyzed by a GC/MS analytical system. Any canister that has not tested clean (compared to direct analysis of humidified zero air of less than 0.2 ppbv of targeted VOCs) should not be used.

6. “Guidance” for Canister Cleaning
8.4.1 Evacuate down to 500 mTorr
Hold under vacuum for 60 minutes
Fill with humidified “zero air” to 30 psig
Repeat cycle two additional times for a total of three cycles

7. Blank Contributions Canister Cleaning Oven Fill Gas Storage Time
Uncoated
Coated
Cleaning Oven
Cycle Time
Temperature
Cycles
Sweep Gas
DI Water for Humidification
Fill Gas
Storage Time
Connection Lines
Preconcentrator
GC-MS

8. Storage Time Recap from 2016

9. Sweep Gas Recap from 2016

10. Cleaning Cycles Last year I used 12 cleaning cycles, so why not 36?
12 canisters
Cleaned 12 times and analyzed
Cleaned 24 more times and analyzed
All canisters filled to 30 psig with 50% RH air
1000 mL sample volumes
SIM calibrated from 10 to 300 pptv

11. Ethylene to Hexachlorobutadiene
Rxi m x 0.25 mm x 1.0 µm
-45 ⁰C for 4.0 min
then 4.5 °C/min to 125 °C for 0 min
then 9.0 °C/min to 250 °C for 0 min
Only 2 critical co-elutions. 2-Methylpentane and vinyl acetate; and n-hexane and ethyl acetate.
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
50.00

12. 36 Cleaning Cycles Results
Un-Filtered House Air
12 Cycles
36 Cycles
Average
n = 12
Propylene
246
199
Dichlorodifluoromethane (Freon® 12)
156
110
n-Butane
281
327
n-Pentane
167
Trichlorofluoromethane (Freon® 11) 26 22
Ethanol 11 49
Carbon disulfide
218
363
Acrolein 41 30
Isopropyl alcohol
111
Methylene chloride
1069
227
Acetone 14
Hexane
536
136
Tetrahydrofuran 36 39
2-Butanone (MEK)
297 38
Heptane 79
Benzene
150
245
Toluene
325 58
2-Hexanone (MBK)
Naphthalene 7 12

13. Newly Renovated Innovations Lab

14. The “Fix”

15. Fill Gas Fix House Air 12 Cycles S-Trap Average n = 12 Propylene 246ND
Dichlorodifluoromethane (Freon® 12)
156
n-Butane
281
n-Pentane
167
Trichlorofluoromethane (Freon® 11) 26
Ethanol 11 13
Carbon disulfide
218
177
Acrolein 41
Isopropyl alcohol 21
Methylene chloride
1069 16
Acetone
111 19
Hexane
536
Tetrahydrofuran 36 12
2-Butanone (MEK)
297 56
Heptane
Benzene
150 18
Toluene
325 9
2-Hexanone (MBK)
Naphthalene 7

16. 36 Cleaning Cycles Conclusions
“IDK” as I got derailed by the lab line contamination
Lesson learned: “Garbage in… garbage out”
Fill gas has more of bearing on blank concentrations than probably all the other variables put together
The zero in “zero air” is a relative term

17. Fill Gas Evaluation
Since the fill gas seemed almost more important than the cleaning itself
I took 6 new canisters and cleaned them and 6 new canister as is
Aged appropriately and analyzed

18. Fill Gas Evaluation Un-Filtered Fill Gas Uncleaned Cleaned Uncleaned2
Average He
Average Air
n = 6
Propylene
222
150 60 79
Dichlorodifluoromethane (Freon® 12) ND 87 89
n-Butane 38 17
244
202
n-Pentane
3121
3142
Trichlorofluoromethane (Freon® 11) 37 35
Ethanol 4 3 14 18
Carbon disulfide
163
140
496
Acrolein 50 28 86
Isopropyl alcohol 95 72
152
153
Methylene chloride 12
123
Acetone 70 57 78
Hexane
737
726
Tetrahydrofuran
147 93
208
137
2-Butanone (MEK)
203
174
165
158
Heptane 27
Benzene
179
Toluene 22 53 96
2-Hexanone (MBK)
111 75
1420
102
Naphthalene 15 5 25 30

19. Fill Gas Conclusion
The “zero-ness” of the zero air has more bearing on blank concentrations than anything else
This statement applies to clean canisters
The canister cleaning practices play a more significant role for dirty canisters
However, once a dirty canister becomes clean… zero air takes over again

20. Silicon-Lined Canisters
Customers always ask “what is the difference between coated and un-coated canisters?”
The response usually has focused on sample stability and not blank cleanliness
Obviously I wanted to generated the data so as to provide a reasonable response

21. Un-Coated vs Silicon-Lined
6 un-coated canisters and 6 silicon-lined canisters
Filled with He, Filtered He, Air, Filtered Air and analyzed
Trying to evaluate the actual difference in the canisters, not just the impact of the fill gas

22. Un-Coated vs Silicon-Lined
Blanks
Un-Coated
Silicon-Lined
Average
n=24
Propylene 62 46
Dichlorodifluoromethane (Freon® 12) 75 68
n-Butane
277
201
Trichlorofluoromethane (Freon® 11) 36 35
Ethanol
170 ND
Acrolein
Isopropyl alcohol
183
135
Methylene chloride
110
Acetone 52 22
Tetrahydrofuran
382
326
2-Butanone (MEK) 56 29
Heptane 50 61
Benzene
146
129
Toluene 63 26
2-Hexanone (MBK) 65 64
Naphthalene
156 16

23. Un-Coated vs Silicon-Lined Conclusions
Virtually indistinguishable, with a slight nod toward silicon-lined
This is intuitive, considering the surface differences
Would it even be statistically significantly different?
Ethanol and naphthalene clearly show differences

24. Thank You!
Co-authors
Markes International