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

Transcription

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 215 Evaluated a proprietary cleaning procedure for stubborn canisters 217 Fill gas impacts Un-Coated vs. Silicon-Lined 216 Evaluated storage time, sweep gas, and temperature impacts on blank concentrations

4 Why all the focus on canister blanks/cleaning? Compound 1-in-1-million Noncancer effects cancer risk (pptv) (pptv) Acrolein NA 9 Naphthalene Propylene Dichloride ,3-Butadiene 15 9 Acrylonitrile Ethylene Dibromide Methyl Bromide NA 13 Benzene Carbon Tetrachloride Vinyl Chloride ,4-Dichlorobenzene Ethylbenzene ,1,2,2- Tetrachloroethane 2.5 NA Ethylene Dichloride 9.5 NA Tetrachloroethylene 25 NA Trichloroethylene 93 NA 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 26 kpa (3 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.2 ppbv of targeted VOCs) should not be used.

6 Guidance for Canister Cleaning Evacuate down to 5 mtorr Hold under vacuum for 6 minutes Fill with humidified zero air to 3 psig Repeat cycle two additional times for a total of three cycles

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

8 Storage Time Recap from Day pptv Sum Day pptv 2-Butanone (MEK) Day pptv Acrolein Day pptv Acetone Day pptv Propylene Day pptv Isopropyl Alcohol

9 pptv Sweep Gas Recap from Butanone Isopropyl Acrolein SumAlcohol (MEK) Day Sweep Gas Air 14 Nitrogen 14

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 3 psig with 5% RH air 1 ml sample volumes SIM calibrated from 1 to 3 pptv

11 Ethylene to Hexachlorobutadiene Ethylene to Hexachlorobutadiene Rxi-1 15 m x.25 mm x 1. µm -45 ⁰C for 4. min then 4.5 C/min to 125 C for min then 9. C/min to 25 C for min

12 36 Cleaning Cycles Results Un-Filtered House Air 12 Cycles 36 Cycles Average Average n = 12 n = 12 Propylene Dichlorodifluoromethane (Freon 12) n-butane n-pentane Trichlorofluoromethane (Freon 11) Ethanol Carbon disulfide Acrolein 41 3 Isopropyl alcohol Methylene chloride Acetone Hexane Tetrahydrofuran Butanone (MEK) Heptane Benzene Toluene Hexanone (MBK) Naphthalene 7 12

13 Newly Renovated Innovations Lab

14 The Fix

15 Fill Gas Fix House Air 12 Cycles S-Trap Average Average n = 12 n = 12 Propylene 246 ND Dichlorodifluoromethane (Freon 12) 156 ND n-butane 281 ND n-pentane 167 ND Trichlorofluoromethane (Freon 11) 26 ND Ethanol Carbon disulfide Acrolein 41 ND Isopropyl alcohol Methylene chloride Acetone Hexane 536 ND Tetrahydrofuran Butanone (MEK) Heptane 41 ND Benzene Toluene Hexanone (MBK) 26 ND Naphthalene 7 ND

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 Cleaned2 Average He Average He Average Air Average Air n = 6 n = 6 n = 6 n = 6 Propylene Dichlorodifluoromethane (Freon 12) ND ND n-butane n-pentane ND ND Trichlorofluoromethane (Freon 11) ND ND Ethanol Carbon disulfide Acrolein Isopropyl alcohol Methylene chloride Acetone Hexane ND ND Tetrahydrofuran Butanone (MEK) Heptane ND 27 ND ND Benzene Toluene Hexanone (MBK) Naphthalene

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 Average n=24 n=24 Propylene Dichlorodifluoromethane (Freon 12) n-butane Trichlorofluoromethane (Freon 11) Ethanol 17 ND Acrolein ND ND Isopropyl alcohol Methylene chloride Acetone Tetrahydrofuran Butanone (MEK) Heptane 5 61 Benzene Toluene Hexanone (MBK) Naphthalene

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