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Reporter U.S. Vol. 30.1

Sampling VOCs with Supel™-Inert Film Gas Sampling Bags

Sampling VOCs with Supel™-Inert Film Gas Sampling Bags with Thermogreen™ LB-2 Septa as an Alternative to Tedlar®

Kristen Schultz and Jamie Brown
Introduction
For 10 years, Supelco has provided our customers with high quality Tedlar gas sampling bags. Recently, we expanded our gas sampling bag line to include an alternative to Tedlar for sampling VOCs that incorporates our low-bleed Thermogreen™ LB-2 septa in the valve fitting.

Key Features and Benefits
  • Inertness properties similar to Tedlar for a wide range of compounds
  • Suitable for sampling and analysis for most VOC’s within 2 days and many sulfur compounds for up to 24 hrs
  • Chemically inert to most acids, aliphatic and aromatic organic compounds, chlorinated solvents and alcohols
  • Abrasion resistant
  • No static properties; unlike other alternative films, the Supel-Inert Film does not cling to bench-tops and other materials
  • Two fittings available: Push-Pull Lock Valve (PLV) and Screw Cap Valve (SCV)

Bag Composition & Construction
Supel-Inert Film is composed of a fluoropolymer film, (PVDF; polyvinylidene difluoride) specifically engineered for sampling VOCs from air, manufactured to the highest standards from ultra clean, high-quality materials. They are leak tested at both the hermetically sealed seams and at the valve fittings to ensure tight and strong seals and minimize sample loss. The Supel-Inert film materials are proprietary materials to Supelco.

Testing the VOC Background
New sampling bags (right out of the box) were filled with 1-Liter of clean dry nitrogen. The bags were allowed to sit for 1-hour at room temperature. Then the entire contents of the bag was concentrated onto a Carbotrap™ 300 thermal desorption tube (21705-U) by empting the bag using an air sampling pump at a flow rate of 100 mL/min. Each tube was thermal desorbed by a PerkinElmer Thermal desorber at 330 °C for 5 minutes.

Results – VOC Background
Figure 1 demonstrates that Supel-Inert film bags have a lower VOC background, <10 ppb of the TO-15 calibration mix (after incubation of 1-hour) right out of the box compared to Tedlar and Competitor K. The bottom chromatogram shows the EPA TO- 15 calibration mix (41973-U) spiked at a concentration of 10 ppb; in the middle is Competitor K, above is Supel-Inert Film and the top is Tedlar film. The Tedlar shows peaks of DMAC and phenol.

Table 1. Comparison of Supel-Inert Film and Tedlar Film
  Supel-Inert Film Tedlar Film
Thickness 3 mil 2 mil
Tensile Strength 6100 psi (42 MPa) 8000 psi (55 MPa)
Max Operating Temp 150 °C (302 °F) 204 °C (400 °F)
Specific Gravity 1.78 g/mL 1.70 g/mL
Oxygen Permeability 58 mL/(m² x d) 50 mL/(m² x d)
Water Vapor Permeability 12-15 g/(m² x d) 9-57 g/(m² x d)
Carbon Dioxide Permeability 172 mL/(m² x d) 172 mL/(m² x d)

Figure 1. Comparison of the VOC Background for Supel-Inert, Tedlar and Competitor K Bags (Calibration Standard 10 ppb)



Testing the VOC Recovery
New sampling bags were purged 2 times with clean dry nitrogen. The bags were then filled with 1-liter of TO-15/17 Calibration Gas Mix (62-components) at 1 ppm each (41973-U). After the specified time (4, 24, 48 and 120 hr) a 12.5 mL sample was taken from each bag using a GasTight® syringe. The contents of the syringe was spiked (concentrated) onto a Carbotrap 300 thermal desorption tube (21705-U) by injecting the syringe contents into the Adsorbent Tube Injector System (ATIS) 28520-U with a Carbotrap 300 attached to the outlet. Each tube was thermally desorbed using a PerkinElmer TurboMatrix™ -150 thermal desorber at 330 °C for 5 minutes. A four-point calibration curve was performed by spiking the same gas mix directly (3.2, 6.4, 9.4, and 12.5 mL ) from the gas cylinder onto the Carbotrap 300 tubes.

Table 2. VOC Recovery 4 hrs to 120 hrs – 62 Component Mix
Compound % Recovery
4-hr 24-hr 48-hr 120-hr
Propylene 88 111 114 89
Propylene 88 111 114 89
Halocarbon 12 98 98 106 93
Chloromethane 96 96 91 70
Halocarbon 114 104 100 105 97
Vinyl chloride 92 95 96 77
1,3-Butadiene 107 104 112 92
Bromomethane 105 123 97 77
Chloroethane 92 95 98 79
Ethanol 145 125 88 64
Acetone 79 60 51 29
Halocarbon 11 103 99 106 91
1,1-Dichloroethene 98 96 99 80
Methylene chloride 94 88 85 59
Halocarbon 113 102 98 104 89
Carbon Disulfide 100 95 91 66
trans-1,2-Dichloroethene 97 91 89 62
1,1-Dichloroethane 104 95 97 78
Methyl Tertiary Butyl Ether 99 96 99 84
2-Butanone 79 57 42 25
cis-1,2-Dichloroethene 95 85 81 54
Ethyl Acetate 86 66 53 13
Hexane 110 95 99 78
Chloroform 102 93 94 70
Tetrahydrofuran 94 77 68 46
1,2-Dichloroethane 94 79 71 45
1,1,1-Trichloroethane 101 95 97 77
Benzene 94 84 79 52
Carbon tetrachloride 101 95 97 76
Cyclohexane 102 97 99 80
 
Compound % Recovery
4-hr 24-hr 48-hr 120-hr
1,2-Dichloropropane 98 84 79 54
Bromodichloromethane 101 85 80 52
Trichloroethene 89 85 77 50
Heptane 105 95 95 69
Methyl Isobutyl Ketone 80 53 40 23
cis-1,3-Dichloropropene 95 66 53 30
trans-1,3-Dichloropropene 90 52 38 19
1,1,2-Trichloroethane 93 72 61 35
Toluene 89 68 56 31
2-Hexanone 61 29 20 13
Dibromochloromethane 97 77 68 39
1,2-Dibromoethane 89 60 44 24
Tetrachloroethene 99 81 73 42
Chlorobenzene 77 53 39 20
Ethylbenzene 84 59 45 24
m & p-Xylene 73 49 34 19
Bromoform 97 61 48 26
Styrene 59 33 23 13
1,1,2,2-Tetrachloroethane 87 56 42 22
o-Xylene 69 45 31 17
4-Ethyltoluene 64 40 27 15
1,3,5-Trimethylbenzene 55 34 22 13
1,2,4-Trimethylbenzene 47 27 19 12
Benzyl Chloride 27 16 11 7
1,3-Dichlorobenzene 50 27 18 11
1,4-Dichlorobenzene 47 25 17 11
1,2-Dichlorobenzene 41 21 15 10
1,2,4-Trichlorobenzene 26 19 11 13
Hexachlorobutadiene 58 35 22 14

*Note: Order based on typical GC retention

Results – VOC Recovery
After 2 days of ambient storage, 25 representative compounds showed recoveries of >80%; even after 5 days, 9 of these compounds still showed recovery of >80%. The same compounds tested in Tedlar exhibited similar results.

Conclusions
Based on the results from the background and recovery data, Supel-Inert gas sampling bags provide a low background compared to Tedlar and Competitor K, and are suitable for sampling most VOCs comparably to Tedlar.

Featured Products
Description Push Lock
Valve (PLV)
Screw Cap
Valve (SCV)
Supel-Inert Gas Sampling Bags with Thermogreen LB-2 Septa
1 L, 7 x 9 in. (17.8 x 22.9 cm), 10 Pk 30213-U 30221-U
2 L, 9 x 11 in. (22.9 x 27.9 cm), 10 Pk 30214-U 30222-U
5 L, 12 x 14 in. (30.5 x 35.6 cm), 10 Pk 30215-U 30223-U
10 L, 12 x 21 in. (30.5 x 53.3 cm), 10 Pk 30216-U 30224-U
25 L, 19 x 25 in. (48.3 x 63.5 cm), 5 Pk 30217-U 30225-U

Description Cat. No.
Thermal Desorption Tubes
Carbotrap 300 Stainless Steel TD Tube, preconditioned, 10 ea. 21705-U
Standards
EPA TO-15/TO-17 Gas Calibration Mix (62 component), 1 ppm each in N2, 110 L 41973-U
Instruments
ATIS (Adsorbent Tube Injection System), 110 V 28520-U
ATIS (Adsorbent Tube Injection System), 230 V 28521-U
Analytical Column
SPB-HAP, 60 m x 0.32 mm x 4 µm 25020-U

TRADEMARKS: Carbotrap, Thermogreen, Supel – Sigma-Aldrich Co. LLC; GasTight – Hamilton Co.; TurboMatrix – PerkinElmer Corp.; Tedlar - E.I. du Pont de Nemours & Co., Inc.