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FEASIBILITY OF A NEW DIFFUSIVE SAMPLER TO MEASURE SUB-PPB LEVELS OF VOCs Linda Coyne Cindy Kuhlman SKC Inc. Eighty Four, PA.

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Presentation on theme: "FEASIBILITY OF A NEW DIFFUSIVE SAMPLER TO MEASURE SUB-PPB LEVELS OF VOCs Linda Coyne Cindy Kuhlman SKC Inc. Eighty Four, PA."— Presentation transcript:

1 FEASIBILITY OF A NEW DIFFUSIVE SAMPLER TO MEASURE SUB-PPB LEVELS OF VOCs Linda Coyne Cindy Kuhlman SKC Inc. Eighty Four, PA

2 Background Canisters are routinely used to sample VOCs at sub-ppb levels. Canisters are routinely used to sample VOCs at sub-ppb levels. Canisters provide accurate, sensitive, and reproducible measurements. Canisters provide accurate, sensitive, and reproducible measurements. However, they have a number of logistical disadvantages including size, expense, and training required for use. However, they have a number of logistical disadvantages including size, expense, and training required for use.

3 Diffusive Samplers: A Possible Alternative to Canisters ADVANTAGES Inexpensive and simple to operate Inexpensive and simple to operate Lightweight and unobtrusive Lightweight and unobtrusiveDISADVANTAGES Sensitivity issues Sensitivity issues Reverse diffusion effects Reverse diffusion effects Demonstrate starvation at face velocities less than 5 cm/sec Demonstrate starvation at face velocities less than 5 cm/sec

4 Diffusive Samplers: Widely studied for ppm levels Many studies have been published on the use of badge style diffusive samplers for industrial hygiene applications using solvent extraction and analysis by GC/FID/MS Many studies have been published on the use of badge style diffusive samplers for industrial hygiene applications using solvent extraction and analysis by GC/FID/MS Data indicates badges produce consistent and accurate measurements for many compounds. Data indicates badges produce consistent and accurate measurements for many compounds. Validation studies have documented reliable results under various conditions of use. Validation studies have documented reliable results under various conditions of use.

5 Diffusive Samplers: New studies for sub-ppm levels New Studies New Studies –Marines: Nerve agents –OSHA: VOCs for Indoor Air –Sweden: 1,3-butadiene and benzene

6 Diffusive Samplers: Indoor and Ambient Air Studies In order to consistently measure sub-ppb and ppt levels of VOCs with a diffusive sampler, thermal desorption must be used. In order to consistently measure sub-ppb and ppt levels of VOCs with a diffusive sampler, thermal desorption must be used.

7 Ultra Badge A modification of the SKC 575-series solvent- desorption badge for VOCs was made which added an aluminum funnel to back of badge. A modification of the SKC 575-series solvent- desorption badge for VOCs was made which added an aluminum funnel to back of badge. The funnel allowed for transfer of sorbent from badge to tube. The funnel allowed for transfer of sorbent from badge to tube. The tube could then be analyzed by thermal desorption. The tube could then be analyzed by thermal desorption.

8 Sorbent Storage and Transfer from Badge Initial Problems Discovered Initial Problems Discovered –Sorbent could not be stored for any length of time in badge housing due to contamination. –The use of SS tubes did not allow users to see the sorbent transfer. –Field tests indicated that users did not like to handle tube separators that were used to seal the tube after transfers.

9 NEXT DEVELOPMENT: ULTRA II SAMPLER

10 ULTRA II DESIGN MODIFICATIONS Built-in funnel was redesigned such that a 4-mL screw cap vial could be attached to back of badge. Built-in funnel was redesigned such that a 4-mL screw cap vial could be attached to back of badge. User can easily see the transfer of sorbent. User can easily see the transfer of sorbent.

11 Front and Back of Sampler

12 Filling the Sampler

13 Emptying the Sampler

14 Ultra II Diffusive Sampler BEFORE SAMPLING Sorbent contained in a vial can be transferred to the badge immediately before sampling, which addresses contamination concerns. Sorbent contained in a vial can be transferred to the badge immediately before sampling, which addresses contamination concerns. AFTER SAMPLING The sorbent can be transferred back to vial and capped for shipment to the lab. The sorbent can be transferred back to vial and capped for shipment to the lab. In the laboratory, the sorbent can be transferred to a TD tube for analysis. In the laboratory, the sorbent can be transferred to a TD tube for analysis.

15

16 Sampling Accessories: Vial Containing the Sorbent

17 Sampling Accessories: Sampling Stand

18 Evaluation of the Ultra II Sampler Duplicate precision Duplicate precision Audit accuracies Audit accuracies Method reporting limits Method reporting limits Storage studies of both tubes and vials Storage studies of both tubes and vials Sampling rates of badge for target compounds Sampling rates of badge for target compounds

19 VOCs Evaluated VAPOR INTRUSION VAPOR INTRUSIONAPPLICATIONS Trichloroethylene and perchloroethylene were evaluated as typical compounds. OTHER APPLICATIONS OTHER APPLICATIONS Benzene, toluene, xylenes, heptane, and 1,2-DCE were also evaluated.

20 Sample Media Selection REFERENCE METHOD EPA Compendium Method TO-17 was used as a reference to select the best sorbent media for these compounds EPA Compendium Method TO-17 was used as a reference to select the best sorbent media for these compounds SORBENTS USED Tenax TA Tenax TA (20/35 mesh) Anasorb GCB1 (60/80 mesh) Anasorb GCB1 (60/80 mesh) –Equivalent to Carbopack B

21 Analytical Conditions Samples were desorbed using a Perkin Elmer Turbomatrix ATD. Samples were desorbed using a Perkin Elmer Turbomatrix ATD. Focusing trap was a dual bed of Tenax TA and Carbopack B. Focusing trap was a dual bed of Tenax TA and Carbopack B. Separation was performed using a Perkin Elmer Clarus 500 FID/GC. Separation was performed using a Perkin Elmer Clarus 500 FID/GC.

22 Performance Criteria Method reporting limits Method reporting limits Audit accuracies Audit accuracies Precision Precision

23 Sampling Rates and MRL for VOCs Compound SR MRL 8-h 24-h (mL/min) (ng) (ppt) (ppt) Ethylbenzene Ethylbenzene Benzene Benzene p-Xylene p-Xylene o-Xylene o-Xylene Dichloroethane Dichloroethane

24 Sampling Rates and MRL for VOCs Compound SR MRL 8-h 24-h (mL/min) (ng) (ppt) (ppt) Heptane Toluene Chlorobenzene Trichloroethylene Perchloroethylene

25 Storage of TCE and PCE on Tenax TA in Tubes, - 3 C (%Recovery ±RSD) Storage Time (weeks ) Trichloroethylene (10 ng) Perchloroethylene (10 ng) 1 week 1 week 106 ± ± ± ±11 2 weeks 112 ± ± ± ±9.3 3 weeks 121 ± ± ± ±8.3

26 Storage of TCE and PCE on Anasorb GCB1 in Tubes, - 3 C (%Recovery ±RSD) Storage time TrichloroethylenePerchloroethylene 1 week 96.2 ± ± ±4.7

27 Storage of TCE and PCE Tenax TA in Vials, - 3 C (%Recovery ±RSD) Storage time (weeks) Trichloroethylene (10 ng) (10 ng)Perchloroethylene 1 week 122 ± ±6.1 2 weeks 150 ± ±25 3 weeks 89.5 ± ±3.1

28 Storage of TCE and PCE on Anasorb GCB1 in Vials, - 3 C (%Recovery ±RSD) Storage time TrichloroethylenePerchloroethylene 1 week 122 ± ±18 2 weeks 115 ± ±2.1 3 weeks 94.8 ± ±8.0

29 Audit Accuracies on Tenax TA Trichloroethylene Compound Level (ng) Accuracy (%) Trichloroethylene Mean Mean104.2

30 Audit Accuracies on Tenax TA Perchloroethylene Compound Level (ng) Accuracy (%) Perchloroethylene Mean Mean

31 Audit Accuracies on Anasorb GCB1 Trichloroethylene Compound Level (ng) Accuracy (%) Trichloroethylene Mean Mean

32 Audit Accuracies on Anasorb GCB1 Perchloroethylene Compound Compound Level (ng) Level (ng) Accuracy (%) Accuracy (%) Perchloroethylene Mean Mean

33 Audit Accuracies on Chromosorb 106 Trichloroethylene Compound Level (ng) Accuracy (%) Trichloroethylene Mean Mean106.3

34 Audit Accuracies with Tenax TA Other VOCs Compound Range tested (ng) Mean Accuracy (%) Benzene 0.8 – (n=32) 1,2- Dichloroethane (n=19) Toluene 0.86 – (n=29)

35 Audit Accuracies with Anasorb GCB1 Other VOCs Compound Range tested (ng) Mean Accuracy (%) Benzene 1.0 – (n=18) Ethyl Benzene (n=21) P-Xylene (n=20)

36 Duplicate Precision Data Chlorinated Compounds Sampled on the Ultra II TCE PCE 1,2-DCE TCE PCE 1,2-DCE ng ppt ng ppt ng ppt ng ppt ng ppt ng ppt Badge A Badge B Precision 2.8 % 9.5 % 13.4 % Criteria of acceptance: ±20 %

37 Field Studies Field study underway in the State of New York Field study underway in the State of New York Comparison of diffusive badges and canisters in indoor air Comparison of diffusive badges and canisters in indoor air Study completed in May 2005; data to be tabulated in June, 2005 Study completed in May 2005; data to be tabulated in June, 2005

38 Conclusions - Diffusive samplers provide logistical advantages. Diffusive Samplers Diffusive Samplers –Small, unobtrusive –Low shipping costs –Easy to use –Initial purchase of badge <$100 –Disposable –No recertification costs Canisters Canisters –Bulky –High shipping costs –Training necessary for use –Higher costs for purchase or rental –Recertification costs

39 Conclusions - Diffusive sampler design can be optimized for sub-ppb analysis. –A choice of sorbents to optimize collection efficiency. –Sorbent cleaning, storage and handling options that avoid contamination –Thermal desorption analysis to permit sensitivities in the range of ppt

40 Conclusions The Ultra II diffusive sampler is an example of a badge that has been optimized for low level sampling/analysis of VOCs. The Ultra II diffusive sampler is an example of a badge that has been optimized for low level sampling/analysis of VOCs. The badges are easy to use, lightweight and offer a number of logistical advantages to users. The badges are easy to use, lightweight and offer a number of logistical advantages to users. Initial data show that the badges are accurate and precise and provide detection limits needed in the field. Initial data show that the badges are accurate and precise and provide detection limits needed in the field.


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