Analysis of Stack Emissions Using VOST Air Sampling Tubes and Capillary GC

Significance of the Topic

Accurate measurement of volatile organic compounds in stack emissions is critical for ensuring compliance with environmental regulations and minimizing human health risks. The US EPA SW-846 Method 0030 defines a standardized sampling protocol, yet practical application requires reliable adsorbent materials that deliver low background interference and high recoveries across a broad boiling point range.

Study Objectives and Overview

This application study evaluates the performance of Supelco VOST air sampling tubes for VOC sampling under Method 0030 and subsequent analysis by GC/MS. Key aims include demonstrating low blank levels, robust sample integrity during transport, and compatibility with downstream thermal desorption and purge-and-trap procedures per Method 5041.

Methodology and Used Instrumentation

Sampling was performed with a two-tube VOST train: VOST 100 packed with Tenax TA 35/60 and VOST 200 packed with a Tenax TA/petroleum charcoal (2:1 v/v) blend. Air volumes of 5–20 L were collected at flow rates of 250–1 000 mL/min. Following sampling, tubes underwent thermal desorption into organic-free water via a purge-and-trap concentrator. Analysis was performed on a capillary GC with a 75 m × 0.53 mm SPB-624 column and FID detector (oven program 35 °C to 200 °C at 10 °C/min). Key instrumentation components:

• VOST 100 and VOST 200 sampling tubes
• PUF cartridge assembly
• VOCARB-4000 purge trap
• SPB-624 fused-silica capillary column
• GC/FID system

Main Results and Discussion

Background levels for individual VOCs were consistently below 20 ng per compound. Surrogate recoveries (chloro-benzene-d₅) ranged from 50 % to 150 %, and pressure drop across tubes remained under 5 inches of water at 50 mL/min. Chromatographic comparison of a 20 ng calibration standard with spiked blank tubes confirmed negligible adsorbent interferences and complete elution of target analytes. These findings validate the high-purity adsorbents and the efficacy of the dual-tube configuration in capturing volatile and semivolatile species while minimizing water carryover.

Benefits and Practical Applications

• Compliance with EPA SW-846 Methods 0030 and 5041
• Low background for trace-level analysis
• Wide compound coverage (boiling points 30–100 °C and beyond)
• Reusable tubes after thermal conditioning
• Customizable tube dimensions and adsorbent configurations

Future Trends and Potential Applications

Advances may include development of mixed-mode sorbents with enhanced polar compound recovery, integration of online thermal desorption modules for real-time monitoring, and coupling with high-resolution mass spectrometry for comprehensive speciation of emerging contaminants.

Conclusion

Supelco VOST sampling tubes offer a validated, low-background solution for VOC emission monitoring in hazardous waste incinerator stacks. The dual-adsorbent configuration and compatibility with EPA-approved analytical workflows ensure reliable quantitative data essential for regulatory enforcement and environmental health assessments.

References

• US EPA SW-846 Method 0030: Volatile Organic Sampling Train
• US EPA SW-846 Method 5041: Protocol for Analysis of Sorbent Cartridges from VOST