Analysis of Waste Solvent by Purge & Trap

Importance of the topic

Purge and trap analysis is a cornerstone technique for trace-level determination of volatile organic compounds in complex matrices. It enables efficient removal of volatiles via inert gas sparging and concentration on sorbent traps, which is critical for monitoring halogenated organics in waste solvents and ensuring environmental compliance before disposal.

Objectives and overview

This study compares static headspace and purge & trap with cryogenic focusing for quantifying halogenated contaminants in an alcohol-based waste solvent used for parts cleaning. The goal is to assess method sensitivity and selectivity for reliable detection of trace halogenated materials.

Methodology and used instrumentation

• Static headspace: 10 mL sample heated at 70 °C for 30 min; 4 mL headspace injected into GC.
• Purge & trap: 5 mL sample diluted with water; helium purge at 30 mL/min for 10 min; Trap A (Tenax) desorbed at 250 °C for 10 min; cryogenic focusing (Trap B) at –100 °C, desorbed at 200 °C for 5 min; valve oven and transfer line at 250 °C.
• Gas chromatography: Varian 3700 GC with flame ionization detector; SE-54 capillary column (50 m × 0.25 mm i.d.); oven program: 50 °C for 2 min, then 6 °C/min to 200 °C.
• Sample concentration: COS 330 Sample Concentrator.

Main results and discussion

Purge & trap with cryogenic focusing delivered superior sensitivity and resolved low-level halogenated peaks that were masked by the high-abundance alcohol in static headspace analysis. Chromatograms exhibited sharp, well-defined peaks for targeted organohalogen compounds, enabling precise quantification.

Benefits and practical applications

• Enhanced detection limits and peak resolution for volatile organics.
• Effective suppression of high-concentration matrix interferences.
• Versatile applicability to environmental water, soils, foods, polymers, pharmaceuticals, and fire debris.
• Supports regulatory compliance, waste minimization, and solvent recovery programs.

Future trends and possibilities

Anticipated developments include fully automated purge & trap systems, integration with FTIR and mass spectrometry for compound identification, novel sorbent materials for broader volatility range, and field-deployable interfaces. Hyphenation with gel permeation chromatography-infrared (GPC-IR) promises combined profiling of complex polymer formulations and additives.

Conclusion

Purge & trap with cryogenic focusing outperforms static headspace for analysis of halogenated organics in waste solvents, offering high sensitivity, robust separation, and accurate quantitation. When combined with GC-FID and GPC-IR, this approach significantly expands analytical capabilities for environmental monitoring and materials characterization.

References

• T. Bellar and J. Lichtenberg, Identification of an aliphatic polyester resin, J. Am. Water Works Assn., 66(12):739.
• T. Wampler, W. Bowe, J. Higgins, E. Levy, Systems approach to automatic cryofocusing in purge and trap, Am. Lab., 17(8):82 (1985).
• J. Grote, Apparatus for concentration of volatile organic pollutants in water, Am. Lab., 7(2):47 (1975).