Analysis of 1, 2, 3-Trichloropropane by Purge and Trap Concentration and Gas Chromatography/Mass Spectrometry (GC/MS)

Significance of the Topic

1,2,3-Trichloropropane (TCP) is a dense, persistent groundwater contaminant and a probable human carcinogen. Historically used as a solvent and intermediate in fumigant and polymer production, TCP resists biodegradation and tends to sink in aquifers, presenting long-term risks to drinking water supplies. Regulatory bodies such as the State of California have set maximum contaminant levels as low as 5 ppt, driving the need for highly sensitive analytical methods.

Aims and Study Overview

This work compares two modified EPA methods (524.2 and 8260C) for detecting TCP at ppt levels. The study evaluates the effects of increased purge temperature, sample volume, and desorption time on method sensitivity and robustness, aiming to identify a practical protocol for routine water monitoring.

Methodology and Instrumentation

• Sample Concentration: OI Analytical Eclipse 4760 Purge & Trap with 4100 autosampler
• Trap Composition: Tenax/silica gel/CMS (No. 10)
• Purge Conditions: 40 mL/min helium, heated to 50 °C, 11 min purge
• Desorption: 4 min at 180–210 °C for Method 524.2; 0.5 min for Method 8260C
• Gas Chromatography: Agilent 7890A, Rxi-624Sil MS column (30 m × 0.25 mm × 1.4 µm), split 20:1, temperature ramp 40 °C to 220 °C over 18 min
• Mass Spectrometry: Agilent 5975C in SIM mode, monitoring m/z 110 for TCP and relevant ions for internal and surrogate standards
• Calibration & QC: Seven-point range 5–500 ppt; daily bromofluorobenzene check; IDOC at 100 ppt; MDL study at 4 ppt

Main Results and Discussion

• Precision & Accuracy: All analytes showed <15% RSD; surrogates within acceptance criteria
• Detection Limits: Reporting limit of 5 ppt for TCP; MDL confirmed around 4 ppt
• Method Comparison: The 8260C variant (10 mL purge, 0.5 min desorb) matched the sensitivity of 524.2 while reducing water load on the system
• No TCP carryover observed up to 500 ppt; all field tap-water samples were non-detect

Benefits and Practical Applications

• Achieves regulatory compliance for trace TCP analysis in environmental water
• SIM detection enhances selectivity and sensitivity for low-level quantitation
• Short desorption cycles and optimized purge volumes improve throughput and instrument longevity

Future Trends and Potential Uses

• Development of portable purge-and-trap systems for on-site monitoring
• Advanced trap materials and higher purge temperatures for further sensitivity gains
• Integration with high-resolution MS to resolve co-eluting species and expand analyte scope
• Standardization of sub-ppt methods across regulatory frameworks

Conclusion

Optimized purge-and-trap GC/MS protocols, especially the streamlined USEPA 8260C variant, provide reliable detection of TCP at ppt levels. Elevated purge temperature, increased sample volume, and SIM detection combine to deliver high sensitivity, precision, and efficient sample throughput.

Reference

• National Toxicology Program, Department of Health and Human Services. 2016. Report on Carcinogens, Fourteenth Edition.
• U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response. 2014. Technical Fact Sheet – 1,2,3-Trichloropropane.
• U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response. 2008. Emerging Contaminant – 1,2,3-Trichloropropane.
• California Water Board, State Water Resources Control Board. 2017. State Adoption of 1,2,3-Trichloropropane MCL.
• Okamoto H.; Steeber W.; Remoy J.; Hill P.; Perera S. 2002. Determination of 1,2,3-Trichloropropane in Drinking Water by Purge and Trap GC/MS.
• Munch J., editor. 1995. USEPA Method 524.2: Measurement of Purgeable Organic Compounds in Water by Capillary Column GC/MS. Revision 4.1.
• U.S. Environmental Protection Agency. 2006. USEPA Method 8260C: Volatile Organic Compounds by GC/MS. Revision 3.