Reducing Carryover in Environmental Water Samples

Significance of the Topic

Solid phase microextraction and purge‐and‐trap methodologies are essential in environmental and food analysis for trace level detection of volatile organic compounds (VOCs). Reducing carryover improves laboratory throughput, data quality, and cost‐effectiveness, particularly in water and beverage testing where analyte‐free conditions are critical.

Objectives and Study Overview

This application note evaluates a patented sparge vessel bake innovation in the EST Analytical Evolution purge‐and‐trap system. The goal is to compare its effectiveness at minimizing carryover against a conventional hot water rinse approach in the analysis of water samples spiked with EPA 8260 VOC standards.

Methodology

The study employed a calibration curve from 0.5 to 200 ppb using EPA Method 8260 standards. Ten 200 ppb standards were analyzed, each followed by three blank runs. Carryover was assessed from the first blank after each standard based on GC/MS response.

Used Instrumentation

• EST Analytical Evolution Purge‐and‐Trap Concentrator with patented sparge vessel bake (US 8,075,842 B1)
• EST Centurion WS Autosampler
• Vocarb 3000 trap
• Agilent 7890A GC with Rxi-624Sil MS column (30 m × 0.25 mm I.D., 1.4 µm film)
• Agilent 5975C inert XL Mass Spectrometer

Main Results and Discussion

The patented dual‐bake approach (trap and sparge vessel) reduced average carryover for key VOCs (e.g., 1,2,4-trichlorobenzene and naphthalene) by nearly 50 % compared to a hot water rinse alone. Carryover levels for late-eluting compounds dropped from approximately 0.40–0.50 % to 0.25–0.28 %.

Benefits and Practical Applications

• Enhanced Productivity: Fewer blank runs and sample dilutions per sequence
• Improved Data Quality: Lower residual analyte levels reduce false positives and quantitation errors
• Cost Efficiency: Better utilization of instrument run time and reduced sample reruns

Future Trends and Possibilities

Integration of heated vessel cleaning steps may become standard in next‐generation purge‐and‐trap systems. Further developments could include automated temperature profiling and real‐time monitoring of residual VOCs to optimize bake cycles and instrument maintenance.

Conclusion

The EST Evolution system’s patented sparge vessel bake significantly lowers carryover relative to conventional rinsing methods, offering a robust solution for high‐throughput environmental laboratories seeking precision and efficiency in VOC analysis.

Reference

1. Analytical Trap Comparison for USEPA Method 8260C, Teledyne Tekmar, February 2012.