Maximizing Sample Throughput In Purge And Trap Analysis

Importance of Topic

The analysis of volatile organic compounds (VOCs) by purge and trap followed by GC/MS is vital for environmental monitoring, regulatory compliance and public health protection. Improving sample throughput while maintaining EPA Method 8260B criteria addresses the growing demands on high-volume laboratories and reduces delays caused by moisture interference, carry-over and long cycle times.

Objectives and Overview of the Study

This work evaluates a dual-concentrator configuration using the EST Centurion WS autosampler and two EST Encon Evolution purge and trap concentrators on a single GC/MSD system. The primary goals are:

1. Maximize sample throughput by reducing cycle time without altering EPA-required purge and trap conditions.
2. Maintain calibration linearity, accuracy and precision for water and soil matrices.
3. Demonstrate effective moisture management and carry-over reduction strategies.

Methodology and Used Instrumentation

The system employs two purge and trap concentrators in alternating mode to enable injections every 15 minutes. Key purge and trap settings include:

• Purge time 11 minutes at 40 ml/min He
• Dry purge 1 minute at 40 ml/min
• Desorb at 260 °C for 2 minutes at 12 psi
• Bake at 265 °C for 8 minutes with integrated sparge-vessel heater
• Moisture reduction trap (MoRT) placed upstream of analytical trap to eliminate dead volume and cold spots

GC/MS conditions (Agilent 7890/5975) feature split injection, RTX‐624 column, 45 °C→220 °C at 18 °C/min and constant helium flow at 0.8 ml/min.

Main Results and Discussion

Calibration over 1 ppb–200 ppb showed relative standard deviations below 12 % for all target VOCs in both water and soil matrices. Accuracy at 1 ppb ranged from 80 % to 120 %, with precision better than 10 % RSD for most compounds. The dual-concentrator setup enabled injections every 15 minutes, increasing throughput by 40 samples per instrument per 12-hour shift compared to single-concentrator systems. Moisture interference was minimized by the MoRT device, preserving peak symmetry and sensitivity, while vessel heating during bake eliminated carry-over without lengthening cycle time.

Benefits and Practical Applications

This configuration delivers:

• Enhanced productivity: 34 additional revenue-generating samples daily
• Consistent data quality within EPA Method 8260B requirements
• Reduced re-runs by effective moisture and carry-over control
• User-friendly operation via programmable internal standard delivery and soil-vial handling

Future Trends and Potential Applications

Emerging directions include integration of advanced moisture traps and miniaturized concentrators, real-time monitoring of purge efficiency, AI-driven optimization of cycle parameters and expansion to on-site mobile labs. Continued automation and instrument networking will further boost throughput, data transparency and remote control capabilities.

Conclusion

The dual-concentrator approach using the Centurion WS and Encon Evolution instruments significantly increases VOC analysis throughput while fully complying with EPA Method 8260B. Superior moisture management and carry-over reduction support high-quality, reproducible data and streamline environmental laboratory operations.