Large Volume Splitless Injection Using an Unmodified Split/Splitless Inlet and GC-TOFMS for Pesticides and Brominated Flame Retardants

Importance of the Topic

The monitoring of trace-level pesticides and brominated flame retardants in drinking water is critical for ensuring public health and regulatory compliance. Large volume splitless injection enhances sensitivity in gas chromatography by introducing higher amounts of analytes onto the column, yet conventional methods often require specialized injection ports and lengthy extract concentration steps. Concurrent solvent recondensation–large volume splitless injection (CSR-LVSI) offers a practical adaptation that can be implemented with an unmodified split/splitless inlet.

Objectives and Study Overview

This study evaluates CSR-LVSI for the analysis of pesticides and polybrominated diphenyl ethers (PBDEs) in drinking water following US EPA Method 527. Two experimental approaches were compared:

• CSR-LVSI without extract concentration to assess recovery, linearity, and time savings.
• CSR-LVSI combined with extract concentration for enhanced detection limits in an environmental water sample.

Methodology

Samples of deionized water were fortified at 0.1 and 1.0 µg/L levels with pesticide and PBDE standards and extracted via solid phase extraction on a polystyrene-divinylbenzene disk. Extracts were dried and diluted to 25 mL, or further concentrated to 1 mL in the second experiment. Calibration standards ranging from 25 to 1,000 pg on-column established linearity. CSR-LVSI employed a fast autosampler injection of 12.5 µL into a split/splitless inlet held at 250 °C, using a deactivated guard pre-column to trap solvent and focus analytes.

Used Instrumentation

• Agilent 6890 GC split/splitless inlet (unmodified)
• Agilent 7683 autosampler with 25 µL large volume syringe
• Deactivated 5 m × 0.53 mm ID pre-column and 15 m × 0.25 mm Rxi-5Sil MS column
• LECO Pegasus GC-TOFMS with spectral deconvolution software

Results and Discussion

Without extract concentration, calibration was linear down to 25 pg on-column (0.05 µg/L), and average recoveries at 1.0 µg/L and 0.1 µg/L fortified levels were 94% and 80%, respectively. All method criteria were met except a few late-eluting PBDEs at the lowest level. Eliminating concentration reduced sample preparation by over one hour. In a real water sample from a remediated creek, combining CSR-LVSI with extract concentration detected atrazine, Kepone, and PBDEs at sub-ppt to ppq levels.

Benefits and Practical Applications

CSR-LVSI on a standard inlet:

• Maintains sensitivity and chromatographic performance without hardware modification.
• Reduces or eliminates laborious concentration steps, increasing sample throughput.
• Offers flexibility to achieve lower detection limits when needed.

Future Trends and Potential Uses

Further adoption of CSR-LVSI may include integration with automated sample preparation platforms, extension to other low-level analytes in complex matrices, and pairing with multidimensional GC or high-resolution MS for enhanced selectivity and robustness in environmental and food safety laboratories.

Conclusion

CSR-LVSI using an unmodified split/splitless inlet is a technically viable approach for routine analysis of pesticides and flame retardants in water. It streamlines workflow by reducing preparation time and can be combined with extract concentration to reach ultra-trace detection limits.

Reference

1. Magni P., Porzano T. Journal of Separation Science 26 (2003) 1491.
2. US Patent 6,955,709 B2.
3. Biedermann M., Fiscalini A., Grob K. Journal of Separation Science 27 (2004) 1157.
4. US EPA Method 527, April 2005.
5. Thermo Scientific application of CSR-LVSI for drugs of abuse screening.
6. Thermo Scientific analysis of pesticides and PCBs with CSR-LVSI.
7. Increased sensitivity for PCBs in water and soil by GC-ECD using large volume splitless technique.
8. US EPA Mid-Atlantic Superfund Centre County Kepone site.