Environmental Semivolatiles Using an Agilent Multimode Inlet for Maximum Sensitivity

Significance of Topic

The trace level determination of semivolatiles in water and environmental samples poses challenges due to analyte activity, background contamination and limited instrument sensitivity. Improving sensitivity extends detection limits, ensures compliance with regulatory methods and supports reliable monitoring of acids, bases, neutrals and pesticides in drinking and source waters.

Study Objectives and Overview

This application note evaluates the performance of an Agilent multimode inlet for gas chromatography mass spectrometry in three injection modes hot splitless cold splitless and large volume injection with solvent vent. The aim is to maximize signal to noise ratio for a suite of over 100 semivolatile compounds and demonstrate method flexibility with minimal hardware changes.

Methodology and Instrumentation

• Sample preparation by liquid solid extraction on C18 disks or cartridges or liquid liquid extraction with dichloromethane
• GC MSD system: Agilent 7890A gas chromatograph and 5975C triple axis detector mass selective detector
• Inlet: Agilent multimode inlet MMI with Agilent Helix single taper liner p n 5188-5397
• Injection modes: hot splitless 1 µL cold splitless up to 5 µL and large volume injection 25 µL with solvent venting
• Column: Agilent J W DB-5ms Ultra Inert 20 m × 0.18 mm ID 0.36 µm film thickness
• Retention time locked to phenanthrene-d10 at 11.000 minutes
• Calibration with custom mix of 18 analytes and internal surrogate standards over 0.1 ppb to 100 ppb range

Main Results and Discussion

Cold splitless injections increased signal to noise by 30 to over 100 percent for inert and active analytes compared to hot splitless. Inert compounds showed linear area gains up to 5 µL cold injections while active analytes reached optimal transfer by 3 µL. Large volume injection with solvent vent achieved at least 25 times lower detection limits with precision comparable to cold splitless. Optimization of inlet and source temperatures minimized analyte degradation and peak tailing improving sensitivity for polynuclear aromatic hydrocarbons and chlorinated phenols.

Practical Benefits and Applications

The multimode inlet enables rapid method development by allowing three injection techniques on a single deactivated liner without hardware changes. Cold splitless mode improves analyte transfer and reduces degradation. Large volume injection extends detection capabilities for low concentration environmental monitoring and QA QC applications.

Future Trends and Opportunities

• Expansion of large volume injection and solvent vent applications for complex matrices in environmental food and pharmaceutical testing
• Integration with retention time locking and deconvolution reporting software for high throughput compound identification
• Adoption of programmable temperature vaporizing inlets in routine analysis to standardize low level semivolatile methods

Conclusion

The Agilent multimode inlet provides enhanced sensitivity flexibility and productivity for semivolatile analysis in environmental laboratories. Cold splitless and large volume injection modes deliver lower detection limits and improved precision with minimal method development time compared to conventional hot splitless injections.

References

1 USEPA Method 525.2
2 Szelewski B Wilson Perkins Improvements in GC MSD for USEPA Method 8270 Agilent publication 5988-3072EN
3 Szelewski Fast Semivolatiles Analysis Agilent publication 5989-0207EN
4 Szelewski Part per Trillion Calibration Agilent publication 5989-6589EN