Analyze More Semivolatile Samples per Shift Using Split Injection and an Rxi-5Sil MS Column

Importance of the Topic

Semivolatile organic compounds (SVOCs) are critical targets in environmental, industrial, and regulatory analyses due to their potential toxicity and persistence. Traditional splitless gas chromatography–mass spectrometry (GC–MS) methods for SVOC monitoring often suffer from long analysis times, frequent maintenance from column fouling, and variability between injections. Improving throughput while maintaining sensitivity and compliance with EPA Method 8270D can greatly enhance laboratory efficiency and data quality.

Objectives and Overview of the Study

This application note evaluates the performance of split injection combined with a low-bleed Rxi-5Sil MS column to accelerate SVOC analyses. Key aims include:

• Increasing sample throughput through faster oven cycling and split injection.
• Reducing maintenance frequency by limiting matrix load on the column.
• Demonstrating reliable detection, separation, and quantitation of EPA Method 8270D target compounds.

Methodology and Instrumentation

The study employed a comprehensive mixture of 95 SVOCs and surrogates to challenge chromatographic and mass spectral performance. Main methodological parameters:

• Sample Preparation: 8270 MegaMix, benzidines mix, benzoic acid standard, 1,4-dioxane, revised surrogate mixes, and internal standards diluted in methylene chloride.
• Injection: 1 µL split injection (10:1) at 270 °C using a precision inlet liner with wool; split vent flow 12 mL/min.
• GC Conditions: Agilent 7890A GC equipped with Rxi-5Sil MS column (30 m x 0.25 mm ID, 0.25 µm film). Carrier gas helium at 1.2 mL/min constant flow. Oven program: 70 °C hold 1 min → 285 °C at 28 °C/min → 305 °C at 3 °C/min → 320 °C at 30 °C/min (hold 1 min).
• MS Conditions: Agilent 5975C single quadrupole MS in EI mode (70 eV), scan range 35–550 amu, scan rate 5.36 scans/sec, transfer line 280 °C, source 270 °C, quadrupole 150 °C.

Used Instrumentation

• GC–MS System: Agilent 7890A GC and 5975C MSD.
• Column: Rxi-5Sil MS, low-polarity fused-silica (Crossbond 1,4-bis(dimethylsiloxy)phenylene dimethyl polysiloxane).
• Inlet Liner: Topaz 4 mm precision liner with quartz wool.
• Carrier Gas: Helium.
• Leak Detection: Restek electronic leak detector (optional).

Main Results and Discussion

The split injection method on the Rxi-5Sil MS column achieved baseline separation of all 95 target compounds within approximately 14 minutes. Notable findings include:

• Resolution of isomeric PAHs such as benzo[b]fluoranthene versus benzo[k]fluoranthene and critical phenolic and phthalate pairs.
• Lower column contamination and more consistent peak shapes due to reduced matrix load in split mode.
• Improved injection-to-injection reproducibility, with sensitivity and linearity meeting or exceeding EPA 8270D criteria.

Benefits and Practical Applications of the Method

Implementing split injection with an Rxi-5Sil MS column offers:

• Higher sample throughput: Faster oven ramps and split injections allow more analyses per shift.
• Extended maintenance intervals: Less non-volatile matrix on the column reduces downtime.
• Robust quantitation: Reliable trace-level detection for environmental monitoring, QA/QC in industrial laboratories, and compliance testing.

Future Trends and Potential Applications

Emerging directions include:

• Integration of fast GC techniques or multiplexed injection to further boost throughput.
• Coupling split injection methods with high-resolution or tandem mass spectrometry for non-targeted screening and enhanced compound identification.
• Development of field-deployable GC–MS platforms using split injection for on-site environmental assessments.

Conclusion

The combination of split injection and a robust Rxi-5Sil MS column delivers a high-throughput, low-maintenance approach for comprehensive SVOC analysis. This strategy aligns with regulatory guidelines, improves laboratory productivity, and ensures reliable data quality for environmental and industrial applications.

Reference

Featured Application: Extractable Semivolatile Organic Compounds on Rxi-5Sil MS. Restek Corporation, Lit. Cat. EVSS2679A-UNV (2018).