Determination of Volatile Aromatic Compounds in Soil by Manual SPME and Agilent 5975T LTM GC/MSD

Significance of the Topic

Volatile aromatic compounds in soil present serious environmental and health challenges due to their toxicity and mobility in contaminated sites. Rapid and reliable on site detection is critical for emergency response, risk assessment, and remediation planning. Traditional laboratory methods demand laborious sample transport, storage, and solvent intensive extraction, leading to delays and increased error risk.

Objectives and Study Overview

This study aimed to develop and validate a portable workflow for quantifying 13 key volatile aromatic compounds in soil using manual solid phase microextraction (SPME) coupled with the transportable Agilent 5975T low thermal mass GC/MSD (LTM GC/MSD). Key goals included achieving low detection limits, robust recoveries across soil matrices, and rapid field deployment without compromising analytical performance.

Methodology and Instrumentation

Sample Pretreatment and SPME

• Soil blanks and field samples were spiked with target analytes at 5 to 50 µg/kg levels.
• A custom matrix modifying solution (pH 2, 36 g NaCl per 100 mL) minimized matrix effects and enhanced headspace release.
• SPME was performed with a PDMS 100 µm fiber at 60 °C for 10 minutes, followed by 1 minute desorption in a splitless inlet.

GC/MSD Conditions and Equipment

• Agilent 5975T LTM GC/MSD in manual injection mode with HP-5ms UI LTM capillary column (20 m x 0.18 mm, 0.18 µm).
• Temperature program: 45 °C (2 min), ramp 8 °C/min to 120 °C, ramp 20 °C/min to 150 °C.
• Helium carrier gas at 1.5 mL/min, electron impact ionization, full scan 45–250 u.

Main Results and Discussion

Calibration and Linearity

• Linear range from 5 to 50 µg/kg produced correlation coefficients above 0.99 for all analytes.
• Representative curves for toluene and 1,2,3-trichlorobenzene showed R2 values of 0.997 and 0.998 respectively.

Recoveries and Detection Limits

• Recoveries ranged from 65 to 109% across spiking levels with RSD below 5% for replicate preps.
• Method detection limit reached 1 µg/kg in real soil matrices without significant interference.

Field Sample Analysis and Software Screening

• Fresh garden soils spiked at 1 µg/kg confirmed method sensitivity and robustness.
• Custom deconvolution reporting software (DRS) enabled rapid target identification via library matching and retention time filters.

Benefits and Practical Applications

• Eliminates need for solvent extraction and extensive sample transport, reducing cost and turnaround time.
• Compact LTM GC/MSD and manual SPME workflow suits remote or emergency site monitoring.
• High sensitivity and selectivity for regulatory compliance and contamination assessment.

Future Trends and Opportunities

• Integration with automated fiber samplers and remote control could further streamline field analyses.
• Expansion to wider classes of VOCs and semivolatile compounds via different fiber chemistries.
• Coupling portable GC/MSD with cloud-based data platforms for real time contamination mapping and decision support.

Conclusion

The manual SPME approach combined with Agilent 5975T LTM GC/MSD provides a rapid, reliable, and field-deployable solution for soil volatile aromatic compound analysis. The method demonstrates excellent linearity, sensitivity, and robustness across diverse soil matrices, offering significant advantages for on site environmental monitoring.

Reference

1. Ingrida Seduikiene et al Solid phase microextraction of volatile aromatic hydrocarbons from soil Chemija(Vilnius) 2001 12(2)
2. EPA SW 846 Method 5035 Equilibrium headspace analysis of VOCs in soils