COMPARISON OF THE AGILENT 5977B MSD WITH HIGH EFFICIENCY SOURCE AND 7250 Q-TOF FOR ANALYSIS USING DISPERSIVE LIQUID-LIQUID MICROEXTRACTION OF SEMI VOLATILE ORGANIC COMPOUNDS

Significance of the Topic

Dispersive liquid–liquid microextraction (DLLME) is an emerging sample-preparation approach in environmental and industrial analysis, offering high enrichment factors and rapid throughput while minimizing solvent use and sample volume.

Objectives and Study Overview

This study compares two Agilent mass-spectrometric platforms—the 5977B single-quadruple MSD with a high-efficiency source (HES) and the 7250 quadrupole time-of-flight (Q-TOF)—for targeted analysis of semi-volatile organic compounds (SVOCs) using automated DLLME.

Methodology and Workflow

Water samples (8 mL) were spiked with EPA 8270 SVOC standards at varying concentrations (0–1.0 µg/L) and processed in batches of six via an automated DLLME protocol in 30 minutes per batch. Extracts (2 µL splitless) were analyzed on both GC–MS systems under full-scan electron impact ionization.

Used Instrumentation

• Agilent 7890B GC coupled to 5977B MSD with high-efficiency low-energy EI source
• Agilent 7890B GC coupled to 7250 Q-TOF MS
• GERSTEL Dual Head MPS robotic autosampler with 10 µL syringe
• GERSTEL QuickMix and Anatune CF200 robotic centrifuge
• Agilent MassHunter qualitative and quantitative software with PCDL Manager

Main Results and Discussion

• Signal-to-noise performance varied by compound and concentration: at 0.05 µg/L the Q-TOF outperformed the HES for several analytes, while at 1.0 µg/L both platforms achieved high S/N ratios (> 700).
• Accurate-mass extraction on the Q-TOF yields cleaner chromatograms and reduces interferences compared to a ±0.5 Da window on the single-quad.
• Both instruments delivered linear calibrations (R² > 0.99). Q-TOF benefits include mass-accuracy flags and ppm-based outlier detection.
• The low-energy EI mode on the Q-TOF enhances molecular-ion visibility for structural confirmation.

Benefits and Practical Applications

• Automated DLLME reduces solvent consumption, sample volume (6–8 mL), and preparation time (30 min/6 samples).
• High-efficiency sources on the 5977B enable detection limits down to 0.01 µg/L; Q-TOF extends sensitivity to sub-10 ng/L and offers accurate-mass confirmation.
• Suitable for targeted environmental monitoring, QA/QC in industrial analytics, and rapid screening workflows.

Future Trends and Potential Applications

• Integration of Q-TOF MS/MS fragmentation for advanced structural elucidation in unknowns investigations.
• Expansion of automated microextraction to other analyte classes (pesticides, emerging contaminants).
• Further miniaturization and on-line coupling of DLLME with high-resolution MS for real-time monitoring.

Conclusion

Both Agilent 5977B HES MSD and 7250 Q-TOF platforms effectively support automated DLLME of SVOCs, delivering robust sensitivity, high throughput, and reliable compound confirmation. The Q-TOF’s accurate-mass and low-energy EI capabilities offer enhanced confidence for targeted and untargeted analyses, while the single-quad HES provides cost-effective detection at sub-µg/L levels.

References

• Quick J. Exploring the advantages of automated sample preparation combined with GC-TOF MS for SVOC and pesticides analysis in environmental waters. ALS Environmental, Coventry, UK.
• Liscio C., Banks P. Comparison of the Agilent 5977B MSD with High-Efficiency Source and 7250 Q-TOF for DLLME of SVOCs. Anatune Ltd., Cambridge, UK.