Automation of Liquid-Liquid Extraction methodologies using an on-line Gerstel MPS with Agilent 5977B High Efficiency Source

Importance of the Topic

Liquid-liquid extraction is a cornerstone technique in analytical chemistry for isolating trace organic contaminants from aqueous matrices. Automating this process addresses key challenges in routine testing laboratories, including reducing analyst intervention, improving reproducibility, lowering solvent consumption, and enhancing overall throughput and safety.

Objectives and Overview of the Study

This work evaluates the integration of an online Gerstel MultiPurpose Sampler (MPS) with an Agilent 5977B High Efficiency Source (HES) GC-MS system to automate liquid-liquid extraction workflows. Three classes of analytes—phenols, organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs)—are selected to compare manual and automated sample preparation methods in terms of time, solvent use, and analytical performance.

Methodology and Instrumentation

• Sample Preparation Platform: Gerstel MPS equipped with agitator (mVorx), evaporator (mVap), centrifuge (CF200), and PrepAhead module.
• Extraction Protocols: Automated addition of acid, standards, salts, derivatizing agents (PFBCl or BSTFA), mixing, phase separation, and direct injection of the organic layer.
• GC-MS Conditions: Agilent 7890B GC coupled to 5977B HES; run times varied by analyte class (phenols ~21 min, OCPs ~30 min, PAHs ~22 min).
• Throughput Modules: PrepAhead allows parallel sample processing, reducing idle time between injections.

Použitá instrumentace

• Gerstel MultiPurpose Sampler (MPS) with cooled injection system (CIS), agitator (mVorx), evaporator (mVap), and centrifuge (CF200).
• Gerstel MAESTRO software for scheduling and instrument control.
• Agilent 5977B High Efficiency Source GC-MS system.

Main Results and Discussion

• Time Savings: Annual sample preparation time reduced by over 1800 hours for phenols, with similar gains for OCPs and PAHs. Daily throughput increased from ~60 to 80–90 samples.
• Solvent Reduction: Automated workflows cut solvent use by ~23 L/month for phenols, ~155 L/month for OCPs, and ~70 L/month for PAHs, yielding cost savings >£6000/year.
• Sensitivity Improvement: The 5977B HES delivered up to an order of magnitude higher signal response versus a conventional extractor ion source, improving limits of detection.
• Analytical Performance: Calibration linearity (R2 >0.999) and precision (RSD ≤7%) were maintained or enhanced in automated protocols.
• Run Time Efficiency: Rapid cool-down of the GC inlet (CoolRPLUS) minimized cycle delays, enabling injection intervals as low as 2 min between runs.

Benefits and Practical Applications

• Significant reduction in analyst hands-on time and labor costs.
• Lower solvent and consumable usage enhances green chemistry compliance.
• Improved sample throughput supports large-scale monitoring programs.
• Enhanced reproducibility and data quality through standardized protocols.
• Compact laboratory footprint thanks to integrated automation modules.
• Increased safety by minimizing manual handling of corrosive reagents and solvents.

Future Trends and Possibilities

Automated sample preparation is poised to expand with modular additions such as solid-phase extraction and microextraction units. Integration with liquid chromatography-mass spectrometry platforms and real-time data analytics will enable adaptive workflows. Advances in robotics and AI‐driven method optimization promise further gains in efficiency, while push for sustainable solvents and miniaturization aligns with green analytical chemistry goals.

Conclusion

The coupling of the Gerstel MPS automation platform with an Agilent 5977B HES GC-MS demonstrates compelling benefits in speed, solvent consumption, and analytical performance for liquid-liquid extraction of environmental analytes. Its implementation streamlines laboratory operations, delivering reliable, high‐throughput data with reduced costs and improved safety.