Initial Work for Automation of Polycyclic Aromatic Hydrocarbons in Water

Význam tématu

Environmental monitoring of polycyclic aromatic hydrocarbons (PAHs) in water is critical due to their toxicity, persistence and regulatory limits. Traditional manual liquid–liquid extraction (LLE) is time-consuming, solvent-intensive and poses health and safety risks. Automating and miniaturizing this step enhances laboratory throughput, reduces solvent usage and improves reproducibility.

Cíle a přehled studie / článku

This study aimed to develop an on-line automated method for extracting and quantitating eighteen PAHs from water samples. Collaborating with the UK Environment Agency, researchers miniaturized a conventional 1 L sample LLE into a 20 mL format using a GERSTEL Agitator and integrated the workflow into GC-MS analysis.

Použitá metodika a instrumentace

• Sample preparation: 18 mL water mixed with 500 µL cyclohexane in a 20 mL vial, agitated at 750 rpm on a GERSTEL Agitator.
• Post-extraction: addition of a polar solvent to break emulsions, sampling of the top organic layer.
• Injection: direct large volume injection (10 µL) from solvent layer into a GERSTEL Cooled Injection System (CIS).
• GC-MS conditions: separation on a 30 m × 0.25 mm ID DB-5MS UI column; detection on an Agilent 5977B mass spectrometer with High Efficiency Source (HES) in full-scan and selected ion monitoring (SIM) modes.
• Calibration: automated spiking of standards at 10, 25, 50, 100 and 200 ng/L by GERSTEL MPS, achieving linearity (R2 ≥ 0.995) without weighting.

Použitá instrumentace

• GERSTEL MPS XT dual-head sampler
• GERSTEL Agitator
• Anatune CoolRPLUS rapid GC oven cooling
• GERSTEL Cooled Injection System (CIS)
• Maestro control software with PrepAhead function
• Agilent 7890 GC coupled to 5977B MSD with HES

Hlavní výsledky a diskuse

• Throughput: automated PrepAhead enabled continuous sample prep during GC runs, allowing 55 samples per 24 h (over 100 % increase versus manual).
• Time savings: automation of 260 working days’ manual LLE, saving approximately 1 820 analyst hours per year.
• Solvent reduction: miniaturized extraction cut cyclohexane use from 5 mL to 0.5 mL per sample, saving ~70 L annually, with further potential down to 300 µL.
• Precision: example %RSD of 7.0 % for benzo(a)anthracene-d12 internal standard at low ng/L levels.
• Linearity and sensitivity: high correlation and detection comparable to original large-volume method, aided by 20–50× sensitivity gain of the HES source.

Přínosy a praktické využití metody

• Eliminates repetitive manual pipetting and associated RSI risks.
• Reduces solvent purchase, disposal costs and storage requirements.
• Lowers health and safety hazards in the laboratory.
• Minimizes sample volume needs and associated logistics.
• Provides reliable, reproducible data with minimal human error.

Budoucí trendy a možnosti využití

Further work could examine extraction efficiency in complex or turbid waters, potentially integrating an automated centrifuge (e.g. CF200) to address emulsion issues. Extending miniaturized LLE automation to other hydrophobic pollutants or coupling with in-line cleanup modules may broaden applicability. Advances in GC-MS interfaces and sample prep robotics will continue to drive green, high-throughput analytics.

Závěr

The automated, miniaturized LLE method for PAHs in water demonstrates significant gains in throughput, solvent economy and precision. Integration of GERSTEL and Anatune instrumentation under Maestro control allows reliable, reproducible quantitation of trace PAHs, offering a sustainable alternative to manual workflows.

Reference

Davis R., Leather P. Initial Work for Automation of Polycyclic Aromatic Hydrocarbons in Water. Chromatography Technical Note No AS171. Anatune Ltd & Environment Agency, UK, 2017.