Increased sample loading capacity for online SPE-HPLC analysis of PAHs in water

Significance of the topic

The analysis of polycyclic aromatic hydrocarbons (PAHs) in water is critical because PAHs are persistent environmental pollutants with significant mutagenic and carcinogenic potential. Regulatory methods such as EPA 610 require sensitive, accurate detection at trace levels. Online SPE-HPLC offers automation and improved detection limits compared to manual extraction.

Objectives and study overview

This work aimed to develop an online solid phase extraction (SPE)–high performance liquid chromatography (HPLC) method that allows rapid switching between direct injection and SPE injection using an auxiliary feed pump. The method was applied to selected PAHs (fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[g,h,i]perylene, indeno[1,2,3-cd]pyrene), with potential extension to all 16 EPA PAHs.

Methodology and instrumentation

A dual‐mode configuration permits either autosampler injection (5 µl) or large‐volume SPE loading via a feed pump (up to 1.8 ml) without manual replumbing. Reversed-phase chromatographic separation was carried out on a C18 PAH column with a water–acetonitrile gradient at 0.9 ml/min and 20 °C. Detection combined UV (230 nm, 254 nm) and fluorescence with programmed excitation/emission switching.

Instrumentation

• High-pressure binary pump (AZURA P6.1L HPG)
• Autosampler with advanced wash (AZURA AS 6.1L)
• DAD UV detector and fluorescence detector (Shimadzu RF-20A)
• Multiposition and high-pressure valves for SPE loading and elution
• Analytical column: NUCLEOSIL 100-5 C18 PAH (150 × 4 mm)
• SPE cartridge: Eurosil Bioselect 300-5 C8 (30 × 4 mm)
• Control software: ClarityChrom 8.5 with autosampler and PDA extensions

Main results and discussion

Precision was assessed by seven replicates of a 1:10³ diluted PAH standard. Retention time RSD was < 0.05 %, peak area and height RSDs were < 1 %. SPE recoveries ranged from 98.7 % to 115 %. Calibration demonstrated excellent linearity (R² ≥ 0.99985) over nanogram ranges. Direct injection LODs were 0.04–1.42 µg/l, LOQs 0.14–4.70 µg/l. Loading 1.8 ml onto the SPE cartridge via auxiliary pump improved LODs by 50–90 %, down to 0.01–0.40 µg/l.

Benefits and practical applications

The system enables flexible sample introduction from microliter to milliliter volumes, ensuring high throughput and automated preconcentration. Enhanced sensitivity meets regulatory requirements for trace PAH monitoring in environmental and industrial laboratories. The method reduces manual handling, minimizes contamination risk, and can be extended to a full suite of 16 EPA PAHs.

Future trends and potential applications

Further developments may include higher loading volumes for even lower detection limits, integration with mass spectrometric detection for increased selectivity, and miniaturization for field‐deployable monitoring. Automated multi-pollutant platforms could expand to include polar and semi-volatile organic contaminants in diverse matrices.

Conclusion

The presented online SPE-HPLC configuration allows seamless switching between direct and large-volume SPE injection, delivering robust precision, high recovery, and significantly enhanced sensitivity for PAH analysis in water. The approach is adaptable, automated, and compliant with EPA requirements.

References

• National Center for Biotechnology Information. Occurrence and persistence of PAHs in the environment. PMC7674206. Retrieved 2022-03-21.
• Illinois Sustainable Technology Center. Environmental pollutants: PAHs. Retrieved 2022-03-21.
• U.S. Environmental Protection Agency. Method 610: Determination of polynuclear aromatic hydrocarbons. 1984. Retrieved 2022-03-21.