Sensitive Determination of Polycyclic Aromatic Hydrocarbons in Tap Water by Online Solid Phase Extraction and UHPLC

Significance of the topic

Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants with significant carcinogenic and mutagenic risks. Their presence in surface and drinking water demands fast, sensitive analytical methods to ensure compliance with regulatory limits and to protect public health.

Objectives and study overview

This work aimed to develop and validate a fully automated online solid-phase extraction (SPE) coupled with ultrahigh-performance liquid chromatography (UHPLC) method for trace analysis of the 16 EPA-priority PAHs in drinking water. The method was benchmarked against EPA procedures 550, 550.1, and 610, assessing speed, sensitivity, recovery, precision, and linearity.

Methodology and instrumentation

Online SPE enrichment and chromatographic separation were performed on an Agilent 1200/1260 Infinity Series platform. Key modules included:

• 1260 Infinity quaternary pump for SPE loading and column cleaning
• 1260 Infinity binary pump for gradient elution
• 1260 Infinity Flexible Cube accommodating two C18 enrichment cartridges
• 1260 Infinity autosampler with large-volume injection (up to 1,800 µL) and integrated cooler
• 1290 Infinity column compartment
• 1290 Infinity diode array detector (DAD) at 230 nm with 400 nm reference
• 1290 Infinity fluorescence detector with multiple excitation/emission channels

Samples (≤2 mL) were loaded onto Polaris C18-A cartridges and eluted through a ZORBAX Eclipse PAH analytical column using water–acetonitrile gradients at 25 °C.

Main results and discussion

The 16 PAHs were fully separated and detected within a 30-minute cycle time. Limits of detection ranged from 0.2 to 23 ng/L and quantification limits from 1 to 38 ng/L using a single 1,800 µL injection. Calibration curves were linear (R² > 0.998) across relevant concentration ranges. SPE recoveries averaged between 90% and 110% for most compounds; two high-molecular-weight PAHs showed slight deviations. Retention time and peak area reproducibility were better than 0.09% and 6% RSD, respectively.

Benefits and practical applications of the method

This automated online SPE-UHPLC workflow offers:

• Significant time savings versus conventional liquid-liquid or offline SPE (>60 minutes)
• Reduced organic solvent consumption and waste
• Minimal sample volumes (<2 mL)
• Sensitivity meeting or exceeding EPA maximum contaminant levels (e.g., benzo(a)pyrene at 0.2 µg/L)
• High reproducibility using alternating SPE cartridges

The method is ideal for routine monitoring in environmental and drinking water laboratories.

Future trends and potential applications

Emerging directions include coupling online SPE-UHPLC with mass spectrometry for broader compound coverage, miniaturizing cartridges for on-site analysis, and applying advanced data processing or machine learning for faster result interpretation. Investigation of PAH metabolites and transformation products in complex matrices also represents a promising area.

Conclusion

An automated online SPE-UHPLC method with UV and fluorescence detection has been established for rapid, sensitive, and robust determination of 16 PAHs in drinking water. The approach reduces manual handling, minimizes solvent use, and meets stringent regulatory requirements, providing an efficient alternative to traditional extraction techniques.

References

• Y. Watabe et al., Trace level determination of polycyclic aromatic hydrocarbons in river water with automated pretreatment HPLC, J. Sep. Sci. 2013, 36, 1128–1134
• US EPA Method 550.1, Determination of polycyclic aromatic hydrocarbons in drinking water, 1990
• US EPA Method 610, Polynuclear Aromatic Hydrocarbons, 1982
• D. Lerda, Polycyclic aromatic hydrocarbons factsheet, EU Commission JRC IRMM, 2012