Surface-Enhanced Raman Spectroscopy and Chemometrics Offer Breakthrough in PAH Risk Analysis

In an effort to improve the quality of water for living organisms, a recent study conducted by researchers from Northwest University in China explored how using surface-enhanced Raman spectroscopy (SERS) combined with chemometric techniques can improve the detection and carcinogenic risk assessment of polycyclic aromatic hydrocarbons (PAHs) in water (1).

PAHs are chemicals that occur naturally in oil and gasoline (2). Humans are exposed to PAHs in many aspects of daily life. People consume PAHs when they eat grilled and charred meat, and they also breathe in PAHs from motor vehicle exhaust (2). Other sources of PAH consumption include the air, fumes from asphalt roads, and wood and cigarette smoke (2). PAHs are recognized as persistent organic pollutants, are notorious for their high teratogenic, carcinogenic, and mutagenic properties (1). With high octanol/water and sediment/water partition coefficients, these compounds pose severe threats to both human health and aquatic environments (1).

Clear Water drop with circular waves | Image Credit: © willyam - stock.adobe.com

As a result, the detection of PAHs in water remains challenging because of spectral interferences and the variability of environmental samples. To address these obstacles, the research team explored the integration of SERS technology with chemometrics, a combination that leverages the sensitivity of SERS and the computational power of chemometric modeling for enhanced analysis (1).

The researchers prepared 36 water samples, including lake, tap, and distilled water, as part of their study. Nano-silver particles (Ag NPs) were introduced into the samples to amplify the Raman signal, allowing for the precise detection of PAHs (1). The integrated strategy involved spectral preprocessing techniques to reduce interference, combined with variable selection algorithms to extract critical data points (1). These advancements enabled the creation of a robust random forest (RF) calibration model.

Several prominent PAHs were analyzed in this study. Some of these include phenanthrene (Phe), benzo[a]anthracene (BaA), and fluoranthene (Flu). When variable selection and spectral preprocessing were integrated into the RF model, the researchers found that there was an improvement in predictive accuracy and carcinogenic risk assessment (1).

For phenanthrene and benzo[a]anthracene, the wavelet transform, savitzky-golay, simplified partial least squares, variable importance measurement, with random forest (WT-SG-SiPLS-VIM-RF) model achieved good predictive performance, with a mean relative error of prediction (MRE_p) of 0.0646 and 0.0949, respectively, and a coefficient of determination of prediction (R_p²) of 0.9658 and 0.9537 (1). Similarly, the savitzky-golay, wavelet transform, simplified partial least squares, variable importance measurement, with random forest (SG-WT-SiPLS-VIM-RF) model yielded superior results for fluoranthene analysis (MRE_p = 0.0992, R_p² = 0.9551) (1).

When assessing the carcinogenic risk of PAHs, the wavelet transform, savitzky-golay, variable importance measurement, with random forest (WT-SG-VIM-RF) model stood out with an MRE_p of 0.0902 and R_p² of 0.9409, demonstrating its capability to deliver reliable predictions crucial for environmental risk management (1).

Overall, this study showcases the potential of combining SERS technology with chemometric modeling to address the limitations of traditional PAH detection methods. The integrated approach not only enhances the accuracy of quantitative analysis but also provides a reliable tool for assessing the carcinogenic risks associated with PAHs (1). By addressing the challenges posed by spectral interferences and leveraging the predictive power of machine learning models, the team has laid the groundwork for a more effective method of monitoring hazardous pollutants in water systems.

PAHs can pose a problem to human health, although the exact impact is still unclear. Some mixtures of PAHs are known to contain cancer-causing chemicals, and naphthalene, which is found in PAHs, can cause eye and throat irritation (2). Therefore, limiting PAH intake in humans is an important endeavor. Because water is regularly consumed by people globally, the development of new approaches to detect PAHs in water is critical. This research showcases the potential of SERS and chemometrics in environmental science while presenting new avenues for their application in other areas of pollutant analysis (1).

References

• Zhang, R.; Guo, M.; Li, M.; et al. Surface-enhanced Raman Spectroscopy Combined with Chemometrics for Quantitative Analysis and Carcinogenic Risk Estimation of Polycyclic Aromatic Hydrocarbons in Water with Complex Matrix. Chemom. Intell. Lab. Sys. 2025, 257, 105293. DOI: 10.1016/j.chemolab.2024.105293
• U.S. Environmental Protection, Polycyclic Aromatic Hydrocarbons (PAHs). EPA.gov. Available at: https://www.epa.gov/sites/default/files/2014-03/documents/pahs_factsheet_cdc_2013.pdf (accessed 2025-01-07).