Detecting Emerging Contaminants in Reclaimed Water Using HILIC

A team of scientists from the University of Modena and Reggio Emilia, the University of Genoa, and the University of Lille have led a study on optimizing analytical methods for determining polar emerging contaminants (ECs) using a hydrophilic interaction liquid chromatography (HILIC)-based column. Their findings were published in the Journal of Chromatography A (1).

Sign advising of reclaimed irrigation water in use | Image Credit: © Simone - stock.adobe.com

Emerging contaminants (ECs) are a multiclass of chemical compounds with natural or synthetic origins, which can include industrial and agricultural additives (pesticides, fertilizers, flame retardants), personal care products (UV filters), and polyfluoroalkyl substances. In recent years, attention has been focused on persistent and mobile organic contaminants (PMOC), which are particularly polar ECs that can move through surface waters and spread in the environment due to their physicochemical characteristics. Analyzing these contaminants can be challenging, both because of the unsuitability of conventional chromatographic separation and because of their high affinity for an aqueous matrix, which hinders classical extraction methods. Specific water treatments are needed to eliminate these substances, and so careful evaluation of PMOC presence is vital when considering reclaimed water reuse for irrigation.

Hydrophilic interaction liquid chromatography (HILIC) is a highly suitable choice for determining polar hydrophilic compounds and offers an alternative to normal-phase (NPLC) and reversed-phase (RPLC) liquid chromatography. The technique operates by allowing analytes to interact with a hydrophilic stationary phase within a column and is valuable for analyzing complex mixtures that elute near the void in RPLC. This includes compounds with small or negative LogP values and hydrophilic, ionic, or ionizable functional groups (2). Further, the technique mitigates the solubility challenges of polar analytes typically found in NPLC. There are a wide variety of polar stationary phases available for use in HILIC, with efforts usually focused on the properties and applications of different materials such as bare silica and bonded-silica with polar groups (such as amide, diol, zwitterionic, macromolecules), ion exchangers, and mixed-mode phases.

In this study, the scientists optimized a liquid chromatography–mass spectrometry (LC–MS) method using a zwitterionic phosphorylcholine HILIC column to determine PMOCs in wastewater samples. An experimental design approach was taken to better understand the retention mechanisms of several polar compounds and find optimal operating conditions for detection and quantification. Eleven PMOCs were considered, including pesticides, artificial sweeteners, pharmaceuticals, and central nervous system stimulants. Various chromatographic variables were studied to assess their influence on peak areas, retention times, and separation efficiency; namely, the initial percentage of the organic mobile phase, temperature, flow rate, gradient time, acid percentage, and the type and concentration of two different salts.

Following these procedures, buffer type, flow rate, and initial percentage of organic mobile phase were identified as the most influential factors affecting retention, though effects were closely related to analytes’ chemical and physicochemical properties. The optimized instrumental method showed acceptable figures of merit, with recoveries ranging from 49–100% for all analytes except taurine (which may need a different experimental preprocessing step). The method also showed satisfactory precision in terms of relative standard deviation (RSD%), which was <10% for all analytes. When applied to the analysis of reclaimed water samples, nearly all target ECs were detected and quantified. This technique shows HILIC’s potential for this type of analysis. By fine-tuning chromatographic conditions for specific analytes, reliable EC detection in complex matrices, such as wastewater, was established.

References

(1) Strani, L.; Benedetti, B.; Cocchi, M.; et al. Optimization of an Analytical Method Based on the Use of Zwitterionic-Phosphorylcholine-HILIC Column for the Determination of Multiple Polar Emerging Contaminants in Reclaimed Water. J. Chromatogr. A 2025, 1741, 465605. DOI: 10.1016/j.chroma.2024.465605

(2) Hydrophilic Interaction Chromatography. ScienceDirect 2012. https://www.sciencedirect.com/topics/chemistry/hydrophilic-interaction-chromatography (accessed 2025-1-30).