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

Abstract

The aim of this study was to optimize a Liquid Chromatography Mass Spectrometry (LC-MS) method using a zwitterionic phosphorylcholine HILIC column for the determination of several Persistent and Mobile Organic Contaminants (PMOC) in wastewater samples. An experimental design approach was implemented to both better understand the retention mechanisms of several polar compounds and to find the optimal operating conditions for their detection and quantification. Eleven PMOCs, with logD_pH=7 ranging from -5.27 to 0.24, were considered, including pesticides, artificial sweeteners, pharmaceuticals, and central nervous system stimulants. Key chromatographic variables—such as the initial percentage of the organic mobile phase, temperature, flow rate, gradient time, acid percentage, and the type and concentration of two different salts— were studied to assess their influence on peak areas, retention times and separation efficiency. The results indicated buffer type, flow rate, and initial percentage of organic mobile phase as the most influential factors affecting retention, though the effects were closely related to the chemical and physicochemical properties of the analytes. The optimized instrumental method demonstrated acceptable figures of merit, with recoveries ranging from 49 % to 100 % for all analytes (except taurine, which may require a different experimental preprocessing step). The method also showed satisfactory precision (repeatability of the entire experimental procedure), in terms of Relative Standard Deviation (RSD %), which was <10 % for all analytes. The developed method was successfully applied to the analysis of reclaimed water samples collected in six wastewater treatment plants in two regions of northern Italy. All target ECs were detected and quantified, except for clenbuterol, terbutaline, acesulfame K and 2,4-dichlorophenoxyacetic acid, which were below the detection limit.