The rapid increase in the number and volume of chemical substances being used in modern society has been accompanied by a large number of potentially hazardous chemicals being found in environmental samples. In Vietnam, the monitoring of chemical substances is mainly limited to a small number of known pollutants in spite of rapid economic growth and urbanization, and there is an urgent need to examine a large number of chemicals to prevent impacts from expanding environmental pollution. However, it is difficult to analyze a large number of chemicals using existing methods, because they are time consuming and expensive. In the present study, we determined 1153 substances to grasp a pollution picture of microcontaminants in the aquatic environment. To achieve this objective, we have used two comprehensive analytical methods: (1) solid-phase extraction (SPE) and LC-TOF-MS analysis, and (2) SPE and GC-MS analysis. We collected 42 samples from northern (the Red River and Hanoi), central (Hue and Danang), and southern (Ho Chi Minh City and Saigon-Dongnai River) Vietnam. One hundred and sixty-five compounds were detected at least once. The compounds detected most frequently (>40 % samples) at μg/L concentrations were sterols (cholesterol, beta-sitosterol, stigmasterol, coprostanol), phthalates (bis(2-ethylhexyl) phthalate and di-n-butyl phthalate), and pharmaceutical and personal care products (caffeine, metformin). These contaminants were detected at almost the same detection frequency as in developed countries. The results reveal that surface waters in Vietnam, particularly in the center of large cities, are polluted by a large number of organic micropollutants, with households and business activities as the major sources. In addition, risk quotients (MEC/PNEC values) for nonylphenol, sulfamethoxazole, ampicillin, acetaminophen, erythromycin and clarithromycin were higher than 1, which indicates a possibility of adverse effects on aquatic ecosystems.

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A comprehensive screening method for 311 organic compounds with a wide range of physicochemical properties (log Pow -2.2-8.53) in water samples was developed by combining solid-phase extraction with liquid chromatography-high-resolution time-of-flight mass spectrometry. Method optimization using 128 pesticides revealed that tandem extraction with styrene-divinylbenzene polymer and activated carbon solid-phase extraction cartridges at pH 7.0 was optimal. The developed screening method was able to extract 190 model compounds with average recovery of 80.8% and average relative standard deviations (RSD) of 13.5% from spiked reagent water at 0.20 μg L, and 87.1% recovery and 10.8% RSD at 0.05 μg L. Spike-recovery testing (0.20 μg L) using real sewage treatment plant effluents resulted in an average recovery and average RSD of 190 model compounds of 77.4 and 13.1%, respectively. The method was applied to the influent and effluent of five sewage treatment plants in Kitakyushu, Japan, with 29 out of 311 analytes being observed at least once. The results showed that this method can screen for a large number of chemicals with a wide range of physicochemical properties quickly and at low operational cost, something that is difficult to achieve using conventional analytical methods. This method will find utility in target screening of hazardous chemicals with a high risk in environmental waters, and for confirming the safety of water after environmental incidents.