C Wang

Investigation of Pharmaceuticals in Missouri Natural and Drinking Water Using High Performance Liquid Chromatography-Tandem Mass Spectrometry

A comprehensive method has been developed and validated in two different water matrices for the analysis of 16 pharmaceutical compounds using solid phase extraction (SPE) of water samples, followed by liquid chromatography coupled with tandem mass spectrometry. These 16 compounds include antibiotics, hormones, analgesics, stimulants, antiepileptics, and X-ray contrast media. Method detection limits (MDLs) that were determined in both reagent water and municipal tap water ranged from 0.1 to 9.9 ng/L. Recoveries for most of the compounds were comparable to those obtained using U.S. EPA methods. Treated and untreated water samples were collected from 31 different water treatment facilities across Missouri, in both winter and summer seasons, and analyzed to assess the 16 pharmaceutical compounds. The results showed that the highest pharmaceutical concentrations in untreated water were caffeine, ibuprofen, and acetaminophen, at concentrations of 224, 77.2, and 70 ng/L, respectively. Concentrations of pharmaceuticals were generally higher during the winter months, as compared to those in the summer due, presumably, to smaller water quantities in the winter, even though pharmaceutical loadings into the receiving waters were similar for both seasons.

Oxidative Removal and Kinetics of Fipronil in Various Oxidation Systems for Drinking Water Treatment

Fipronil, a pesticide gaining wide usage, was oxidized with common drinking water treatment disinfectants and oxidants; with a degradate identified using liquid chromatography-mass spectrometry. Oxidants investigated were free chlorine (HOCl/OCl(-)), monochloramine (ClNH(2)), chlorine dioxide (ClO(2)), and permanganate (MnO(4)(-)) at pH 6.6 and 8.6. Free chlorine, chlorine dioxide, and permanganate were reactive with fipronil to various degrees, whereas monochloramine was only marginally reactive. No oxidation products were observed for free chlorine, monochloramine, or chlorine dioxide. Oxidation by permanganate produced an identifiable degradate, fipronil sulfone, which was recalcitrant to further oxidation by permanganate. Fipronil sulfone could, however, be further degraded by free chlorine. Under typical conditions of water treatment, free chlorine was an effective oxidant for fipronil and fipronil sulfone, achieving partial removal at typical conditions. pH effects were observed for free chlorine, chlorine dioxide, and permanganate with more rapid oxidation occurring at pH 8.6 than at pH 6.6.

Investigation of removal of N-nitrosamines and their precursors in water treatments using activated carbon nanoparticles

N-nitrosamines have been detected in various water types. A strategy for removal of this group of compounds should be taken to reduce the health risks for humans. In this study, a fast and sensitive LC-MS/MS method was developed for quantitative analysis of nine N-nitrosamines and four precursors in a single sample. The Method Detection Limits (MDLs) in natural water ranged from 0.05 μg/L to 5 μg/L without using SPE pre-concentration. Three different types of activated carbon nanoparticles (NPs) (bamboo, charcoal and coconut shell as raw materials) were used to carry out removal experiments in two different pHs (pH 6.6 and 8.6). The results indicated that coconut shell-based activated carbon NPs had higher removal efficiency than the other two with a typical dosage of activated carbon NPs, at a typical contact time of 4 hours. No significant differences in removal efficiency between the two selected pH values were observed.