We report the characterization and determination of 2,6-dichloro-1,4-benzoquinone and three new disinfection byproducts (DBPs): 2,6-dichloro-3-methyl-1,4-benzoquinone, 2,3,6-trichloro-1,4-benzoquinone, and 2,6-dibromo-1,4-benzoquinone. These haloquinones are suspected bladder carcinogens and are likely produced during drinking water disinfection treatment. However, detection of these haloquinones is challenging, and consequently, they have not been characterized as DBPs until recently. We have developed an electrospray ionization tandem mass spectrometry technique based on our observation of unique ionization processes. These chloro- and bromo-quinones were ionized through a reduction step to form [M + H](-) under negative electrospray ionization. Tandem mass spectra and accurate mass measurements of these compounds showed major product ions, [M + H - HX](-), [M + H - HX - CO](-), [M + H - CO](-), and/or X(-) (where X represents Cl or Br). The addition of 0.25% formic acid to water samples was found to effectively stabilize the haloquinones in water and to improve the ionization for analysis. These improvements were rationalized from the estimates of pK(a) values (5.8-6.3) of these haloquinones. The method of tandem mass spectrometry detection, combined with sample preservation, solid phase extraction, and liquid chromatography separation, enabled the detection of haloquinones in chlorinated water samples collected from a drinking water treatment plant. The four haloquinones were detected only in drinking water after chlorination treatment, with concentrations ranging from 0.5 to 165 ng/L, but were not detectable in the untreated water. This method will be useful for future studies of occurrence, formation pathways, toxicity, and control of these new halogenated DBPs.

Formation of nine N-nitrosamines has been investigated when seven different source waters representing various qualities were each treated with eleven bench-scale disinfection processes, without addition of nitrosamine precursors. These disinfection treatments included chlorine (OCl-), chloramine (NH2Cl), chlorine dioxide (ClO2), ozone (O3), ultraviolet (UV), advanced oxidation processes (AOP), and combinations. The total organic carbon (TOC) of the seven source waters ranged from 2 to 24 mg x L(-1). The disinfected water samples and the untreated source waters were analyzed for nine nitrosamines using a solid phase extraction and liquid chromatography-tandem mass spectrometry method. Prior to any treatment, N-nitrosodimethylamine (NDMA) was detected ranging from 0 to 53 ng x L(-1) in six of the seven source waters, and its concentrations increased in the disinfected water samples (0-118 ng x L(-1)). N-nitrosodiethylamine (NDEA), N-nitrosomorpholine (NMor), and N-nitrosodiphenylamine (NDPhA) were also identified in some of the disinfected water samples. NDPhA (0.2-0.6 ng x L(-1)) was formed after disinfection with OCl-, NH2Cl, O3, and MPUV/OCl-. NMEA was produced with OCl- and MPUV/OCl-, and NMor formation was associated with O3. In addition, UVtreatment alone degraded NDMA; however, UV/ OCl- and AOP/OCl- treatments produced higher amounts of NDMA compared to UV and AOP alone, respectively. These results suggest that UV degradation or AOP oxidation treatment may provide a source of NDMA precursors. This study demonstrates that environmental concentrations and mixtures of unknown nitrosamine precursors in source waters can form NDMA and other nitrosamines.

Coming clean? Liquid chromatography–ESI tandem mass spectrometry is used to detect 2,6‐dichloro‐1,4‐benzoquinone (see picture) in drinking water treated with chlorine or chloramine.

No abstract

Monolithic silica capillary columns were prepared by a sol-gel process in fused-silica capillaries with an inner diameter of 50 microm and were modified by coating of cellulose tris(3,5-dimethylphenylcarbamate). Influences of the factors in the modification process on enantiomer separations were investigated. The prepared columns were used to perform enantiomer separations by CEC. Fifteen and two pairs of enantiomers were separated under aqueous and nonaqueous mobile phases, respectively, and most of them were baseline-separated with very high column efficiencies. The Van Deemter curve was found flat under high linear velocity of the mobile phase, which indicated favorable kinetic properties of the prepared columns. Baseline separation of a pair of enantiomers was achieved in 90 s with high-column efficiency by short-end separation under high voltage.

N-nitrosodiphenylamine (NDPhA) is a disinfection byproduct (DBP) in drinking water. However, it is not known what governs the formation of NDPhA and which precursor(s) in the raw water is responsible for its formation. We report here diphenylamine (DPhA) as a key precursor of NDPhA, and we describe the effect of water pH and chloramination conditions on the formation of NDPhA. To identify precursors of NDPhA, raw water samples were collected from the same drinking water system in which NDPhA was previously detected. Analysis of the raw water samples showed the presence of 1.3 ng/L of DPhA and no detectable NDPhA. Seven hours after the treatment of the raw water with chloramines, the concentration of DPhA decreased to 0.4 ng/L with corresponding formation of NDPhA (0.4 ng/L). Controlled experiments involving chloramination of DPhA in water showed that chloramines were essential to the formation of NDPhA, and that increasing the pH from 4 to 10 resulted in 64-fold enhancement in NDPhA formation. Removal of DPhA and formation of NDPhA was found by mass imbalance, which led to the identification of two new DBPs, phenazine (MW 180 Da) and a chlorinated phenazine derivative (MW 216 Da), using liquid chromatography tandem mass spectrometry and gas chromatography mass spectrometry. Both new DBPs were detected only in the treated water and not in the raw water. Phenazine and N-chlorophenazine have never been reported as DBPs and neither their occurrence in drinking water nor their health effects are known.

Monolithic materials have become a well-established format for stationary phases in the field of capillary electrochromatography. Four types of monoliths, namely particle-fixed, silica-based, polymer-based, and molecularly imprinted monoliths, have been utilized as enantiomer-selective stationary phases in CEC. This review summarizes recent developments in the area of monolithic enantiomer-selective stationary phases for CEC. The preparative procedure and the characterization of these columns are highlighted. In addition, the disadvantages and limitations of different monolithic enantiomer-selective stationary phases in CEC are briefly discussed.

We report a hydrophilic interaction liquid chromatography (HILIC) separation with tandem mass spectrometry (MS) detection method for analysis of seven urinary estrogen conjugates. HILIC separation employing a mobile phase with high organic solvent content resulted in enhanced electrospray ionization efficiency and MS sensitivity compared with reversed-phase (RP) LC-MS methods. Solid-phase extraction (SPE) was used to further improve the limit of detection and to eliminate interferences for the analysis of urine samples. No hydrolysis or derivatization was required in the sample pretreatment. This SPE/HILIC-MS/MS method provided limits of quantification (LOQs at S/N = 10) for the seven conjugates ranging from 2 to 1000 pg/mL with only 1 mL of urine sample, representing an improvement of 1 order of magnitude over the RPLC tandem MS methods previously reported. This method provided a linear dynamic range of 3 orders of magnitude, recovery of 92-109%, intraday accuracy of 84-109%, intraday precision of 1-14%, interday accuracy of 80-111%, and interday precision of 1-22%. We have successfully applied this technique to determine the seven estrogen conjugates in urine samples of a pregnant woman and found unique concentration changes of six estrogen conjugates at different stages of pregnancy while the concentration of estriol-3-glucuronide (E3-3G) remained constant. We further studied the profiles of individual estrogen conjugates in breast cancer patients before and after treatment and found patient-dependent effects of aromatase inhibitor treatment on estrogen phase-II metabolism, which have not been reported previously. This study demonstrates the potential clinical application of the HILIC-MS/MS technique for sensitive monitoring of the changes of urinary estrogen conjugates in a clinical setting.