Time filter

Source Type

Wu J.,Center for Advanced Water Technology | Zhang L.,Center for Advanced Water Technology | Yang Z.,Center for Advanced Water Technology
Critical Reviews in Analytical Chemistry

The occurrence of emerging contaminants in the aquatic environment is of increasing interest, as mordern sensitive techniques are employed worldwide for their determination. This review covers the current status and future prospects about the application of modern analytical instruments (such as GC-MS or LC-MS) for the analysis of emerging contaminants in aquatic system, in the past 2 years. The various sample preparation techniques will be compared and discussed as well. © Taylor and Francis Group, LLC. Source

Li S.,Center for Advanced Water Technology | Guo Z.,Center for Advanced Water Technology | Wu H.-F.,National Sun Yat - sen University | Liu Y.,Center for Advanced Water Technology | And 2 more authors.
Analytical and Bioanalytical Chemistry

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is challenging when it is directly applied to identify bacteria in water. This study demonstrates a rapid, sensitive, and selective technique for detection of Gram-positive bacteria in water. It involves a combination of membrane filtration (MF) and vancomycin-conjugated magnetite nanoparticles (VNPs) to selectively separate and concentrate Gram-positive bacteria in tap water and reservoir water, followed by rapid analysis of the isolates using whole-cell MALDI-MS. VNPs specifically recognize cells of Gram-positive bacteria, which serves as a basis for affinity capture of target Gram-positive bacteria. A two-step procedure of surface modification of bare magnetite nanoparticles was applied to synthesize VNPs. MF prior to VNP-based magnetic separation can effectively increase the enrichment factor and detection sensitivity and reduce time-consuming culture steps and the matrix effect for analysis of bacteria in MALDI-MS. The enrichment factor for the MF-VNP technique is about 6 × 104. A variety of bacteria, including Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, and Enterococcus faecium, were successfully analyzed from aqueous solutions and their mixtures with Gram-negative bacteria. The optimal conditions of the VNP/MALDI-MS technique, including selection of the MALDI matrix, the choice of cell-washing solution, and the VNP concentration, were also investigated. The capture efficiencies of Gram-positive bacteria with VNPs were 26.7-33.3%. The mass variations of characteristic peaks of the captured bacteria were within ±5 Da, which indicated good reproducibility of the proposed technique. The technique was applied to detect Gram-positive bacteria in tap water and reservoir water with an analysis time of around 2 h. The detection limit for Bacillus cereus, Enterococcus faecium, and Staphylococcus aureus was 5 × 102 cfu/ml for 2.0-l water samples. © 2010 Springer-Verlag. Source

Wu J.,Center for Advanced Water Technology | Qian X.,Center for Advanced Water Technology | Yang Z.,Center for Advanced Water Technology | Zhang L.,Center for Advanced Water Technology
Journal of Chromatography A

Matrix effect is a major problem when trace level pharmaceuticals in seawater were analyzed using solid-phase extraction (SPE) combined with high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS-MS). Therefore, efforts should be devoted to diminish matrix effect as much as possible. The present study investigates the matrix effect during the analysis of selected pharmaceutical residues (naproxen, ibuprofen, diclofenac and gemfibrozil) in seawater samples with ultra-high-performance liquid chromatography (UHPLC)-ESI low-energy collision-induced dissociation (CID) MS-MS. Solutions to reduce matrix effect were studied through optimization of SPE procedure and the employment of isotope-labeled analogues. Results showed that 30 mL of deionized water can efficiently diminish matrix effect and satisfactory absolute mean recoveries ranging from 73.5% to 120.5% were obtained in the optimized SPE condition. Isotope-labeled analogues employed as surrogates were found to be efficient to further compensate for matrix effect, with the relative mean recoveries ranging from 85.5% to 110.5%. The optimized method has been successfully applied for the analysis of target pharmaceutical residues in different seawater samples. © 2009 Elsevier B.V. All rights reserved. Source

Wu J.,Center for Advanced Water Technology | Hu R.,Center for Advanced Water Technology | Yue J.,Center for Advanced Water Technology | Yang Z.,Center for Advanced Water Technology | Zhang L.,Center for Advanced Water Technology
World Academy of Science, Engineering and Technology

Fecal sterol has been proposed as a chemical indicator of human fecal pollution even when fecal coliform populations have diminished due to water chlorination or toxic effects of industrial effluents. This paper describes an improved derivatization procedure for simultaneous determination of four fecal sterols including coprostanol, epicholestanol, cholesterol and cholestanol using gas chromatography-mass spectrometry (GC-MS), via optimization study on silylation procedures using N-O-bis (trimethylsilyl)-trifluoroacetamide (BSTFA), and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA), which lead to the formation of trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBS) derivatives, respectively. Two derivatization processes of injection-port derivatization and water bath derivatization (60 oC, 1h) were inspected and compared. Furthermore, the methylation procedure at 25 oC for 2h with trimethylsilydiazomethane (TMSD) for fecal sterols analysis was also studied. It was found that most of TMS derivatives demonstrated the highest sensitivities, followed by methylated derivatives. For BSTFA or MTBSTFA derivatization processes, the simple injection-port derivatization process could achieve the same efficiency as that in the tedious water bath derivatization procedure. Source

Discover hidden collaborations