1.
Magnetic solid phase extraction of sulfonamides based on carboxylated magnetic graphene oxide nanoparticles in environmental waters.
Gao, PS, Guo, Y, Li, X, Wang, X, Wang, J, Qian, F, Gu, H, Zhang, Z
Journal of chromatography. A. 2018;:1-10
Abstract
A magnetic nano-adsorbent material was prepared by functionalizing carboxylic group onto the granule surface of magnetic graphene oxide nanoparticles (CMGO), using in-situ co-precipitating method. The surface morphology was characterized by SEM and TEM. The CMGO was selected as the adsorbent for the magnetic solid phase extraction (MSPE) of sulfonamides (SAs) from environmental water samples, and the eluted analytes were determined by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A series of experimental parameters were optimized to improve the extraction efficiency such as amount of CMGO, extraction time, pH, ionic strength of the sample solution and desorption conditions. When the pH of water sample was 4.00, the extraction recoveries (ERs) for SAs were over 82.0% with 15.0 mg CMGO adsorption for 20 min. Under the optimized extraction conditions, linear range was obtained with coefficients of determination (R2)≥0.9983. The limits of detection for this proposed method were in the range of 0.49-1.59 ng/L, and the enrichment factors were 1320-1702 for eight SAs. The newly developed method was successfully applied to the analysis of trace SAs in real-world water samples, which provided satisfactory ERs in the range of 82.0-106.2% with RSDs less than 7.2%. Overall, it shows a great potential for the concentration of trace amine organic pollutions in complex matrices.
2.
Experimentally determined uranium isotope fractionation during reduction of hexavalent U by bacteria and zero valent iron.
Rademacher, LK, Lundstrom, CC, Johnson, TM, Sanford, RA, Zhao, J, Zhang, Z
Environmental science & technology. 2006;(22):6943-8
Abstract
Variations in stable isotope ratios of redox sensitive elements are often used to understand redox processes occurring near the Earth's surface. Presented here are measurements of mass-dependent U isotope fractionation induced by U(VI) reduction by zerovalent iron (Fe0) and bacteria under controlled pH and HCO3- conditions. In abiotic experiments, Fe0 reduced U(VI), but the reaction failed to induce an analytically significant isotopic fractionation. Bacterial reduction experiments using Geobacter sulfurreducens and Anaeromyxobacter dehalogenans reduced dissolved U(VI) and caused enrichment of 238U relative to 235U in the remaining U(VI). Enrichmentfactors (epsilon) calculated using a Rayleigh distillation model are -0.31% per hundred and -0.34% per hundred for G. sulfurreducens and A. dehalogenans, respectively, under identical experimental conditions. Further studies are required to determine the range of possible values for 238U/235U fractionation factors under a variety of experimental conditions before broad application of these results is possible. However, the measurable variations in delta(5238)U show promise as indicators of reduction for future studies of groundwater contamination, geochronology, U ore deposit formation, and U biogeochemical cycling.