{"id":83,"date":"2015-09-01T17:29:16","date_gmt":"2015-09-01T22:29:16","guid":{"rendered":"https:\/\/uwm.edu\/guo-lab\/?page_id=83"},"modified":"2025-08-29T13:28:48","modified_gmt":"2025-08-29T18:28:48","slug":"laboratory","status":"publish","type":"page","link":"https:\/\/uwm.edu\/guo-lab\/laboratory\/","title":{"rendered":"Laboratory"},"content":{"rendered":"

Analytical instruments and Research in Guo’s Lab<\/strong><\/span><\/h1>\n

A. Instruments for colloidal and nanoparticle characterization
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\u2022 Asymmetrical Flow Field-Flow Fractionation<\/em> (AFlFFF) system<\/h3>\n

The flow field-flow fractionation (FlFFF) is a chromatography-like technique capable of simultaneous separation and characterization of colloids, nanoparticles and macromolecules in aquatic environments.\u00a0 Our new asymmetrical flow field-flow fractionation system (Postnova) purchased through a NSF Major Research Instrument grant (NSF-MRI award #1233192<\/a>) can be coupled with a series of online detectors including a multiple angles light scattering (MALS) detector (21 angles), a UV absorbance detector, two fluorescence detectors with four different Ex\/Em wavelength combinations, a refractive index, ICP-MS (e.g., Stolpe et al<\/a>., 2010; Stolpe et al., 2013<\/a>; Zhou et al. 2016<\/a>), and other offline detectors\/instruments, such as spectrophotometer, 3D fluorometer (e.g., Zhou and Guo, JCA 2015<\/a>), EEM-PARAFAC (e.g., Lin and Guo, 2020 ES&T<\/a>; Lin et al., 2021, L&O<\/a>), gamma- & alpha-spectroscopy, and SEM\/TEM\/AFM, supporting and augmenting graduate education and ongoing research and allowing broader applications in aquatic and environmental sciences and other emerging topics.
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Contact Dr. Guo at guol@uwm.edu<\/a> for more information.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
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Postnova asymmetric flow field-flow fractionation system, coupled online with detectors including UV-absorbance, fluorescence with 4 different Ex\/Em combinations, refractive Index, Multi Angle Light Scattering (MALS), and others.<\/td>\nHow different sized-colloidal particles are separated using flow field-flow fractionation (from Postnova)<\/td>\n<\/tr>\n
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Separation of standard macromolecules using the FlFFF system (from Stolpe et al.) and changes in CDOM absorbance with membrane NMW cutoff (Zhou and Guo,<\/a> Journal of Chromatography A)<\/td>\nExamples showing the coupling between FlFFF separation techniques and fluorescence EEMs measurements. As shown in the EEM spectra, bulk DOM is highly heterogeneous with different chemical composition between DOM size fractions (from Zhou and Guo, 2015<\/a>, Journal of Chromatography A).<\/td>\n<\/tr>\n
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Coupling the FlFFF size-fractionation with EEM-PARAFAC analysis to elucidate PARAFAC-derived DOM components in individual water samples and to decipher changes in DOM composition and optical properties with molecular weight between samples across the river-lake and land-ocean interfaces (from Lin and Guo<\/a>, 2020, ES&T).<\/td>\nExamples showing the dynamic changes in PARAFAC-derived fluorescent DOM components with molecular weight within an individual DOM sample from the Milwaukee River (from Lin and Guo<\/a>, 2020, ES&T).<\/td>\n<\/tr>\n
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\u2022 SPLITT system:<\/strong> for size fractionation\/separation of suspended particles and\/or sediment\/soil for further chemical and isotopic characterization<\/em><\/p>\n

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\u2022 <\/em>Ultrafiltration systems<\/em><\/h3>\n

Our ultrafiltration systems have been widely used for size fractionation and isolating colloids or high molecular weight DOM for further chemical and isotopic characterization (Guo and Santschi<\/a>, 2007, pdf<\/a>; and Guo et al 2000<\/a>).\u00a0 These ultrafiltration units range from large engineering systems equipped with multiple spiral-wound or hollow-fiber cartridges capable of processing hundreds and thousands of liters of water (Guo et al. 1996, 1997; Cai et al., 2015<\/a>) to very small devices, such as centrifugal units and stirred cell units, for tracer studies and controlled laboratory experiments (e.g., Lin et al<\/a>. 2015; Yang et al.<\/a> 2015) and to quantify molecular size distributions of DOM and colloidal size spectra (e.g., Chen et al., 2004<\/a>;\u00a0 Xu and Guo, 2017<\/a>; Xu and Guo, 2018<\/a>; Yang et al., 2021<\/a>).<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
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Different ultrafiltration systems, ranging from centrifugal to stirred cells, large volume spiral wound cartridges and engineering systems<\/td>\nA schematic diagram showing components of ultrafiltration systems for isolating colloids\/naoparticles from natural waters (Guo and Santschi 2007).<\/td>\n<\/tr>\n
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Retentate vs. permeate from large volume ultrafiltration (up to 100 liters) for collecting nanoparticles \/macromolecules or sufficient amounts of freeze dried COM samples for isotopic and molecular characterization<\/td>\nAtomic force microscopy image of aquatic colloids (from Santschi et al., 1998, L&O)<\/td>\n<\/tr>\n
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Relationship between molecular weight (in kDa) and size (in nm) of macromolecular dissolved organic matter (from Guo and Santschi, 2007<\/a>, IUPAC Series).<\/td>\n

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\u2022 Effects of NOM on the toxicity of nanoparticles and metals
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Natural organic matter (NOM) isolated using ultrafiltration and model macromolecular organic matter with different functional groups were used to understand the interactions between DOM and nanoparticles (see examples in Kteeba et al<\/a>., 2017 ENPO;\u00a0 Baalousha et al.<\/a>, 2018, Environmental Science: Nano; Li et al., 2019, Environmental Pollution<\/a>, 252, 616-626.) and effects of NOM on surface properties and toxicity of nanoparticles in aquatic organisms (see examples below).<\/p>\n\n\n\n\n\n
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Examples showing changes in zeta-potential of ZnO nanoparticles in the presence of different NOM and organic compound classes (from Kteeba et al. 2017, Environmental Pollution<\/a>, ).<\/td>\nExamples showing the role of dissolved organic matter in remedying the toxicity of nanoparticles to Zebrafish (from Kteeba et al., 2017, Environmental Pollution<\/a>).<\/td>\n<\/tr>\n
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Mitigative effects of natural and model DOM with different functionalities on the toxicity of methylmercury (Me-Hg) in embryonic zebrafish (Li et al., 2019, Environmental Pollution<\/a>, 252, 616-626.)<\/p><\/div><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n