Grantee Research Project Results
2002 Progress Report: Speciation of chromium in environmental media using capillary electrophoresis with multiple wavlength UV/visible detection
EPA Grant Number: R828771C005Subproject: this is subproject number 005 , established and managed by the Center Director under grant R828771
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for the Study of Childhood Asthma in the Urban Environment
Center Director: Hansel, Nadia
Title: Speciation of chromium in environmental media using capillary electrophoresis with multiple wavlength UV/visible detection
Investigators: Stone, Alan T. , OMelia, Charles R.
Institution: The Johns Hopkins University
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2001 through September 30, 2002
Project Period Covered by this Report: October 1, 2001 through September 30, 2002
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objective of this research project is to develop the means of accurately characterizing chromium speciation in aqueous samples relevant to hazardous waste sites, using capillary electrophoresis (CE) with multiwavelength detection. Analytical separation, based on differences in the charge and hydrodynamic radii of analyte complexes, can efficiently resolve CrIII-containing low molecular-weight complexes from one another and from the CrVI species HCrO4- and CrO42-.
Progress Summary:
The new Beckman-Coulter capillary electrophoresis instrument was delivered in January 2002, and we now have 8 months of experience with its use. We expected that multiwavelength detection would be especially useful in the region between 300 and 600 nm, because this is the wavelength range employed most extensively by inorganic spectroscopists. Our experience is that molar absorptivities of CrIII complexes are typically not high enough in this range to be analytically useful. However, we have found that multiwavelength detection between 190 and 300 nm is enormously useful. Our current practice is to collect a full spectrum on each electromigrating peak. Calibration curves can be generated using the wavelength of maximum absorbance (max). Using this approach, our detection limits for dissolved CrIII complexes have improved more than 10-fold.
An illustrative electropherogram using detection at 229 nm is shown in Figure 1. This wavelength is close to max for most CrIII-containing compounds, but not close to max for CrVI species (switching to a different wavelength would dramatically increase the area of the peak corresponding to CrO42-). Complexes with four different synthetic chelating agents (nta, ida, hedta, and edta) are effectively distinguished from one another. Figure 1 also shows that a 2:2 dimer and 1:1 monomer of CrIII-nta can be distinguished effectively.
Figure 1. Electropherogram Illustrating the Analytical Separation of One CrVI-Containing Species and Five CrIII-Containing Species. The CE electrolyte contained 50 mM MOPS (pH 7.1) and 0.5 mM TTAB.
Calibration curves (see Figure 2) yield detection limits of 1 µM (50 µgCr.L-1) for HCrO4- at 214 nm and 3 µM (160 µgCr.L-1) for CrIII(OH2)3(ida)+ at 229 nm. The analyses shown in Figure 1 and for the HCrO4- calibration curve were performed using anion mode, and the calibration curve for CrIII(OH2)3(ida)+ was performed using cation mode.
Figure 2. Calibration Curves for HCrO4- (at 214 nm, anion mode) and CrIII(OH2)3(ida)+ (at 229 nm, cation mode). Both analyses employ a background electrolyte consisting of 50 mM acetate buffer (pH 4.8) and 0.5 mM TTAB.
Future Activities:
Our next 6 months of research will focus on the following tasks:
· Preparation and analysis of CrIII complexes with oxalate and citrate. These two naturally occurring chelating agents are released by the roots of most vascular plants. Plants growing on chromium-contaminated soils may potentially generate CrIII-oxalate and CrIII-citrate complexes.
· CrIII complexes with relatively weak chelating agents (e.g., oxalate) will be added to natural organic matter-containing solutions from the Great Dismal Swamp (Virginia). Using CE, we then will monitor loss of the CrIII-chelating agent peak and appearance of new CrIII-natural organic matter peaks.
· CrVI (chromate ion) also will be added to natural organic matter-containing solutions. In this case, loss of CrVI and the appearance of new CrIII-natural organic matter complexes will be monitored by CE.
Journal Articles:
No journal articles submitted with this report: View all 5 publications for this subprojectSupplemental Keywords:
chromium, capillary electrophoresis, toxics, inorganics, trace analysis, oxidation state, complexation., RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Waste, Water, Hydrology, Chemical Engineering, Environmental Chemistry, Geochemistry, Health Risk Assessment, Risk Assessments, Analytical Chemistry, Hazardous Waste, Physical Processes, Chemistry and Materials Science, Ecological Risk Assessment, Ecology and Ecosystems, Hazardous, Engineering, Chemistry, & Physics, Environmental Engineering, electrochemical technology, fate and transport, hazardous waste treatment, aquatic ecosystem, chemical exposure, contaminant transport, contaminant dynamics, fate and transport , analytical measurement methods, environmental risks, exposure, chemical composition, chemical detection techniques, ecotoxicological effects, adsorption, chemical kinetics, human exposure, chromium speciation, groundwater contamination, chemical releases, capillary elecrophoresis, capillary electrophoresis, hydrodynamics, groundwater, hazardous substance contaminationProgress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R828771 Center for the Study of Childhood Asthma in the Urban Environment Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828771C001 Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II
R828771C002 The Fate and Potential Bioavailability of Airborne Urban
Contaminants
R828771C003 Geochemistry, Biochemistry, and Surface/Groundwater Interactions
for As, Cr, Ni, Zn, and Cd with Applications to Contaminated Waterfronts
R828771C004 Large Eddy Simulation of Dispersion in Urban Areas
R828771C005 Speciation of chromium in environmental media using capillary
electrophoresis with multiple wavlength UV/visible detection
R828771C006 Zero-Valent Metal Treatment of Halogenated Vapor-Phase Contaminants in SVE Offgas
R828771C007 The Center for Hazardous Substances in Urban Environments (CHSUE) Outreach Program
R828771C008 New Jersey Institute of Technology Outreach Program for EPA Region II
R828771C009 Urban Environmental Issues: Hartford Technology Transfer and Outreach
R828771C010 University of Maryland Outreach Component
R828771C011 Environmental Assessment and GIS System Development of Brownfield Sites in Baltimore
R828771C012 Solubilization of Particulate-Bound Ni(II) and Zn(II)
R828771C013 Seasonal Controls of Arsenic Transport Across the Groundwater-Surface Water Interface at a Closed Landfill Site
R828771C014 Research Needs in the EPA Regions Covered by the Center for Hazardous Substances in Urban Environments
R828771C015 Transport of Hazardous Substances Between Brownfields and the Surrounding Urban Atmosphere
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
1 journal articles for this subproject
Main Center: R828771
108 publications for this center
20 journal articles for this center