Defense Date

11-21-2011

Graduation Date

Fall 2011

Availability

Immediate Access

Submission Type

thesis

Degree Name

MS

Department

Environmental Science and Management (ESM)

Committee Chair

H. M. "Skip" Kingston

Committee Member

Mizanur Rahman

Committee Member

Michael Tobin

Committee Member

John Stolz

Keywords

Chromium species, Dietary supplements, Hexavalent chromium, Isotope, SIDMS, Speciation

Abstract

In order to assess the benefit or toxicity of chromium in dietary supplements, trivalent chromium and hexavalent chromium must be measured and verified with mass balance (sum of both species equaling total chromium). This is necessary because dietary supplements report trivalent chromium, an essential trace element, as an ingredient, but hexavalent chromium, a toxic carcinogen, may also be present. Because trivalent chromium is stable in acidic conditions and hexavalent chromium in alkaline conditions, interconversions between species occur and increase the difficulty of quantification. Therefore, EPA Method 3060A was first performed to extract hexavalent chromium. Then, EPA Method 3052 was performed on the residue to digest the remaining trivalent chromium. Speciated Isotope Dilution Mass Spectrometry (SIDMS) with Ion-Exchange Chromatography-Inductively Coupled Plasma-Mass Spectrometry (IC-ICP-MS) was used to account for interconversions as well as determination of trivalent and hexavalent chromium concentrations in the studied samples. Mass balance indicated that the analyzed supplements contained hexavalent chromium ranging from 0 to 16% of the total chromium content.

Format

PDF

Language

English

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