Date of Award

2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

A three-fold approach was taken to develop a method for the detection of heavy metals in different matrices and had to be performed sequentially. The first was to develop a method capable of quantifying lead in complex matrices by graphite furnace atomic absorption (GFAA). The developed method needed to meet specific analytical requirements, namely, to be robust, sensitive, and accurate. Initially, four different sample preparation methods were explored for the quantification of lead using Escherichia coli (E. coli) as a sample matrix. The sample preparation procedures attempted were acidic dilution, matrix modification, conventional heating digestion, and microwave assisted acid digestion (MAAD). It was determined that MAAD procedure was the optimal method as it had a percent recovery of 99.01 ± 9.46 and a reasonable relative standard deviation of 15.75%.The second goal of this study was to apply the developed method for the quantification of other analytes. This was successfully applied for the quantification of cadmium, chromium, copper, and zinc in E. coli and the percent recoveries for these elements were 109.8 ± 11.62%, 98.66 ± 9.483%, 99.23 ± 4.79%, and 100.3 ± 11.86%, respectively. The accuracy of these measurements was confirmed by analyzing certified reference materials (CRM). This CRM had cadmium chromium, copper, and zinc quantified by a third party, the European Commission. The percent differences between the experimental values determined in this study compared to the reference values was less than 10% for each analyte. Therefore, the MAAD method was deemed accurate for the analysis of these analyte The third goal of this study was to demonstrate the developed method’s versatility for the quantification of the analytes in different matrices, namely clinical and environmental samples. The clinical samples successfully analyzed in this study were human cataract lenses, removed during phacoemulsification at Loyola University Medical Center (LUMC). Cataracts are the leading cause of blindness in the world and are caused when the lifelong proteins within the lens start an opacification process. A total of 57 cataract samples were analyzed finding the following averages, 8.99  10-2  8.20  10-2 g/g cadmium, 3.32  6.04 g/g chromium, 3.16  1.83 g/g copper, 6.57  10.4 g/g lead, and 35.1  22.6 g/g zinc. These results were considered accurate based on the previous analysis of CRM, a secondary analysis by total X-ray fluorescence spectrometry (TXRF) and a comparison to previous studies quantifying heavy metals in either normal or cataract lenses. TXRF determined an average for copper to be 3.19  2.32 g/g, with a relative percent difference of 1.26%. Indicating the difference between the results determined by GFAA and TXRF to be negligible. This served as an example of how the developed method can be utilized for the quantification of heavy metals in a complex matrix. The environmental samples analyzed in this study were the plant Daucus Carota, or “Queen Ann’s Lace.” A plant naturally growing in the Midwest. This plant was collected from the Calumet industrial corridor, an area set aside within the city of Chicago for industrial uses and documented heavy metal pollution. Daucus Carota was collected from three different locations within the Calumet industrial corridor. It was determined that heavy metal bioaccumulation within Daucus Carota was dependent upon the location of its collection. Location 1, which was near a series of railways, had the highest concentrations determined for the analyte’s cadmium, copper, lead, and zinc while Location 3, close to a sewage treatment plant, had the highest chromium content. Following a secondary analysis, the TXRF samples concluded that its results for lead and copper were accurate. However, when examining the results for zinc, it was determined that GFAA overestimated the values or TXRF underestimated the values. Since zinc is not considered an environmental pollutant, it could be concluded that the analysis of heavy metal pollutants in environmental samples was successful. Overall, this study successfully developed an analytical method that can quantify multiple analytes in a wide range of different matrices. The method proved to be accurate, precise, sensitive, selective, and robust for clinical samples in form of cataract cell pellets and biological samples in form of plant tissues.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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