Senior Honors Projects, 2010-current

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Award

Spring 2015

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Chemistry and Biochemistry

Advisor(s)

Daniel M. Downey

Abstract

Analytical methods for the determination of nitrogen and phosphorus nutrients (NO3-N, NH4-N and PO4-P) in sediment were studied with the goal of developing extraction steps compatible with analysis by ion chromatography (IC). Research focused on extractant solution composition, Dionex OnGuard® sample pretreatment cartridges for salt removal, and chromatographic resolution. Aqueous test samples, lake sediment samples and spiked lake sediment samples were analyzed. Dionex Ag, Ag/H, and H cartridges were studied for the pretreatment step. Silver (Ag) cartridges were found effective in removing >99% of interfering chloride ion to allow NO3-N determination by anion IC when 2 M KCl was used for sediment extraction. Ag cartridges were found to react and remove NH4-N, so an alternative extraction solution of 0.02 M SrCl2 was studied. Extraction by 0.02 M SrCl2 enabled anion IC analysis of NO3-N and cation IC analysis of NH4-N without further sample treatment, but this extraction method gave significantly lower values of nutrient (p < 0.05) than 2 M KCl extraction. Alternative chromatographic parameters utilizing increased eluent concentration were employed for the detection of NO3-N in sediment with interfering sulfate ion due to improved resolution of nitrate and sulfate peaks. Extraction with 0.02 M SrCl2 coupled to cation IC and phenate colorimetric methods gave similar results for NH4-N analysis in some sediments (p > 0.05), which demonstrated that the extraction step was the determining factor in nutrient analysis. Analysis of total phosphorus in the form of PO4-P was precluded by high sulfate and nitrate concentrations required for acid digestion of extracted sediment. Additional research is needed to develop IC methodology for NO3-N, NH4-N and PO4-P.

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