Senior Honors Projects, 2010-current

Date of Award

Spring 2015

Document Type

Dissertation/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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