Date of Graduation

Spring 5-2015

Degree Name

Bachelor of Arts

Department or Program

Environmental Studies

Number of Pages


First Advisor

Tom Wenzel


This thesis presents research on measuring trace concentrations of total phosphorus at the ppb level, using UV-visible spectrophotometry and colorimetry for the purpose of potential water monitoring. Total phosphorus was measured using ammonium molybdate and ascorbic acid reagents to form an intensely blue complex that can be measured within the visible spectrum of the UV-visible spectrophotometer. Each experimental trial generated a standard curve from three standards of known concentration (5, 10, and 20 ppb) and their measured absorbances at 880 nm. Eight trials were conducted, that either manipulated variables potentially affecting the accuracy and precision of the recorded absorbance or checked for reproducibility between trials. An acid digestion procedure was also tested in trials 14 and 15. Trials 11-14 and 16 had standard curves with R2 values of .95 or higher, demonstrating the capability of the protocol to generate linear standard curves, that could be used to measure samples of unknown concentration. However, the absorbance values for a specific concentration varied from trial to trial, necessitating the generation of a standard curve for each potential batch of samples. Although the results of this thesis are not enough to provide a reliable and efficient protocol, it provides valuable information that can lead the way for further research.

Components of Thesis

1 pdf file