Author (Your Name)

Renee Blanchard, Colby College

Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Chemistry Dept.


D. Whitney King

Second Advisor

Thomas Shattuck

Third Advisor



The concentration of hydrogen peroxide in the Equatorial Pacific was determined fluorometrically using the horseradish peroxidase catalyzed dimerization of (p-hydroxyphenyl)acetic acid. Vertical profiles were obtained between 9 ON and 3 oS on a longitudinal transect along 140 oW during June and July of 1990 on the RN Wecoma. Peroxide concentrations ranged from 25-80 nmol/L at the surface and decreased to the detection limit of 1 nmol/L at a depth of about 200 meters. Diel variations of hydrogen peroxide in the surface waters were observed over the period of 8 days. The variation in surface concentration may be attributed to the dynamic equatorial current system, photochemical production, excretion by phytoplankton, and rain events. . In preparation for the cruise, a triiodide assay was adapted to more accurately determine the concentration of hydrogen peroxide stock solution used for standard additions. The selective dismutation of hydrogen peroxide versus organic peroxides by catalase, allows the differentiation of the two in my measurements. A series of experiments were performed using varying catalase concentrations to obtain better differentiation of hydrogen peroxide and organic peroxides. A flow system consisting of Teflon tubing, a pump and flow cell was designed to facilitate fluorescence measurements. The data collection was automated for more rapid signal acquisition using a DOH analog to digital converter and a Macintosh Plus computer.


Seawater -- Composition -- Pacific Ocean, Hydrogen peroxide

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