This paper provides a methodology for the design, development, and technical validation of an
open-source colorimeter using the closed reflux COD method (EPA method 5220D). This approach is evaluated for its potential to reduce the cost of equipment to perform colorimetric COD and the results
are discussed to provide conclusions about futuredevelopment of open-source analytical tools.
Whereas a previous open-source colorimeter, the IORodeo Educational Colorimeter Kit [33], was
developed for use in the education environment, the instrument presented here is purpose-built to
perform this single analysis so as to determine the efficacy of applying the open-source methodology
to development of research-grade, bespoke instruments in a research environment. The colorimeter
was selected because of its simplicity and utility, making it an ideal instrument to launch an
investigation intothis methodology