VOLUME 6 NUMBER 2 (July to December 2013)

by Adonis A. Yanos, Marianne N. Bautista, Mark Rickard N. Angeliaand Ernesto J. del Rosario*

Institute of Chemistry, College of Arts and Sciences,
University of the Philippines Los Baños, Laguna

The concentration of dissolved protein wasdetermined separately with biuret, bicinchoninicacid and Bradford reagents using conventionalabsorption spectrophotometry and digitalphotometry. The latter involved color analysis ofthe digital photographs using computer software (RGB analysisof image colors). Accuracy and precision of the digitalphotographic and conventional spectrophotometric methodswere compared using t-test and F-test. No significant differenceswere observed in determining protein concentration at 95 %confidence level based on RGB-derived parameters, namely %luminance, a*, and b*; similar results were obtained based onspectrophotometric and digital photometric methods. Resultsusing the digital photometric method were accurate andrepeatable. Comparison of average protein concentrationsobtained using the spectrophotometric and digital photometricmethods of a known solution showed that a fabricated light boxgave a higher precision than an assembled set-up. The resultsindicate the potential use of digital photometry, using a simpledigital camera with free-access software and a fabricated lightbox, as an alternative to absorption spectrophotometry in theaccurate determination of soluble protein concentration.