Philippine Science Letters
vol. 6 | no. 2 | 2013
published online September 20, 2013


Digital Photometric Determination of Protein Using Biuret, Bradford and Bicinchoninic Acid Reagents

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

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



The concentration of dissolved protein was determined separately with biuret, bicinchoninic acid and Bradford reagents using conventional absorption spectrophotometry and digital photometry. The latter involved color analysis of the digital photographs using computer software (RGB analysis of image colors). Accuracy and precision of the digital photographic and conventional spectrophotometric methods were compared using t-test and F-test. No significant differences were observed in determining protein concentration at 95 % confidence level based on RGB-derived parameters, namely % luminance, a*, and b*; similar results were obtained based on spectrophotometric and digital photometric methods. Results using the digital photometric method were accurate and repeatable. Comparison of average protein concentrations obtained using the spectrophotometric and digital photometric methods of a known solution showed that a fabricated light box gave a higher precision than an assembled set-up. The results indicate the potential use of digital photometry, using a simple digital camera with free-access software and a fabricated light box, as an alternative to absorption spectrophotometry in the accurate determination of soluble protein concentration.

*Corresponding author
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Submitted: May 29, 2013
Revised: August 4, 2013
Accepted: August 7, 2013
Published: September 20, 2013
Editor-in-charge: Evelyn Mae Tecson-Mendoza
Jose Hernandez Santos
Evelyn Mae Tecson-Mendoza