A portable reflectometric photometer for quantitative enzyme immunoassay

A portable optoelectronic reflectometric photocolorimeter was designed. The photocolorimeter implements two operating modes (transmission and reflection), and its performance was tested in two systems of enzyme immunoassay for testosterone: microplate ELISA and membrane dot-ELISA. The detection threshold for microplate ELISA and membrane dot-ELISA was 0.1 and 0.6 ng/ml, respectively. The coefficient of correlation between the photocolorimeter readings and conventional photometric methods is r=0.999. Relative standard deviation of the results of photocolorimetric measurements (n = 4) within the optical density range of 0.03 to 1.00 ranged from 3.4 to 0.7%. The simple and versatile design of the photocolorimeter makes it appropriate for testing various substances both in laboratory settings and in the field.