Novel method for the determination of tetracycline antibiotics in bovine milk based on digital-image-based colorimetry

Solid-phase extraction was used to increase the intrinsic colour of tetracycline (TC), so that colorimetry could be employed as an analytical method for the detection of TC in milk. Digital-image-based colorimetry, a measurement based on capturing colour of solutions by a webcam camera, was coupled with an artificial neural network learning model for quantitative chemical analysis. The red, green, and blue values were used for data processing and were calibrated using values of standard solutions (from a database). The results were obtained directly as TC concentration. The colour intensity of the extracts was tested for accuracy using samples spiked with three TC concentrations. The average percentage recoveries were favourable in all samples and the relative accuracy of the method was between 91.9% and 105.0%. The method was validated by comparing the results with measurements performed using ultra-violet/visible spectrophotometry. There were no significant difference observed between the two methods.