Spot test with smartphone digital image analysis for determination of methadone in exhaled breath condensate

In this work, we explored the potential of the spot test combined with image analysis using smartphones as a rapid, simple, low-cost, and environmentally friendly method for identifying methadone concentration. Herein, a carbon-gold nanocomposite has been used to generate color variation at different concentrations of methadone. The data obtained from the digital image colorimetric method was compared with those from the UV-Vis spectroscopy as a standard technique. This method was also utilized for extensive optimization and validation procedures. Through image analysis, it can be obtained with the PhotoMetrix smartphone App. and single-variable calibration of collected images. This program computes and processes image histograms from the smartphone camera automatically to determine the concentration of methadone in biological samples. For further analysis, the multivariate calibration technique of PARAFAC can also be used on the images that were taken inside the MATLAB program.