Colorometric Determination of Catecholamines Using Silica Nanodots

The possibility of colorimetric determination of catecholamines using silica nanodots with a digital camera and smartphone is demonstrated. A lamp and a diode with emission wavelengths of 395 and 360 nm, respectively, are used as excitation sources. Color coordinates in the RGB, CMYK, and Lab systems, as well as some combinations thereof, are used as analytical signals. It is demonstrated that using a lamp as a source of ultraviolet radiation allows for achieving the best detection limits for all three catecholamines: 7, 0.1, and 1 μM when using a camera, and 12, 0.3, and 5 μM for dopamine, norepinephrine, and epinephrine, respectively, when using a smartphone. The data are obtained for the Euclidean distance analytical signal in the CMYK system. Using a camera and other color coordinate combinations as analytical signals can reduce the detection limits to 0.1 μM for epinephrine (coordinate combination L-a + b) and to 1 μM for dopamine (coordinate combination R + G + B). The pharmaceuticals “Dopamine-Ferein” (ZAO “Bryntsalov-A,” Russia), “Adrenaline Hydrochloride—Vial” (VIAL, China), and “Noradrenaline” (ZAO “EcoPharmPlus,” Russia) are analyzed. The results of colorimetric determination are in good agreement with the luminescence and HPLC analysis data.