Synthesis of hybrid thiol-functionalized SiO2 particles used for agmatine determination

In this study, we report on the fluorimetric method for the determination of biogenic amine agmatine based on hybrid SiO2 particles functionalized with thiol groups of 3-mercaptopropyltrimethoxysilane (MPTMS, SiO2-SH) and further conjugated with indicator dye o-phthaldialdehyde (OPA, SiO2-SH-OPA). Under optimal conditions, OPA reacted with agmatine and formed a fluorescent product in the alkaline media (pH 13). The fluorescence excitation and emission wavelengths were located at 340 and 430 nm. The relative fluorescence intensity was linear in the concentration range between 1.0 x 10(-7) and 1.0 x 10(-2) mol/L. Obtained SiO2-SH particles were characterized using infrared spectroscopy (FTIR), transmission electron microscopy, zeta potential and potentiometric titration.