In present work, we have developed a system for detection and quantification of arsenic in water, based on surface plasmon resonance. Studies that we have done with self-assembled monolayers on gold substrate type Au(111) allowed us to evaluate the behavior and evolution of the substrate as it is reuse, which led us to perform a protocol for functionalization in aqueous medium to ensure autonomous and repetitive use of the substrate which makes it possible sensing concentrations close to 5 parts per billion. We have developed a novel self-functionalization system of monolayers on Au(111) for recognition and fixation of arsenic, that makes possible to use In situ of the substrate repeatedly (over 100 times).