Uma membrana carregadora plastificada foi preparada a partir de 2-metil-2,4-di(2-tienil)-2,3-diidro-1H-1,5-benzodiazepina (MTHB). Esta membrana é altamente sensível e seletiva a íons Ag + . O sensor mostra um intervalo dinâmico linear de 1,0 × 10 -6 -1,0 × 10 -1 mol L -1 , com inclinação Nernstiniana de (58,5±0,3) mV per década, e limite de detecção 5,0 × 10 -7 mol L -1 (~54 ppb). Apresenta rápido tempo de resposta, 10s, e pode ser usado por 8 semanas no mínimo, sem alterações consideráveis no seu potencial. O sensor proposto pode ser usado no intervalo de pH entre 4,0 e 8,0 e foi utilizado com sucesso, como eletrodo indicador, na titulação potenciométrica de Ag + com NaCl.A highly selective and sensitive plasticized membrane sensor for Ag + ions based on 2-methyl-2,4-di(2-thienyl)-2,3-dihydro-1H-1,5-benzodiazepine (MTHB) as membrane carrier was prepared. The sensor shows a linear dynamic range of 1.0 × 10 -6 -1.0 × 10 -1 mol L -1 , with a Nernstian slope of (58.5±0.3) mV decade -1 , and a detection limit of 5.0 × 10 -7 mol L -1 (~54 ppb). It has a fast response time of 10 s and can be used for at least eight weeks without any considerable divergences in its potentials. The proposed sensor revealed very good selectivities with respect to the most of common metal ions. The proposed sensor could be used in a pH range of 4.0-8.0. It was successfully used as an indicator electrode in potentiometric titration of Ag + with NaCl.Keywords: potentiometric sensor, Ag + sensor, PVC membrane, 2-methyl-2,4-di(2-thienyl)-2,3-dihydro-1H-1,5-benzodiazepine (MTHB)
IntroductionSilver plays no known natural biological role in humans, and possible health effects of silver are subject of dispute. Silver itself is not toxic but most of its salts are, and some may be carcinogenic. The toxicity of silver is characterized by a severe pulmonary edema, hemorrhage and necrosis of bone marrow, liver, and kidney. Long-term human exposure to silver salts or colloidal silver may cause argyria. Repeated exposure of animals to silver may produce anemia, cardiac enlargement, growth retardation and degenerative changes in the liver. Silver compounds were used successfully to prevent infection in World War I before the advent of antibiotics, and Silver compounds are still widely used externally today to accelerate healing in burn victims. Very low concentrations of silver are present in various complex samples like drinking water (5 μg L -1 , soil, rock, coal fly ash, air, cigarettes, alloys, plants, sea water etcetera). 1,2 Some techniques such as atomic absorption spectroscopy, 3 inductively coupled plasma, 4 spectroscopy with complexation agents 5 and Rayleigh light-scattering 6 have been used to determine amount of silver.Because of the increasing use of silver compounds in industry and medicine the quick determination of trace quantities of Ag + ion by simple methods is important in chemical, clinical and environmental analysis.Potentiometer monitoring based on ion-selective membrane sensor, as a simple method, offers several advantages such a...