An optical chemical sensor for mercury ion based on 2-mercaptopyrimidine in PVC membrane

An optical chemical sensor based on 2-mercaptopyrimidine (2-MP) in plasticized poly(vinyl chloride) (PVC) membrane incorporating (N,N-diethyl-5-(octadecanoylimino)-5H benzo[a]phenoxazine-9-amine (ETH 5294) and sodium tetraphenyl borate (NaTPB) for batch and flow-through determination of mercury ion is described. The response of the sensor is based on selective complexation of Hg2+ with 2-MP in the membrane phase, resulting in an ion exchange process between H+ in the membrane and Hg2+ in the sample solution. The influences of several experimental parameters, such as membrane composition, pH, and type and concentration of the regenerating reagent, were investigated. The sensor has a response range of 2.0x10(-9) to 2.0x10(-5) mol L-1 Hg2+ with a detection limit of 4.0x10(-1)0 mol L-1 and a response time of <= 45 s at optimum pH of 6.5 with high measurement repeatability and sensor-to-sensor reproducibility. It shows high selectivity for Hg2+ over several transition metal ions, including Ag+, Cd2+, Co2+, Cr3+, Cu2+, Fe3+, Mn2+, Ni2+, and common alkali and alkaline earth ions such as Na+, K+, Mg2+, Ca2+, and Pb2+. The sensor membrane can be easily regenerated with dilute acid solutions. The sensor has been used for the determination of mercury ion concentration in water samples.