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 Hg(2+) with 2-MP in the membrane phase, resulting in an ion exchange process between H(+) in the membrane and Hg(2+) 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 2.0 x 10(-9) to 2.0 x 10(-5) mol L(-1) Hg(2+) with a detection limit of 4.0 x 10(-10) mol L(-1) and a response time of < or = 45 s at optimum pH of 6.5 with high measurement repeatability and sensor-to-sensor reproducibility. It shows high selectivity for Hg(2+) over several transition metal ions, including Ag(+), Cd(2+), Co(2+), Cr(3+), Cu(2+), Fe(3+), Mn(2+), Ni(2+), and common alkali and alkaline earth ions such as Na(+), K(+), Mg(2+), Ca(2+), and Pb(2+). 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.