Comparative study of Ag(I) selective poly(vinyl chloride) membrane sensors based on newly developed Schiff-base lariat ethers derived from 4,13-diaza-18-crown-6.

The six Schiff-base lariat ether chelates based on 4,13-diaza-18-crown ether, have been synthesized and explored as a neutral ionophores for preparing poly(vinyl chloride) based membrane sensors selective to silver(I). The addition of potassium tetrakis(4-chlorophenyl) borate and various plasticizers, viz., o-NPOE, DBP, DBBP, DOP and CN has been found to substantially improve the performance of the sensors. The best performance was obtained with the sensor no. 5 having membrane of chelate (A(6)) with composition (w/w) chelate (2.8%):PVC (45.7%):o-NPOE (48.6%):KTpClPB (2.8%). This sensor exhibits Nernstian response with slope 59.3mV/decade of activity in the concentration range 5.6 x 10(-8)-1.0 x 10(-1)M Ag(I), performs satisfactorily over wide pH range of (3.0-8.0) with a fast response time (12s). The sensor was also found to work satisfactorily in partially non-aqueous media up to 25% (v/v) content of acetonitrile, methanol or ethanol and can tolerate the concentration 1.0 x 10(-2)M of ionic (SDS, TBC) and nonionic (Triton X-100) surfactants. The proposed sensor can be used over a period of 4 months without significant drift in potentials. The response of the sensor was highly selective to Ag(+) over a large number of cations and it could therefore be used for Ag(+) estimation in blood of occupationally exposed persons.