A polystyrene based membrane of 3,4: 12,13-dibenzo-2,5,11,14-tetraoxo-1,6,1
0,15-tetraazacyclooctadecane shows a Nemstian response to Cd(II) ions over
a wide concentration range (3.16 x 10(6)-1.00 x 10(-1) mol L-1) with a Nems
tian slope of 29.8 mV/decade of concentration, between pH 2.0 and 6.0. This
electrode has been found to be chemically inert and of adequate stability
with a response time of 20s. The electrode gives reproducible results with
a lifetime of 130 days. The membrane works satisfactorily in a partially no
n-aqueous medium up to a maximum 35% (v/v) content of methanol and ethanol.
The practical utility of the proposed chemical sensor has been observed by
using it as end-point indicator in the titration of Cd(II) ions with EDTA.
The potentiometric selectivity coefficient values indicate that the membra
ne sensor is highly selective for Cd(II) ions over a number of cations. Sma
ll amounts of surfactants do not disturb the functioning of the sensor. Thi
s electrode has also been used to estimate cadmium ions in real samples.