Continuous flow analysis of lead (II) and mercury (II) with substituted diazacrown ionophore membrane electrodes

A novel flow cell for use with ion-selective membrane electrodes is reported in which the carrier stream is drawn through a tube that suppresses the pump noise. PVC membrane electrodes based on 7,16-dithenyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTODC), and 7,16-di-(2-thiopheneacetyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTAODC) for lead (II), and 7,16-dithenyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTDC) and 7,16-di-(2-methylquinolyl)-1,4,10,13-tertraoxa-7,16-diazacyclootadecane (DQDC), for mercury (II) were prepared and evaluated. The linear ranges were pPb: 5.5-3.0 (DTODC) and 6.0-2.0 (DTAODC); pHg: 5.5-3.0 (DTDC) and 4.5-2.5 (DQDC). With flow rate of 3 ml min-1 the repeatability of measurements was less than 5% RSD (n = 3). The system was applied to the determination of lead (II) and mercury (II) in spiked natural water samples.