A Novel Potentiometric Membrane Sensor Based on Aryl Palladium Complex for Selective Determination of Thiocyanate in the Saliva and Urine of Cigarette Smokers

A highly selective potentiometric sensor for thiocyanate ion based on the use of a newly synthesized organo‐palladium ion exchanger complex dispersed in a plasticized poly(vinyl chloride) membrane is described. The sensor displays a Nernstian response (−57.8±0.2 mV decade −1 ) over a wide linear concentration range of thiocyanate (1.0×10 −6 –1.0×10 −1 mol L −1 ), low detection limit (6.3×10 −7 mol L −1 ), fast response (20 s), stable potential readings (±0.4 mV), good reproducibility (±0.9%), long term stability (8 weeks), high precision (±0.7%) and applicability over a wide pH range (4–10). Negligible interferences are caused by F − , Cl − , I − , Br − , NO 3 − , NO 2 − , CN − , SO 4 2− , S 2 O 3 2− , PO 4 3− , citrate, acetate and oxalate ions. Under hydrodynamic mode of operation (FIA), the calibration slope is −51.1±0.1 mV decade −1 , the linear response range is 1.0×10 −5 –1.0×10 −1 mol L −1 SCN − and the sample throughput is 40–45 per hour. The sensor is satisfactory used for manual and flow injection potentiometric determination of SCN − in the saliva and urine of cigarette smokers and non smokers. The data agree fairly well with results obtained by the standard spectrophotometric technique. Direct potentiometry and potentiometric titration of SCN − with Ag + are also monitored with the sensor.