PREPARATION OF DITHIOCARBAMATE CHELATING RESIN MODIFIED GRAPHITE ELECTRODE AND ITS APPLICATION TO THE DETERMINATION OF SILVER

To prepare the modified electrode,pure graphite electrode was polished with Al2O3 and polar-activated with an acid mixture of conc.HNO3 and conc.H2SO4 in ratio of 1 to 1.It was then soaked for a moment in 10 μL of 1 g·L-1 solution of PVC in cyclohexanone.After taking out from the solution and dried for 30 min under IR-radiation,the electrode was reacted in a solution containing piperazine,K3PO4 and DMF in the ratio of 2 to 1 to 8.Finally the electrode was reacted with CS2 in the presence of NaOH,and washed with water to neutrality.Better sensitivity and selectivity were obtained by the modified graphite in the determination of Ag+-ion,as compared with the unmodified electrode.The optimum conditions for the determination were described as follows:base solution 1.0 mol·L-1 KCl,acidity pH 1.7,time of enrichment 15 min,rate of scanning 100 mV·s-1.Linear relationship between the peak current (ip) and concentration of Ag+-ion was kept in the range of 1.0×10-8-1.0×10-5mol·L-1 with a detection limit of 5.0×10-9mol·L-1 of Ag+ ion.