Studies On The Application Of Modifid Carbon Paste Electrode

Electrochemical analysis has the advantage of quickness, convenience and sensitivity. Solid electrode, specially carbon paste electrode has significant advantage mainly in nontoxicity, smaller residual current, easiness to make up and to surface regeneration, wider potential range and low price. Therefore, carbon paste electrode was extensively used to determine inorganic ions and organic compounds.The main contents included the electrochemical behavior of cobalt, nitrite and ascorbic acid on carbon paste electrode or modified carbon paste electrode and its application. The results were shown as follows:1.Investigation on the determination of trace cobalt on carbon paste electrode and its application.The effects of the acidity and concentration of electrolytes, accumulation potential, accumulation time and scan rate on peak current of cobalt were studied to acquire optimum conditions. Simultaneous cyclic voltammetry, double potential step method and equal molar continual method were used to study the mechanism of the electrode reaction and propose its possible process of the reaction. Trace amounts of cobalt is determination by using a carbon paste electrode in a solution of 8.0X10-3mol/L NH3 ?Hp-Nl^Cl (PH=9.0) and 1.0 X Krtnol/L phea The peak potential of anode is 0.21V. A good linear range of cobalt is in 8.0 X 10^~4.0xlO'7mol/L with correlation coefficient of 0.9995.The detection limit is 2.0X 10" 9mol/L.The propose method has been applied to the determination of foodstuff tea leaf and drug on carbon paste electrode with satisfactory results. The recovery is 92.3%~ 104.0%.2.The electrochemical behavior of trace nitrite has been investigated with liner sweep voltammetry, chronoamperornetry method, cyclic vohammetry and others. Determination of trace nitrite on carbon paste electrode is in a buffer solution of 0.014 mol/L NazHPQ,?(PH=7.0) .The anodic peak potential of nitrite is 0.90V. The peak altitude are linearrelationship with NO2 concentrations in the range of 4.4 X 10*~1.7xiOr3mol/L with correlation coefficient of 0.9987.The detection limit is 2.2 X 10*mol/L.In the case, a lot of common ions do not interfere.3.Investigation on the determination of trace ascorbic acid on modified carbon paste electrode and its application.The determination of trace ascorbic acid by liner sweep voltammetry on modified carbon paste electrode. The ingredient of electrode and the effect on peak current was studied to acquire optimum conditions. The diffuse mechanism of the electrode reaction was studied by cyclic voltammetry and other methods.In l.Omol/L KC1, there was an excellent linearity between oxidation current and concentration of ascorbic acid in the range of 3.4 X 10~3~9.1 X 10^mol/L (r=0.9994).The detection limit is 5.7 X lO^mol/LThe method has been used for the determination of trace ascorbic acid in ascorbic acid tablet and orange juice with satisfactory results.