The Determination Of Metal Ions Using Poly(Amino Acids)modified Glassy Carbon Electrodes

Lead and cadmium are harmful to the nervous system, immune system and genital system, copper is one of the essential microelements and an important part of protein and enzyme in human body. The change of metal ions in the body can reflect the immune and metabolism function directly, the determination of metal ions has great significance in bioscience and clinical medicine. Poly(amino acids) modified glassy carbon electrodes were prepared by cyclic voltammetry method. The electrochemical behaviors of lead was studied at poly(L-threonine) modified electrode. The electrochemical behaviors of lead and cadmium were studied at the poly(L-histidine) modified electrode. And the electrochemical behaviors of lead and copper were studied at the poly(L-glutamic acid) modified electrode. New methods for the determination of trace amount of metal ions were developed.During the whole research process, the major problems must be solved were: 1) the preparations and properties of poly(amino acids) modified glassy carbon electrodes; 2) the discussion of the electrochemical behaviors of lead at poly(L-threonine) modified electrode; 3)the discussion of the electrochemical behaviors of lead and cadmium at the poly(L-histidine)modified electrode; 4) the the discussion of the electrochemical behaviors of lead and copper at the poly(L-glutamic acid) modified electrode; 5) the determination of lead at poly(L-threonine) modified electrode; 6) the separate and simultaneous determination of lead and cadmium at the poly(L-histidine) modified electrode; 7) the separate and simultaneous determination of lead and copper at the poly(L-glutamic acid) modified electrode.The principle works are researched as follows:1. A poly(L-threonine) modified electrode was prepared by cyclic voltammetry. The electrochemical behaviors of lead was studied at poly(L-threonine) modified electrode. A new square wave anodic stripping voltmmetric method for the determination of trace amount of lead was developed. The deposition potential(-1.1V) was applied for 5 minutes. Within the scanning rate of 2m V/s in the range of-1.1~-0.2V in p H4.5 Na Ac-HAc buffer solution, thestriping peak current of lead was proportional to its concentration over the range of5.00×10-8~1.00×10-4mol/L. The detection limit was 5.0×10-9mol/L.2. A poly(L-histidine) modified electrode was prepared by cyclic voltammetry. The electrochemical behaviors of lead and cadmium were studied at the poly(L-histidine)modified electrode. A new square wave anodic stripping voltmmetric method for the simultaneous determination of trace amount of lead and cadmium was developed. The deposition potential(-1.3V) was applied for 5 minutes. Within the scanning rate of 2m V/s in the range of-1.3~-0.2V in Na Ac-HAc buffer solution at p H6.0, the striping peak current of lead and cadmium were well proportional to their concentrations over the range of5.00×10-8~7.50×10-4 mol/L. The detection limits are 1.0×10-9 mol/L for Cd2+ and 5.0×10-9mol/L for Pb2+.3. A poly(L-glutamic acid) modified electrode was prepared by cyclic voltammetry. The electrochemical behaviors of lead and copper were studied at the poly(L-glutamic acid)modified electrode. A new anodic stripping voltmmetric method was developed for the simultaneous determination of trace amount of lead and copper. The deposition potential(-0.8V) was applied for 5 minutes. The striping peak current of lead and cadmium were well proportional to their concentrations over the range of 5.00×10-8~1.00×10-4 mol/L,Within the scanning rate of 2m V/s in the range of-0.8~0.4V in Na Ac-HAc buffer solution at p H3.0. The detection limits are 5.0×10-9 mol/L for Pb2+ and 1.0×10-8 mol/L for Cu2+.