Preparation Of Chemically Modified Carbon Paste Electrode And Applications For Heavy Metal Ions And Melamine

This article mainly introduced chemically modified carbon paste electrodes and thepreparation methods of these electrodes, and then described their applications in all kinds ofchemistry. Carbon paste electrodes with DB18C6/β-CD, DB18C6/PVC and nano bariumferritea respectively as the modifiers were prepared. The heavy metal ions of Hg2+, Pb2+, Cu2+and melamine were detected by cyclic voltammetry and their electrochemical properties wereresearched, which obtained excellent detection performance. The main research works aredescribed as follows:1.Carbon paste electrode with DB18C6/β-CD as modifier is used to determine Hg2+, theoptimum ratio is DB18C6:β-CD:graphite quality=0.1:0.4:4. The characteristic peakappeared at0.385V in the NH3-NH4Cl buffer solution (pH is9.26), scanning speed100mV/s.Concentration of Hg2+and characteristic peak current are mostly linearly related inscope(1.0×10-8mol/L~1.0×10-4mol/L) of NH3-NH4Cl buffer solution. The linear correlationcoefficient is0.9962, and the detection limit is4.8×10-9mol/L. Combined with the advantagesof DB18C6and β-CD, the modified carbon paste electrode presented a series of attractivefeatures for the detection of Hg2+, such as high degree of selectivity and sensitivity, fastresponse and low detection limit. Therefore, this electrode can be used to detect Hg2+inwater samples.2.DB18C6/PVC modified carbon paste electrode was prepared and used to test theelectrochemical catalytic behavior of Pb2+. This electrode with part of graphite replaced byPVC, has not only overcome the disadvantages of water-soluble and easy to leak of DB18C6,but also bonded and enriched Pb2+, improved the detection performance. Under optimalconditions, the current of characteristic peak was linearly related to concentration of Pb2+in the range of1×10-9mol/L~1×10-4mol/L with a detection limit of8.4×10-10mol/L and thecorrelation coefficient is0.9978. DB18C6/PVC modified carbon paste electrode has excellentstability and repeatability in detection of Pb2+, fast and efficient.3.With the new type of nano barium ferritea as modifier, the carbon paste electrode wasprepared, by which, the detection of Cu2+in water samples and melamine can be detected byCyclic Voltammetry. The nano barium ferrite were characterized by scanning electronmicroscope. Meanwhile, the electrochemical behavior of Cu2+and melamine were studied indetail. Taking the impact of these factors: the buffer solution and pH, the proportion ofmodifier, scanning speed and range, accumulation time, the optimum experimental conditionswere determined. In the optimum experimental conditions, characteristic peaks of Cu2+andmelamine are obvious, a linear range from1.0×10-8mol/L~1.0×10-4mol/L, and the detectionlimits were respectively9.2×10-9mol/L and5.7×10-9mol/L. The recovery ratios were in therange of97.75%~101.60%and91.50%~98.25%by standard addition method. This modifiedcarbon paste electrode is easily prepared and low-cost, highly sensitive, has high value forpractical application.